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Sample records for residual amplitude modulation

  1. Residual Amplitude Modulation in Interferometric Gravitational Wave Detectors

    CERN Document Server

    Kokeyama, Keiko; Korth, William Z; Smith-Lefebvre, Nicolas; Arai, Koji; Adhikari, Rana X

    2013-01-01

    The effects of residual amplitude modulation (RAM) in laser interferometers using heterodyne sensing can be substantial and difficult to mitigate. In this work, we analyze the effects of RAM on a complex laser interferometer used for gravitational wave detection. The RAM introduces unwanted offsets in the cavity length signals and thereby shifts the operating point of the optical cavities from the nominal point via feedback control. This shift causes variations in the sensing matrix, and leads to degradation in the performance of the precision noise subtraction scheme of the multiple-degree-of-freedom control system. In addition, such detuned optical cavities produce an opto-mechanical spring, which also varies the sensing matrix. We use our simulations to derive requirements on RAM for the Advanced LIGO detectors, and show that the RAM expected in Advanced LIGO will not limit its sensitivity.

  2. Reduction of residual amplitude modulation to 1 × 10?? for frequency modulation and laser stabilization.

    Science.gov (United States)

    Zhang, W; Martin, M J; Benko, C; Hall, J L; Ye, J; Hagemann, C; Legero, T; Sterr, U; Riehle, F; Cole, G D; Aspelmeyer, M

    2014-04-01

    Active control and cancellation of residual amplitude modulation (RAM) in phase modulation of an optical carrier is one of the key technologies for achieving the ultimate stability of a laser locked to an ultrastable optical cavity. Furthermore, such techniques are versatile tools in various frequency modulation-based spectroscopy applications. In this Letter we report a simple and robust approach to actively stabilize RAM in an optical phase modulation process. We employ a waveguide-based electro-optic modulator (EOM) to provide phase modulation and implement an active servo with both DC electric field and temperature feedback onto the EOM to cancel both the in-phase and quadrature components of the RAM. This technique allows RAM control on the parts-per-million level where RAM-induced frequency instability is comparable to or lower than the fundamental thermal noise limit of the best available optical cavities. PMID:24686654

  3. [The research on residual amplitude modulation characteristics in fiber frequency modulation spectroscopy].

    Science.gov (United States)

    Fu, Xiao-fang; Zhao, Gang; Ma, Wei-guang; Tan, Wei; Li, Zhi-xin; Dong, Lei; Zhang, Lei; Yin, Wang-bao; Jia, Suo-tang

    2014-06-01

    Frequency modulation spectroscopy (FMS) not only can be used to simultaneously measure the absorption and dispersion of atoms and molecules, but is the key technology of the noise immunity cavity enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). The optical devices or the instability of output light polarization of the laser source will induce the residual amplitude modulation (RAM) in the FMS. RAM greatly limits the FMS technology application in trace gas detection, so the research on the RAM characteristics in the FMS has very important significance. Firstly, the lineshape of FMS without absorption was analyzed, and the impact factors on the RAM were acquired, then the influence of input and output polarization direction and electro-optical modulation (EOM) temperature was measured, respectively. They all have linear relationship with the RAM. The results verify the theoretical analysis and provide the basis for reducing the RAM and other related working. PMID:25358144

  4. Dependence of residual amplitude noise in electro-optic phase modulators on the intensity distribution of the incident field

    International Nuclear Information System (INIS)

    Our results demonstrate that photorefractive residual amplitude modulation (RAM) noise in electro-optic modulators (EOMs) can be reduced by modifying the incident beam intensity distribution. Here we report an order of magnitude reduction in RAM when beams with uniform intensity (flat-top) profiles, generated with an LCOS-SLM, are used instead of the usual fundamental Gaussian mode (TEM00). RAM arises from the photorefractive amplified scatter noise off the defects and impurities within the crystal. A reduction in RAM is observed with increasing intensity uniformity (flatness), which is attributed to a reduction in space charge field on the beam axis. The level of RAM reduction that can be achieved is physically limited by clipping at EOM apertures, with the observed results agreeing well with a simple model. These results are particularly important in applications where the reduction of residual amplitude modulation to 10?6 is essential. (paper)

  5. Analysis of frequency noise in ultra-stable optical oscillators with active control of residual amplitude modulation

    Science.gov (United States)

    Li, Liufeng; Shen, Hui; Bi, Jin; Wang, Chun; Lv, Shasha; Chen, Lisheng

    2014-12-01

    Two 1,064-nm Nd:YAG lasers frequency stabilized by high-finesse optical cavities are developed to investigate various noise mechanisms in ultra-stable optical oscillators. Active control of residual amplitude modulation using a separate sensing path is implemented and its effectiveness in the presence of a resonant optical cavity is theoretically analyzed and experimentally verified by measuring the rejection ratios in optical heterodyne beat between a perturbed laser and a stable reference. Laser frequency noises originated from vibration, residual amplitude modulation, quantum-limited shot noise, and electronic noise are experimentally analyzed. With active control, residual amplitude modulation is suppressed to below 1 × 10-6 at 0.02-1,000 s, reaching a minimum of 2 × 10-7 at ~2 s. A frequency stability of 2 × 10-15 is obtained from 0.1 to 10 s, and the optical heterodyne beat of the two Nd:YAG lasers shows 1-Hz linewidth with a measurement time of 4.096 s. In addition, the experimentally determined linewidths agree well with the calculation according to a simplified relationship between the linewidth and the underlying flicker noise that modulates the laser frequency.

  6. Speech production in amplitude-modulated noise

    DEFF Research Database (Denmark)

    Macdonald, Ewen N; Raufer, Stefan

    2013-01-01

    The Lombard effect refers to the phenomenon where talkers automatically increase their level of speech in a noisy environment. While many studies have characterized how the Lombard effect influences different measures of speech production (e.g., F0, spectral tilt, etc.), few have investigated the consequences of temporally fluctuating noise. In the present study, 20 talkers produced speech in a variety of noise conditions, including both steady-state and amplitude-modulated white noise. While listening to noise over headphones, talkers produced randomly generated five word sentences. Similar to previous studies, talkers raised the level of their voice in steady-state noise. While talkers also increased the level of their voice in amplitude-modulated noise, the increase was not as large as that observed in steady-state noise. Importantly, for the 2 and 4 Hz amplitude-modulated noise conditions, talkers altered the timing of their utterances, reducing the energetic overlap with the masker by approximately 2%. However, for the 1 Hz amplitude-modulated condition, talkers increased the overlap by approximately 4%. Overall, the results demonstrate that talkers are sensitive to the temporal aspects of noisy environments and will alter their speech accordingly.

  7. Amplitude modulation of wind turbine noise

    CERN Document Server

    Makarewicz, Rufin

    2013-01-01

    Due to swish and thump amplitude modulation, the noise of wind turbines cause more annoyance than other environmental noise of the same average level. The wind shear accounts for the thump modulation (van den Berg effect). Making use of the wind speed measurements at the hub height, as well as at the top and the bottom of the rotor disc (Fig.1), the non-standard wind profile is applied. It causes variations in the A-weighted sound pressure level, LpA. The difference between the maximum and minimum of LpA characterizes thump modulation (Fig.2).

  8. Amplitude and phase modulation with waveguide optics

    International Nuclear Information System (INIS)

    We have developed amplitude and phase modulation systems for glass lasers using integrated electro-optic modulators and solid state high-speed electronics. The present and future generation of lasers for Inertial Confinement Fusion require laser beams with complex temporal and phase shaping to compensate for laser gain saturation, mitigate parametric processes such as transverse stimulated Brillouin scattering in optics, and to provide specialized drive to the fusion targets. These functions can be performed using bulk optoelectronic modulators, however using high-speed electronics to drive low voltage integrated optical modulators has many practical advantages. In particular, we utilize microwave GaAs transistors to perform precision, 250 ps resolution temporal shaping. Optical bandwidth is generated using a microwave oscillator at 3 GHz amplified by a solid state amplifier. This drives an integrated electrooptic modulator to achieve laser bandwidths exceeding 30 GHz

  9. Procedure for aligning polarization modulator link for amplitude modulation applications.

    Science.gov (United States)

    Hutchinson, Meredith N; Frigo, Nicholas J; Urick, Vincent J

    2014-10-01

    A procedure is detailed for aligning the transmitted output states of a polarization modulated signal to the analyzer states of a polarizing discriminator in an analog photonic link. The steps in the procedure insure optimal amplitude modulation in the link. Experimental results are presented for biasing in two ways: either the DC bias on the modulator or a rotatable half-wave plate can be used. The corresponding theory is included. PMID:25322059

  10. Amplitude modulation of wind turbine noise

    OpenAIRE

    Makarewicz, Rufin; Golebiewski, Roman

    2013-01-01

    Due to swish and thump amplitude modulation, the noise of wind turbines cause more annoyance than other environmental noise of the same average level. The wind shear accounts for the thump modulation (van den Berg effect). Making use of the wind speed measurements at the hub height, as well as at the top and the bottom of the rotor disc (Fig.1), the non-standard wind profile is applied. It causes variations in the A-weighted sound pressure level, LpA. The difference between ...

  11. Amplitude-modulated fiber-ring laser

    DEFF Research Database (Denmark)

    Caputo, J. G.; Clausen, Carl A. Balslev

    2000-01-01

    Soliton pulses generated by a fiber-ring laser are investigated by numerical simulation and perturbation methods. The mathematical modeling is based on the nonlinear Schrödinger equation with perturbative terms. We show that active mode locking with an amplitude modulator leads to a self-starting of stable solitonic pulses from small random noise, provided the modulation depth is small. The perturbative analysis leads to a nonlinear coupled return map for the amplitude, phase, and position of the soliton pulses circulating in the fiber-ring laser. We established the validity of this approach by comparison with the full numerical simulations. Finally, we discuss possible sources of instability that are due to resonances in the device.

  12. Discrimination of modulation depth of sinusoidal amplitude modulation (SAM) noise.

    Science.gov (United States)

    Wakefield, G H; Viemeister, N F

    1990-09-01

    The detection of sinusoidal amplitude modulation (SAM) provides a lower bound on the degree to which temporal information in the envelope of complex waveforms is encoded by the auditory system. The extent to which changes in the amount of modulation are discriminable provides additional information on the ability of the auditory system to utilize envelope fluctuations. Results from an experiment on the discrimination of modulation depth of broadband noise are presented. Discrimination thresholds, expressed as differences in modulation power, increase monotonically with the modulation depth of the standard, but do not obey Weber's law. The effects of carrier level and of modulation frequency are consistent with those observed in modulation detection: Changes in carrier level have little effect on modulation discrimination; changes in modulation frequency also have little effect except for standards near the modulation detection threshold. The discrimination of modulation depth is consistent with the leaky-integrator model of modulation detection for standards below--10 dB (20 log ms); for standards greater than--10 dB, the leaky integrator predicts better performance than that observed behaviorally. PMID:2229672

  13. Amplitude Modulation Effects in Cardiac Signals

    CERN Document Server

    Peters, Randall; Russell, Michael

    2010-01-01

    A subject's heart beat can be nearly invisible in a spectrum, when that spectrum is generated using conventional methods of Fourier analysis. The phenomenon has been observed in records of both electrocardiography type and seismocardiography type. The mechanisms of nonlinear physics responsible for these complexities involve the phenomenon of amplitude modulation. Fortunately, there is a simple remedy to prevent loss of valuable frequency domain information. Instead of operating on the raw signal, one simply rectifies that signal before performing the fast Fourier transform (FFT) calculation. Alternatively, nearly equivalent spectra can be obtained by operating on the signal with the Teager-Kaiser operator before doing the FFT.

  14. Laryngeal-level amplitude modulation in vibrato.

    Science.gov (United States)

    Dromey, Christopher; Reese, Lorie; Hopkin, J Arden

    2009-03-01

    The goal of this investigation was to test a new methodology for measuring amplitude modulation (AM) at the level of the vocal folds during vibrato in trained singers, because previous research has suggested that AM arises in large part as an acoustic epiphenomenon through an interaction of the harmonics in the laryngeal source with the resonances of the vocal tract as the fundamental frequency oscillates. A within-subjects model was used to compare vocal activity across three pitch and three loudness conditions. Seventeen female singers with a range of training and experience were recorded with a microphone and an electroglottograph (EGG). Fluctuations in the ratio of closing to opening peaks in the first derivative of the EGG signal were used as an index of laryngeal-level AM. Evidence of laryngeal AM was found to a greater or lesser extent in all the singers, and its extent was not related to the degree of training. Across singers and pitch conditions, it was more prominent at lower intensities. The differentiated EGG signal lends itself to the measurement of AM at the level of the larynx, and the extent of the modulation appears more related to the level of vocal effort than to individual singer characteristics. PMID:17658720

  15. CARRIER-FREQUENCY HARMONIZATION STRUCTURE FOR ENHANCED AMPLITUDE MODULATION FUNCTION

    OpenAIRE

    Subba Rao, B. V.; Satyanarayanna, P.

    2013-01-01

    Amplitude Modulation was the major method of influencing sound on a radio signal and is still extensively used in the present days. The characteristic amplitude modulation radio receivers’ automatic gain-control to circumvent bass distortion, generally reacts extreme moreover slowly to average out or overwhelm these intercarrier beat modulations as a result, these extremely aggravating modulation effects are mainly distributed on unbroken to the eavesdropper. A GPS-referenced frequency-sync...

  16. Multilevel phase and amplitude modulation method for holographic memories with programmable phase modulator

    Science.gov (United States)

    Honma, Satoshi; Sekiguchi, Toru

    2014-09-01

    The utilization of spatial quadrature amplitude modulation (SQAM) signals with amplitude and phase modulation is a simple method used to improve storage capacity in a holographic data storage system. We propose a multilevel phase and amplitude modulation method for holographic memories with a programmable phase modulator (PPM). In this method, holographic page data is recorded by a two-step exposure process for different phase-modulated data. There is no need to adjust the positions of spatial light modulators (SLM) with high accuracy because we use only one spatial modulator. We estimate the quality of 16 SQAM signals produced by our technique.

  17. Log-Likelihood Classification Of Quadrature Amplitude Modulation

    Directory of Open Access Journals (Sweden)

    Savita Kamboj

    2013-10-01

    Full Text Available This paper is concerned with amplitude-based log likelihood classification for quadrature amplitude modulation. We derive the amplitude density functions of received QAM signals first, then develop the required statistics for signal classification based on the maximum a posteriori probability criterion and demonstrate a schematic structure of classifier for M-ary QAM signals. It is illustrated successful classification rate reaches 100% for SNR>=15.

  18. Influence of the Amplitude in Lattice Modulation Spectroscopy

    Science.gov (United States)

    Dirks, Andreas; Mikelsons, Karlis; Freericks, Jim; Krishnamurthy, H. R.

    2013-03-01

    Within the Mott-insulating phase of the Hubbard model, linear-response calculations for a periodically modulated optical lattice depth clearly predict a resonance when modulated at a frequency equal to the Hubbard repulsion U. In this work we examine the effect of the amplitude of the lattice depth modulation on the threshold for excitation. Based on a recently developed strong-coupling approach to the non-equilibrium Hubbard model, we report results on the nonlinear regime and discuss effects of the amplitude as compared to the frequency for driving excitations into the upper Hubbard band.

  19. Direct inversion methods for spectral amplitude modulation of femtosecond pulses

    Science.gov (United States)

    Delgado-Aguillón, Jesús; Garduño-Mejía, Jesús; López-Téllez, Juan Manuel; Bruce, Neil C.; Rosete-Aguilar, Martha; Román-Moreno, Carlos Jesús; Ortega-Martínez, Roberto

    2014-04-01

    In the present work, we applied an amplitude-spatial light modulator to shape the spectral amplitude of femtosecond pulses in a single step, without an iterative algorithm, by using an inversion method defined as the generalized retardance function. Additionally, we also present a single step method to shape the intensity profile defined as the influence matrix. Numerical and experimental results are presented for both methods.

  20. Amplitude Modulated Sinusoidal Signal Decomposition for Audio Coding

    DEFF Research Database (Denmark)

    Christensen, M. G.; Jacobson, A.

    2006-01-01

    In this paper, we present a decomposition for sinusoidal coding of audio, based on an amplitude modulation of sinusoids via a linear combination of arbitrary basis vectors. The proposed method, which incorporates a perceptual distortion measure, is based on a relaxation of a nonlinear least-squares minimization. Rate-distortion curves and listening tests show that, compared to a constant-amplitude sinusoidal coder, the proposed decomposition offers perceptually significant improvements in critical transient signals.

  1. Amplitude modulated sinusoidal signal decomposition for audio coding

    DEFF Research Database (Denmark)

    Christensen, Mads GræsbØll; Jakobsson, Andreas

    2006-01-01

    In this letter, we present a decomposition for sinusoidal coding of audio, based on an amplitude modulation of sinusoids via a linear combination of arbitrary basis vectors. The proposed method, which incorporates a perceptual distortion measure, is based on a relaxation of a nonlinear least-squares minimization. Rate-distortion curves and listening tests show that, compared to a constant-amplitude sinusoidal coder, the proposed decomposition offers perceptually significant improvements in critical transient signals.

  2. CARRIER-FREQUENCY HARMONIZATION STRUCTURE FOR ENHANCED AMPLITUDE MODULATION FUNCTION

    Directory of Open Access Journals (Sweden)

    B.V.Subba Rao

    2013-06-01

    Full Text Available Amplitude Modulation was the major method of influencing sound on a radio signal and is still extensively used in the present days. The characteristic amplitude modulation radio receivers’ automatic gain-control to circumvent bass distortion, generally reacts extreme moreover slowly to average out or overwhelm these intercarrier beat modulations as a result, these extremely aggravating modulation effects are mainly distributed on unbroken to the eavesdropper. A GPS-referenced frequency-synchronizer unit could be organized at transmitter sites capable of holding both current and big transmitters as a result basically eradicating carrier beat interference between co-channel amplitude modulation stations. The beat-related properties are a main aspect in the deprivation of dusk and night-time amplitude modulation fringe-area function excellence and the subsequent damage of hearers for effectively all stations. Commonly, an amplitude modulation radio listener for the duration of the sundown and nightfall hours and to a slighter amount in the first day break, obtains undesired sky wave indications from numerous distant locations as well as the desired local signal. The simple oscillator is naturally a predictable high-stability quartz-crystal kind, temperature compensated. To stand long-term drifts, advanced years effects, and loading-circuit variations, the simple oscillator is somewhat adjusted through electronic or mechanical resources to path a high-precision cause of standard frequency. The steady local reference frequency is then used as a timer for a typical numerically applied frequency synthesizer, which is planned to create the speci?c receiver carrier frequency expected.

  3. Residues and filtered D-modules

    OpenAIRE

    Schnell, Christian

    2010-01-01

    For an embedding of sufficiently high degree of a smooth projective variety X into projective space, we use residues to define a filtered holonomic D-module (M, F) on the dual projective space. This gives a concrete description of the intermediate extension to a Hodge module on P of the variation of Hodge structure on the middle-dimensional cohomology of the hyperplane sections of X. We also establish many results about the sheaves F_k M, such as positivity, vanishing theore...

  4. Amplitude Modulation of Atomic Wavefunctions - Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, William E.

    2001-08-01

    This project developed a novel wave function modulation technique. Other modulation techniques use tailored laser pulses to directly excite a time-dependent, modulated wave function from a ground state. Our technique began with one electron already excited to a time independent eigenfunction. Then, by using excitations of a second valence electron, we modulated the other wave function. Our technique had the benefit that it was very efficient, and required low power lasers with no need for precise phase or amplitude control. On the other hand it had the difficulty of being a multi-step laser excitation with a maximum repetition rate of 10 Hz. Over the course of this project, we showed that the technique did work, and work efficiently. However, it was easy to generalize. Since the modulation depended on a difference between electron-electron interactions with the inner electron in a ground or excited state, the efficiency of the modulation was strongly state dependent. For example, we never showed any significant modulation in our tests of barium states, while our strontium measurements did show efficient modulation as long as the state to be modulated was in the 5snd group with n between 30 and 50. We completed some studies of the dependence of the amplitude modulation as we varied the time between the excitation and de-excitation pulses applied to the inner electron. The amplitude of the nearest neighbor states was well described by Multi-Channel Quantum Defect theory, but farther satellites were problematical. This may have simply reflected the low density of measurement points, since the amplitudes of the farther satellites oscillate more quickly with time. As we developed our technique, we showed that we could directly measure autoionization decay rates in the time domain, and that the net effect of a state belonging to a Rydberg series was that exponential decay could not be measured, since any short excitation created a coherent superposition that decayed with significant structure. In addition, we showed that these short-lived states could not be power-broadened in the normal sense. Instead, even at very high power densities, we observed unbroadened, but saturated line shapes. This was a verification of calculations that showed that a when a cosecant-squared pulse shape drives a two level system, that the time and frequency dependencies factor. This means that the entire line shape amplitude varies with pulse power, but that its width and central position are insensitive to driving power.

  5. Focusing Light through Random Photonic Media by Binary Amplitude Modulation

    CERN Document Server

    Akbulut, Duygu; van Putten, Elbert G; Vos, Willem L; Mosk, Allard P

    2011-01-01

    We study the focusing of light through random photonic materials using wavefront shaping. We explore a novel approach namely binary amplitude modulation. To this end, the light incident to a random photonic medium is spatially divided into a number of segments. We identify the segments that give rise to fields that are out of phase with the total field at the intended focus and assign these a zero amplitude, whereas the remaining segments maintain their original amplitude. Using 812 independently controlled segments of light, we find the intensity at the target to be 75 +/- 6 times enhanced over the average intensity behind the sample. We experimentally demonstrate focusing of light through random photonic media using both an amplitude only mode liquid crystal spatial light modulator and a MEMS-based spatial light modulator. Our use of Micro Electro-Mechanical System (MEMS)-based digital micromirror devices for the control of the incident light field opens an avenue to high speed implementations of wavefront ...

  6. Conceptual design of dispersion interferometer using ratio of modulation amplitudes

    International Nuclear Information System (INIS)

    Since a dispersion interferometer is free from mechanical vibrations, it does not need a vibration compensation system even if a wavelength of a probe beam is short (e.x. infrared and near infrared region). This paper describes a new signal processing of the dispersion interferometer using a ratio of modulation amplitudes with a photoelastic modulator. The proposed method is immune to changes in detected signal intensities and the signal processing system becomes simple. Designs of the optical system of the dispersion interferometer for proof of principle, especially specification of a nonlinear optical crystal, are also shown. (author)

  7. Multi-hit time-to-amplitude CAMAC module (MTAC)

    International Nuclear Information System (INIS)

    A Multi-Hit Time-to-Amplitude Module (MTAC) for the SLAC Mark III drift chamber system has been designed to measure drift time by converting time-proportional chamber signals into analog levels, and converting the analog data by slow readout via a semi-autonomous controller in a CAMAC crate. The single width CAMAC module has 16 wire channels, each with a 4-hit capacity. An externally generated common start initiates an internal precision ramp voltage which is then sampled using a novel shift register gating scheme and CMOS sampling switches. The detailed design and performance specifications are described

  8. Coherent amplitude modulation of electron-beam-driven Langmuir waves

    Directory of Open Access Journals (Sweden)

    K. Baumgärtel

    2013-04-01

    Full Text Available A linear approach to the phenomenon of irregular amplitude modulation of beam-driven Langmuir waves, developed in a previous paper, is extended to explain periodic modulation as well. It comes about by beating of the fastest growing mode of the instability with beam-aligned plasma oscillations. They are naturally generated in a uniform domain of beam–plasma interaction prior to the onset of the instability. Particle-in-cell (PIC simulations support the results of the linear analysis.

  9. Amplitude modulation control of escape from a potential well

    Energy Technology Data Exchange (ETDEWEB)

    Chacón, R. [Departamento de Física Aplicada, Escuela de Ingenierías Industriales, Universidad de Extremadura, Apartado Postal 382, E-06006 Badajoz (Spain); Martínez García-Hoz, A. [Departamento de Física Aplicada, Escuela Universitaria Politécnica, Universidad de Castilla-La Mancha, E-13400 Almadén (Ciudad Real) (Spain); Miralles, J.J. [Departamento de Física Aplicada, Escuela de Ingenieros Industriales, Universidad de Castilla-La Mancha, E-02071 Albacete (Spain); Martínez, P.J. [Departamento de Física Aplicada, E.I.N.A., Universidad de Zaragoza, E-50018 Zaragoza (Spain); Instituto de Ciencia de Materiales de Aragón, CSIC – Universidad de Zaragoza, E-50009 Zaragoza (Spain)

    2014-03-01

    We demonstrate the effectiveness of periodic amplitude modulations in controlling (suppressing and enhancing) escape from a potential well through the universal model of a damped Helmholtz oscillator subjected to an external periodic excitation (the escape-inducing excitation) whose amplitude is periodically modulated (the escape-controlling excitation). Analytical and numerical results show that this multiplicative control works reliably for different subharmonic resonances between the two periodic excitations involved, and that its effectiveness is comparable to those of different methods of additive control. Additionally, we demonstrate the robustness of the multiplicative control against the presence of low-intensity Gaussian noise. -- Highlights: •Multiplicative control of escape from a potential well has been demonstrated. •Theoretical predictions are obtained from a Melnikov analysis. •It has been shown the robustness of the multiplicative control against noise.

  10. Amplitude modulation control of escape from a potential well

    International Nuclear Information System (INIS)

    We demonstrate the effectiveness of periodic amplitude modulations in controlling (suppressing and enhancing) escape from a potential well through the universal model of a damped Helmholtz oscillator subjected to an external periodic excitation (the escape-inducing excitation) whose amplitude is periodically modulated (the escape-controlling excitation). Analytical and numerical results show that this multiplicative control works reliably for different subharmonic resonances between the two periodic excitations involved, and that its effectiveness is comparable to those of different methods of additive control. Additionally, we demonstrate the robustness of the multiplicative control against the presence of low-intensity Gaussian noise. -- Highlights: •Multiplicative control of escape from a potential well has been demonstrated. •Theoretical predictions are obtained from a Melnikov analysis. •It has been shown the robustness of the multiplicative control against noise.

  11. Amplitude modulation reflectometry for density profile and fluctuations studies

    International Nuclear Information System (INIS)

    One of the main problems which arises in density profile measurements by reflectometry is the need for continuous tracking of the phase delay: fast density fluctuations and strong modulation on the amplitude of the reflected signal usually bring to 'fringe jumps' in the phase signal. Amplitude Modulation Reflectometry performs a time delay measurement by the determination of the phase delay of the modulating envelope of a millimeter wave reflected by the plasma. The phase delays involved are small, the measurement is not affected by the fluctuations and can be directly performed without complicated fringe counters: the method provides a promising possibility for real time determination of the plasma position and density profile. In the present paper the principles of the method are presented as well as the analysis on the effects of phase and amplitude fluctuations, dispersive effects and accuracy requirements. The application to the future JET Divertor plasmas will be also presented together with an initial design of the system. (author). 3 refs, 2 figs

  12. Amplitude modulation of atomic wave functions. Final report

    International Nuclear Information System (INIS)

    The major theoretical advance has been to show that one can modulate Rydberg wave functions using either of two methods: (1) the amplitude modulation technique which depends on autoionization to deplete part of the wave function, or (2) a phase modulation method, which uses a change in the core potential to create a localized phase shift in the wave function. Essentially, these two methods can both be seen as using the core potential to change the Rydberg wave function, using the imaginary part of the potential to do amplitude modulation, or using the real part of the potential to do phase modulation. This work will be published as the authors acquire experimental results which show the differences between the two methods. One of the results of this theoretical study is that the initial proposal to study Barium 6snd states had a significant flaw. Neither the autoionization time, nor the quantum defect shifts are very large in these cases. This means that the modulation is relatively small. This shows itself primarily in the difficulty of seeing significant population redistribution into different 6snd states. The authors intend to correct this in the next funding cycle either: (a) by using the more quickly decaying Ba 6pnf states to modulate 6snd states, or (b) by using Sr 5 snd states, as outlined in this report. Their first, low power experiments are complete. These experiments have used two pulses to do a temporal version of the Ramsey separated oscillatory fields excitation. The two pulses are generated by passing the single pulse through a Michelson-Morley interferometer, which is computer controlled to sweep one arm through 2.5 microm in steps of 10 nm. The second pulse's excitation interferes with that of the first pulse, and so the total excitation has a sinusoidal variation (with a time period equal to the optical period) on top of a constant background. The amplitude of the total variation should decay at half of the rate decay rate of the autoionizing state, so this produces a time-resolved measurement of the very rapid autoionization decay. Although this does not yet show that the atom stores modulations in the bound coherent state, it does demonstrate that the atom can be excited to an autoionizing state with high efficiency, and then brought back to a bound state at a later time. The second set of experiments takes the previous work to the strong coupling regime

  13. Spatial release from masking for amplitude modulated and non-modulated noise stimuli

    Science.gov (United States)

    Kop?o, Norbert; Shinn-Cunningham, Barbara G.

    2005-04-01

    The ability to hear a target sound (T) masked by another sound (M) improves when the T and M are spatially separated, a phenomenon known as spatial release from masking (SRM). Target detectability is also influenced by temporal characteristics of T and M (e.g., by the presence or absence of amplitude modulation). The current study examines how SRM is influenced by amplitude modulation. Detection thresholds were measured for a broadband noise target (T) temporally and spectrally centered within a broadband noise masker (M). Thresholds were measured for all combinations of five spatial configurations of T and M and five modulation conditions (all combinations of T and M modulated and unmodulated; when both T and M were modulated, the modulation could either be equal or pi out of phase). In all cases, the amplitude modulation, if present, had a rate of 40 Hz and depth of 0.5. Modulation had a complex effect on detection threshold. Thresholds improved by as much as 6 dB (relative to the no-modulation control) in some spatial configurations, but were nearly unaffected in others. These results have important implications for understanding the processes involved in the perception of simultaneous complex signals. [Work supported by NSF and NAS.

  14. Masking of speech by amplitude-modulated noise

    Science.gov (United States)

    Arlinger, S.; Gustafsson, H.-Å.

    1991-12-01

    The degree of masking of human speech by environmental noise may be influenced by amplitude variations in the noise. The listener's condition with respect to age and auditory function may affect his sensitivity to such noise. Also, fatigue effects are possible after prolonged exposure to masking noise. These aspects have been tested in the present study. The results show that in general, amplitude modulation of a masking noise reduces its speech masking effect as compared to unmodulated noise of the same r.m.s. sound level and spectrum. Age did not affect the release of masking found in AM noise. However, hearing-impaired listeners obtained much less release of speech masking than those with normal hearing. Small but statistically significant fatigue effects were found after up to 60 min exposure to noise at 60 dB SPL. The speech-to-noise ratio needed for 30% correct speech recognition was significantly affected by both age and hearing loss.

  15. Dispersion interferometer using modulation amplitudes on LHD (invited)

    International Nuclear Information System (INIS)

    Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 1017 m?3 is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 1020 m?3 can be overcome by a sufficient sampling rate of about 100 kHz

  16. Dispersion interferometer using modulation amplitudes on LHD (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Akiyama, T., E-mail: takiyama@lhd.nifs.ac.jp; Yasuhara, R.; Kawahata, K. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292 (Japan); Okajima, S.; Nakayama, K. [Chubu University, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan)

    2014-11-15

    Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup ?3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup ?3} can be overcome by a sufficient sampling rate of about 100 kHz.

  17. Phase-visibility modulating interferometry by binary non-quadrature amplitude modulation with neutral density filters

    Science.gov (United States)

    Rivera-Ortega, Uriel; Meneses-Fabian, Cruz; Rodriguez-Zurita, Gustavo; Robledo-Sanchez, Carlos

    2014-04-01

    An alternative method for phase retrieval based on spatial and binary non-quadrature amplitude modulation (NQAM) is presented. This proposal is based on the superposition of a probe beam with a reference beam modulated in phase and amplitude (PAM) by NQAM, which is implemented by two neutral density filters (NDF) in a three-beam Mach-Zehnder interferometer (MZI). The principal advantage of this proposal lies in an analytical relationship between the variations of phase and visibility in an interferogram with the variations in the amplitudes of the reference beams used to implement NQAM; thus, the interferograms can be normalized and their introduced phase variations can be known from the measured intensities. Consequently it is possible to successfully retrieve the object phase. It is worthy to note that this method is capable of accepting that the phase and visibility variations in the interferograms could be spatial functions.

  18. External and internal limitations in amplitude-modulation processing

    DEFF Research Database (Denmark)

    Ewert, Stephan; Dau, Torsten

    2004-01-01

    Three experiments are presented to explore the relative role of "external" signal variability and "internal" resolution limitations of the auditory system in the detection and discrimination of amplitude modulations (AM). In the first experiment, AM-depth discrimination performance was determined using sinusoidally modulated broadband-noise and pure-tone carriers. The AM index, m, of the standard ranged from -28 to -3 dB (expressed as 20 log m). AM-depth discrimination thresholds were found to be a fraction of the AM depth of the standard for standards down to -18 dB, in the case of the pure-tone carrier, and down to -8 dB, in the case of the broadband-noise carrier. For smaller standards, AM-depth discrimination required a fixed increase in AM depth, independent of the AM depth of the standard. In the second experiment, AM-detection thresholds were obtained for signal-modulation frequencies of 4, 16, 64, and 256 Hz, applied to either a band-limited random-noise carrier or a deterministic ("frozen") noise carrier, as a function of carrier bandwidth (8 to 2048 Hz). In general, detection thresholds were higher for the random- than for the frozen-noise carriers. For both carrier types, thresholds followed the pattern expected from frequency-selective processing of the stimulus envelope. The third experiment investigated AM masking at 4, 16, and 64 Hz in the presence of a narrow-band masker modulation. The variability of the masker was changed from entirely frozen to entirely random, while the long-term average envelope power spectrum was held constant. The experiment examined the validity of a long-term average quantity as the decision variable, and the role of memory in experiments with frozen-noise maskers. The empirical results were compared to predictions obtained with two modulation-filterbank models. The predictions revealed that AM-depth discrimination and AM detection are limited by a combination of the external signal variability and an internal "Weber-fraction" noise process.

  19. Characterization and Compensation of the Residual Chirp in a Mach-Zehnder-Type Electro-Optical Intensity Modulator

    OpenAIRE

    Rogers Iii, C. E.; Carini, J. L.; Pechkis, J. A.; Gould, P. L.

    2009-01-01

    We utilize various techniques to characterize the residual phase modulation of a fiber-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the n...

  20. nipi delta-doping superlattices for amplitude modulation

    Scientific Electronic Library Online (English)

    C. V.-B., Tribuzy; S. M., Landi; M. P., Pires; R., Butendeich; P. L., Souza; A. C., Bittencourt; G. E., Marques; A. B., Henriques.

    2002-06-01

    Full Text Available SciELO Brazil | Language: English Abstract in english GaAs/AlGaAs multiple quantum well structures containing an nipi delta-doping superlattice, where the n-type doping is inserted in the quantum wells and the p-type in the barriers, have been studied in detail to evaluate their potential for use in the fabrication of amplitude modulators. It is shown [...] that C is an adequate p-type dopant for such structures, however, little exibility is found in the growth conditions, in particular for the V to III uxes ratio, for obtaining such layers. It is also observed that the required balance between n and p type doping levels is not trivial to be achieved due to the presence of interface hole traps whose population depends on the quantum well doping concentration. In addition, the observed photoluminescence near-edge emission at room temperature occurs at essentially the same energy as that of an equivalent undoped structure. Finally, no deep level emissions are observed which could deteriorate the device performance.

  1. Removal of residual nuclei following a cavitation event using low-amplitude ultrasound.

    Science.gov (United States)

    Duryea, Alexander P; Cain, Charles A; Tamaddoni, Hedieh A; Roberts, William W; Hall, Timothy L

    2014-10-01

    Microscopic residual bubble nuclei can persist on the order of 1 s following a cavitation event. These bubbles can limit the efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy, because they attenuate pulses that arrive subsequent to their formation and seed repetitive cavitation activity at a discrete set of sites (cavitation memory). Here, we explore a strategy for the removal of these residual bubbles following a cavitation event, using low-amplitude ultrasound pulses to stimulate bubble coalescence. All experiments were conducted in degassed water and monitored using high-speed photography. In each case, a 2-MHz histotripsy transducer was used to initiate cavitation activity (a cavitational bubble cloud), the collapse of which generated a population of residual bubble nuclei. This residual nuclei population was then sonicated using a 1 ms pulse from a separate 500-kHz transducer, which we term the bubble removal pulse. Bubble removal pulse amplitudes ranging from 0 to 1.7 MPa were tested, and the backlit area of shadow from bubbles remaining in the field following bubble removal was calculated to quantify efficacy. It was found that an ideal amplitude range exists (roughly 180 to 570 kPa) in which bubble removal pulses stimulate the aggregation and subsequent coalescence of residual bubble nuclei, effectively removing them from the field. Further optimization of bubble removal pulse sequences stands to provide an adjunct to cavitation-based ultrasound therapies such as shock wave lithotripsy and histotripsy, mitigating the effects of residual bubble nuclei that currently limit their efficacy. PMID:25265172

  2. Residual fatigue life estimation using a nonlinear ultrasound modulation method

    Science.gov (United States)

    Piero Malfense Fierro, Gian; Meo, Michele

    2015-02-01

    Predicting the residual fatigue life of a material is not a simple task and requires the development and association of many variables that as standalone tasks can be difficult to determine. This work develops a modulated nonlinear elastic wave spectroscopy method for the evaluation of a metallic components residual fatigue life. An aluminium specimen (AA6082-T6) was tested at predetermined fatigue stages throughout its fatigue life using a dual-frequency ultrasound method. A modulated nonlinear parameter was derived, which described the relationship between the generation of modulated (sideband) responses of a dual frequency signal and the linear response. The sideband generation from the dual frequency (two signal output system) was shown to increase as the residual fatigue life decreased, and as a standalone measurement method it can be used to show an increase in a materials damage. A baseline-free method was developed by linking a theoretical model, obtained by combining the Paris law and the Nazarov–Sutin crack equation, to experimental nonlinear modulation measurements. The results showed good correlation between the derived theoretical model and the modulated nonlinear parameter, allowing for baseline-free material residual fatigue life estimation. Advantages and disadvantages of these methods are discussed, as well as presenting further methods that would lead to increased accuracy of residual fatigue life detection.

  3. Observations on auditory learning in amplitude- and frequency-modulation rate discrimination

    DEFF Research Database (Denmark)

    Hoffmann, Pablo F.

    2010-01-01

    Because amplitude- and frequency-modulated sounds can be the basis for the synthesis of many complex sounds, they can be good candidates in the design of training systems aiming at improving the acquisition of perceptual skills that can benefit from information provided via the auditory channel. One of the key issues when designing such training systems is in the assessment of transfer of learning. In this study we present data on the learning of an auditory task involving sinusoidal amplitude- and frequency-modulated tones. Modulation rate discrimination thresholds were measured during pre-training, training, a post-training stages. During training, listeners were divided into two groups; one group trained on amplitude-modulation rate discrimination and the other group trained on frequency-modulation rate discrimination. Results will be discussed in terms of their implications for training applications by addressing the transfer of learning across carrier frequency, modulation rate, and modulation type.

  4. Effects of amplitude modulation on nonlinear interactions between electrons and chorus waves

    Science.gov (United States)

    Tao, X.; Bortnik, J.; Thorne, R. M.; Albert, J. M.; Li, W.

    2012-03-01

    The effects of amplitude modulation on nonlinear interactions between a parallel propagating chorus wave packet and electrons in a dipole field are investigated in this work using a test particle code. Previous research used a single wave to model a chorus wave element, leading to nonlinear processes such as phase trapping and bunching when the wave amplitude was large enough. However, high resolution observations of chorus wave packets show a modulation of the wave amplitude, forming the so-called chorus subpackets or subelements. Here we first extend a previous method to model a realistic chorus packet. Using the modeled chorus packet, we demonstrate directly that including the realistic amplitude modulation could significantly affect the behavior of resonant electrons. Our results suggest that the amplitude modulation should be considered in the quantitative treatment of interactions between electrons and chorus waves.

  5. Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation.

    Science.gov (United States)

    Huang, Y P; Wang, J S; Huang, K N; Ho, C T; Huang, J D; Young, M S

    2007-06-01

    A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the "measurement pulse" in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation. PMID:17614634

  6. Characterization and Compensation of the Residual Chirp in a Mach-Zehnder-Type Electro-Optical Intensity Modulator

    CERN Document Server

    Rogers, C E; Pechkis, J A; Gould, P L

    2009-01-01

    We utilize various techniques to characterize the residual phase modulation of a fiber-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement.

  7. Detection of sinusoidal amplitude modulation in logarithmic frequency sweeps across wide regions of the spectrum

    OpenAIRE

    Hsieh, I-hui; Saberi, Kourosh

    2010-01-01

    Many natural sounds such as speech contain concurrent amplitude and frequency modulation (AM and FM), with the FM components often in the form of directional frequency sweeps or glides. Most studies of modulation coding, however, have employed one modulation type in stationary carriers, and in cases where mixed-modulation sounds have been used, the FM component has typically been confined to an extremely narrow range within a critical band. The current study examined the ability to detect AM ...

  8. Analyses of the mechanisms of amplitude modulation of aero-acoustic wind turbine sound

    DEFF Research Database (Denmark)

    Fischer, Andreas; Aagaard Madsen, Helge

    2014-01-01

    This paper explores the source mechanism which cause amplitude modulation of the emitted sound of a wind turbine at large distances from the turbine, named as other amplitude modulation. Measurements of the fluctuating surface pressure on a 2.3MW wind turbine showed a considerable variation over a blade revolution in the presence of angle of attack variations. If the blade undergoes transient stall, the variation of the surface pressure spectrum was enhanced and shifted to frequencies below 200Hz. The surface pressure spectra could be directly related to the emitted far eld sound. These ndings give further evidence that transient stall is a main mechanism to cause other amplitude modulation. Wind shear was identified as a critical condition to cause angle of attack variations. Dierent control strategies to mitigate other amplitude modulation were proposed.

  9. Characterizing Alzheimer’s Disease Severity via Resting-Awake EEG Amplitude Modulation Analysis

    OpenAIRE

    Fraga, Francisco J.; Falk, Tiago H.; Kanda, Paulo A. M.; Anghinah, Renato

    2013-01-01

    Changes in electroencephalography (EEG) amplitude modulations have recently been linked with early-stage Alzheimer’s disease (AD). Existing tools available to perform such analysis (e.g., detrended fluctuation analysis), however, provide limited gains in discriminability power over traditional spectral based EEG analysis. In this paper, we explore the use of an innovative EEG amplitude modulation analysis technique based on spectro-temporal signal processing. More specifically, full-band EE...

  10. Charged-particle scattering in the presence of an amplitude-modulated laser field

    International Nuclear Information System (INIS)

    The differential cross section (DCS) of charged-particle scattering by a static potential in teh presence of an amplitude-modulated radiation field is derived. The first Born approximation, a modulation frequency much less than the carrier frequency and modulation depths smaller than unity are used. Through an amplification factor the calculated DCS with n-photon exchanges are compared with those calculated for a homogeneous, single-mode radiation field. In general, the modulation of the amplitude is found to give rise to a significant averaging of the DCS with different numbers of exchanged photons, especially when the modulation depth is not too small. For relatively large modulation depths the results obtained show some features also common to chaotic fields. For modulation depths near unity a strong temporal inhomogeneity mechanism comes into play, enhancing DCS with no photon exchanges and levelling those with n is not equal to O. (author)

  11. Origin of a sensitive dependence of calculated ??-decay amplitudes on the particle-particle residual interaction

    Science.gov (United States)

    Rodin, Vadim; Faessler, Amand

    2011-07-01

    In the present work the sensitivity of calculated ??-decay amplitudes to a realistic residual interaction is analyzed in the framework of the approach of O. A. Rumyantsev and M. H. Urin, Phys. Lett. BPYLBAJ0370-269310.1016/S0370-2693(98)01291-X 443, 51 (1998). and V. A. Rodin, M. H. Urin, and A. Faessler, Nucl. Phys. ANUPABL0375-947410.1016/j.nuclphysa.2004.10.010 747, 297 (2005). Both the Gamow-Teller (GT) and Fermi (F) matrix elements M2? for two-neutrino ?? decay (2??? decay), along with the monopole transition contributions to the total matrix elements M0? of neutrinoless ?? decay (0??? decay), are calculated within the quasiparticle random-phase approximation (QRPA). In the aforementioned approach decompositions of M2? and M0? can be obtained in terms of the corresponding energy-weighted sum rules S. It is shown that in most of the cases almost the whole dependence of M2? and M0? on the particle-particle (p-p) renormalization parameter gpp is accounted for by the gpp dependence of the corresponding sum rules S. General expressions relating S to a realistic residual particle-particle interaction are derived, which show a pronounced sensitivity of S to the singlet-channel interaction in the case of F transitions and to the triplet-channel interaction in the case of GT transitions. Thus, the sensitivity of M2? and M0? to the SU(4)-symmetry-breaking part of the p-p residual interaction is dictated by the generic structure of the ??-decay amplitudes. Therefore, a choice of this part in a particular calculation needs a special caution. Finally, a better isospin-consistent way of renormalization of a realistic residual p-p interaction to use in QRPA calculations is suggested.

  12. Novel optical pulse characterization technique using sinusoidal optical phase modulation with a broad usable modulation amplitude range

    OpenAIRE

    Donegan, John Francis

    2009-01-01

    Advanced optical pulse characterization methods are essential for high-speed optical communications. Recently non-iterative characterization of general optical pulses using sinusoidal optical phase modulation has been reported [1-2]. However, the usable phase modulation amplitude with this method has a relatively small upper limit (0.88 radians [1]). In this paper we propose a novel non-iterative optical pulse characterization technique using sinusoidal optical phase modulation, w...

  13. A linear model for amplitude modulation of Langmuir waves in weak electron-beam plasma interaction

    Directory of Open Access Journals (Sweden)

    K. Baumgärtel

    2013-01-01

    Full Text Available A simple linear approach to the phenomenon of amplitude modulation of Langmuir waves in weak beam plasma interaction is presented. During the short growth phase of the instability and within the longer period after saturation, the waves are described by their linear kinetic dispersion properties.The amplitude modulation appears as result of the beating of waves with different wavelengths and amplitudes that have grown from noise in the initial phase. The Langmuir wave fields are calculated via FFT (fast Fourier transform technique. The resulting waveforms in temporal representation are quite similar to those observed by spacecraft.

  14. An amplitude modulated laser system for distance and displacement measurement

    Science.gov (United States)

    Rogowski, Robert S.; Heyman, Joseph S.; Holben, Milford S., Jr.

    1986-01-01

    A laser distance and displacement measurement system is being developed to monitor small displacements in large space structures for strain analysis and structural control. The reflected laser beam is focused on a detector and the detected signal is mixed with the reference. Small displacements are indicated by a change in modulation frequency which is adjusted to maintain quadrature between the received signal and the reference signal from the voltage-controlled oscillator in a phase-locked loop. Measurement of absolute distance is accomplished by sweeping the modulation frequency from a quadrature lock point to an adjacent lock point.

  15. Diffusion-induced periodic transition between oscillatory modes in amplitude-modulated patterns

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Xiaodong; He, Yuxiu; Wang, Shaorong; Gao, Qingyu, E-mail: gaoqy@cumt.edu.cn [College of Chemical Engineering, China University of Mining and Technology, Xuzhou 221008 (China); Epstein, Irving R., E-mail: epstein@brandeis.edu [Department of Chemistry and Volen Center for Complex Systems, MS 015, Brandeis University, Waltham, Massachusetts 02454-9110 (United States); Wang, Qun [School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116 (China)

    2014-06-15

    We study amplitude-modulated waves, e.g., wave packets in one dimension, overtarget spirals and superspirals in two dimensions, under mixed-mode oscillatory conditions in a three-variable reaction-diffusion model. New transition zones, not seen in the homogeneous system, are found, in which periodic transitions occur between local 1{sup N?1} and 1{sup N} oscillations. Amplitude-modulated complex patterns result from periodic transition between (N???1)-armed and N-armed waves. Spatial recurrence rates provide a useful guide to the stability of these modulated patterns.

  16. A novel amplitude modulated triangular carrier gain linearization technique for SPWM inverter

    OpenAIRE

    Ramkumar Subburam; Jeevananthan Seenithangam; Kamaraj Vijayarajan

    2009-01-01

    This paper presents a new method to extend the linearity of the sinusoidal pulse width modulation (SPWM) to full range of the pulse dropping region. The proposed amplitude modulated triangular carrier PWM method (AMTCPWM) increases the dynamic range of the SPWM control and eliminates the need of nonlinear modulation in the pulse dropping region to reach the square wave boundary. The novel method combines the spectral quality of SPWM with the efficient single-mode linear control. A simple anal...

  17. Tunable Pulse Amplitude and Position Modulation Technique for Reliable Optical Wireless Communication Channels

    OpenAIRE

    Leeson, Mark S.; Shaobo Sun; Green, Roger J.; Yu Zeng

    2007-01-01

    Modulation techniques have attracted increasing attention in optical wireless communications. Basic schemes such as on off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM) have been validated as suitable for the optical wireless channel. This paper starts from the analysis of...

  18. Extending single molecule fluorescence observation time by amplitude-modulated excitation

    International Nuclear Information System (INIS)

    We present a hardware-based method that can improve single molecule fluorophore observation time by up to 1500% and super-localization by 47% for the experimental conditions used. The excitation was modulated using an acousto-optic modulator (AOM) synchronized to the data acquisition and inherent data conversion time of the detector. The observation time and precision in super-localization of four commonly used fluorophores were compared under modulated and traditional continuous excitation, including direct total internal reflectance excitation of Alexa 555 and Cy3, non-radiative Förster resonance energy transfer (FRET) excited Cy5, and direct epi-fluorescence wide field excitation of Rhodamine 6G. The proposed amplitude-modulated excitation does not perturb the chemical makeup of the system or sacrifice signal and is compatible with multiple types of fluorophores. Amplitude-modulated excitation has practical applications for any fluorescent study utilizing an instrumental setup with time-delayed detectors. (technical note)

  19. Amplitude modulation depth discrimination of a sinusoidal carrier: Effect of stimulus durationa)

    OpenAIRE

    Lee, Jungmee; Bacon, Sid P.

    1997-01-01

    Discrimination of the change in depth of sinusoidal amplitude modulation (AM) was investigated as a function of stimulus duration. The carrier frequency was 4000 Hz, the standard modulation depth (m) was either 0.1, 0.18, or 0.3, and the modulation rate was either 10, 20, 40, or 80 Hz. For all standard depths and modulation rates, threshold (?m) decreased by more than a factor of two as stimulus duration doubled from the shortest duration used up to a certain duration (critical duration), be...

  20. A perturbative analysis of modulated amplitude waves in Bose-Einstein condensates

    International Nuclear Information System (INIS)

    We apply Lindstedt's method and multiple scale perturbation theory to analyze spatio-temporal structures in nonlinear Schroedinger equations and thereby study the dynamics of quasi-one-dimensional Bose-Einstein condensates with mean-field interactions. We determine the dependence of the amplitude of modulated amplitude waves on their wave number. We also explore the band structure of Bose-Einstein condensates in detail using Hamiltonian perturbation theory and supporting numerical simulations

  1. Characterizing Alzheimer's disease severity via resting-awake EEG amplitude modulation analysis.

    Science.gov (United States)

    Fraga, Francisco J; Falk, Tiago H; Kanda, Paulo A M; Anghinah, Renato

    2013-01-01

    Changes in electroencephalography (EEG) amplitude modulations have recently been linked with early-stage Alzheimer's disease (AD). Existing tools available to perform such analysis (e.g., detrended fluctuation analysis), however, provide limited gains in discriminability power over traditional spectral based EEG analysis. In this paper, we explore the use of an innovative EEG amplitude modulation analysis technique based on spectro-temporal signal processing. More specifically, full-band EEG signals are first decomposed into the five well-known frequency bands and the envelopes are then extracted via a Hilbert transform. Each of the five envelopes are further decomposed into four so-called modulation bands, which were chosen to coincide with the delta, theta, alpha and beta frequency bands. Experiments on a resting-awake EEG dataset collected from 76 participants (27 healthy controls, 27 diagnosed with mild-AD, and 22 with moderate-AD) showed significant differences in amplitude modulations between the three groups. Most notably, i) delta modulation of the beta frequency band disappeared with an increase in disease severity (from mild to moderate AD), ii) delta modulation of the theta band appeared with an increase in severity, and iii) delta modulation of the beta frequency band showed to be a reliable discriminant feature between healthy controls and mild-AD patients. Taken together, it is hoped that the developed tool can be used to assist clinicians not only with early detection of Alzheimer's disease, but also to monitor its progression. PMID:24015222

  2. Characterizing Alzheimer’s Disease Severity via Resting-Awake EEG Amplitude Modulation Analysis

    Science.gov (United States)

    Fraga, Francisco J.; Falk, Tiago H.; Kanda, Paulo A. M.; Anghinah, Renato

    2013-01-01

    Changes in electroencephalography (EEG) amplitude modulations have recently been linked with early-stage Alzheimer’s disease (AD). Existing tools available to perform such analysis (e.g., detrended fluctuation analysis), however, provide limited gains in discriminability power over traditional spectral based EEG analysis. In this paper, we explore the use of an innovative EEG amplitude modulation analysis technique based on spectro-temporal signal processing. More specifically, full-band EEG signals are first decomposed into the five well-known frequency bands and the envelopes are then extracted via a Hilbert transform. Each of the five envelopes are further decomposed into four so-called modulation bands, which were chosen to coincide with the delta, theta, alpha and beta frequency bands. Experiments on a resting-awake EEG dataset collected from 76 participants (27 healthy controls, 27 diagnosed with mild-AD, and 22 with moderate-AD) showed significant differences in amplitude modulations between the three groups. Most notably, i) delta modulation of the beta frequency band disappeared with an increase in disease severity (from mild to moderate AD), ii) delta modulation of the theta band appeared with an increase in severity, and iii) delta modulation of the beta frequency band showed to be a reliable discriminant feature between healthy controls and mild-AD patients. Taken together, it is hoped that the developed tool can be used to assist clinicians not only with early detection of Alzheimer’s disease, but also to monitor its progression. PMID:24015222

  3. Amplitude modulation theory and its application to two-mode buckling problems

    Energy Technology Data Exchange (ETDEWEB)

    Hui, D.

    1985-11-01

    This paper aims to review Koiter's theory of amplitude modulation of the local mode and present it in a form suitable for general application. Various features of the theory are compared with Koiter's general theory of 1945. The amplitude modulation theory is applied to two-mode buckling of stringer stiffened cylindrical shells under axial compression. New mode interaction results are reported involving the simultaneous local and overall buckling in which the local mode is postbuckling unstable. (orig.).

  4. Pulsational Frequency and Amplitude Modulation in the $\\delta$\\,Sct star KIC\\,7106205

    CERN Document Server

    Bowman, Dominic M

    2014-01-01

    Analysis of the \\textit{Kepler} $\\delta$\\,Sct star KIC\\,7106205 showed amplitude modulation in a single pressure mode, whilst all other pressure and gravity modes remained stable in amplitude and phase over the 1470\\,d length of the dataset. The \\textit{Kepler} dataset was divided into a series with time bins of equal length for which consecutive Fourier transforms were calculated. An optimum fixed frequency, calculated from a least-squares fit of all data, allowed amplitude and phase of each pulsation mode for each time bin to be tracked. The single pressure mode at $\

  5. Amplitude and frequency modulation torsional resonance mode atomic force microscopy of a mineral surface.

    Science.gov (United States)

    Yurtsever, Ayhan; Gigler, Alexander M; Stark, Robert W

    2009-02-01

    Scanning probe imaging in a shear force mode allows for the characterization of in-plane surface properties. In a standard AFM, shear force imaging can be realized by the torsional resonance mode. In order to investigate the imaging conditions on mineral surfaces, a torsional resonance mode atomic force microscope was operated in amplitude (AM) and frequency modulation (FM) feedback. Freshly cleaved chlorite was investigated, which showed brucite-like and talc-like surface areas. In constant amplitude FM mode, a slight variation in energy dissipation was observed between both surfaces. Amplitude and frequency vs. distance curves revealed that the tip was in repulsive contact with the specimen during imaging. PMID:19131169

  6. Amplitude and frequency modulation torsional resonance mode atomic force microscopy of a mineral surface

    Energy Technology Data Exchange (ETDEWEB)

    Yurtsever, Ayhan; Gigler, Alexander M. [Department of Earth and Environmental Sciences and Center for NanoScience, Ludwig-Maximilians-Universitaet Muenchen, Theresienstr. 41, 80333 Munich (Germany); Stark, Robert W. [Department of Earth and Environmental Sciences and Center for NanoScience, Ludwig-Maximilians-Universitaet Muenchen, Theresienstr. 41, 80333 Munich (Germany)], E-mail: stark@lrz.uni-muenchen.de

    2009-02-15

    Scanning probe imaging in a shear force mode allows for the characterization of in-plane surface properties. In a standard AFM, shear force imaging can be realized by the torsional resonance mode. In order to investigate the imaging conditions on mineral surfaces, a torsional resonance mode atomic force microscope was operated in amplitude (AM) and frequency modulation (FM) feedback. Freshly cleaved chlorite was investigated, which showed brucite-like and talc-like surface areas. In constant amplitude FM mode, a slight variation in energy dissipation was observed between both surfaces. Amplitude and frequency vs. distance curves revealed that the tip was in repulsive contact with the specimen during imaging.

  7. Amplitude and frequency modulation torsional resonance mode atomic force microscopy of a mineral surface

    International Nuclear Information System (INIS)

    Scanning probe imaging in a shear force mode allows for the characterization of in-plane surface properties. In a standard AFM, shear force imaging can be realized by the torsional resonance mode. In order to investigate the imaging conditions on mineral surfaces, a torsional resonance mode atomic force microscope was operated in amplitude (AM) and frequency modulation (FM) feedback. Freshly cleaved chlorite was investigated, which showed brucite-like and talc-like surface areas. In constant amplitude FM mode, a slight variation in energy dissipation was observed between both surfaces. Amplitude and frequency vs. distance curves revealed that the tip was in repulsive contact with the specimen during imaging.

  8. Focusing through a turbid medium by amplitude modulation with genetic algorithm

    Science.gov (United States)

    Dai, Weijia; Peng, Ligen; Shao, Xiaopeng

    2014-05-01

    Multiple scattering of light in opaque materials such as white paint and human tissue forms a volume speckle field, will greatly reduce the imaging depth and degrade the imaging quality. A novel approach is proposed to focus light through a turbid medium using amplitude modulation with genetic algorithm (GA) from speckle patterns. Compared with phase modulation method, amplitude modulation approach, in which the each element of spatial light modulator (SLM) is either zero or one, is much easier to achieve. Theoretical and experimental results show that, the advantage of GA is more suitable for low the signal to noise ratio (SNR) environments in comparison to the existing amplitude control algorithms such as binary amplitude modulation. The circular Gaussian distribution model and Rayleigh Sommerfeld diffraction theory are employed in our simulations to describe the turbid medium and light propagation between optical devices, respectively. It is demonstrated that the GA technique can achieve a higher overall enhancement, and converge much faster than others, and outperform all algorithms at high noise. Focusing through a turbid medium has potential in the observation of cells and protein molecules in biological tissues and other structures in micro/nano scale.

  9. Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

    Directory of Open Access Journals (Sweden)

    Miriam Jaafar

    2012-04-01

    Full Text Available We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode.

  10. Amplitude modulation of quantum-ion-acoustic wavepackets in electron-positron-ion plasmas: Modulational instability, envelope modes, extreme wavesa)

    Science.gov (United States)

    Rahman, Ata-ur-; Kerr, Michael Mc; El-Taibany, Wael F.; Kourakis, Ioannis; Qamar, A.

    2015-02-01

    A semirelativistic fluid model is employed to describe the nonlinear amplitude modulation of low-frequency (ionic scale) electrostatic waves in an unmagnetized electron-positron-ion plasma. Electrons and positrons are assumed to be degenerated and inertialess, whereas ions are warm and classical. A multiscale perturbation method is used to derive a nonlinear Schrödinger equation for the envelope amplitude, based on which the occurrence of modulational instability is investigated in detail. Various types of localized ion acoustic excitations are shown to exist, in the form of either bright type envelope solitons (envelope pulses) or dark-type envelope solitons (voids, holes). The plasma configurational parameters (namely, the relativistic degeneracy parameter, the positron concentration, and the ionic temperature) are shown to affect the conditions for modulational instability significantly, in fact modifying the associated threshold as well as the instability growth rate. In particular, the relativistic degeneracy parameter leads to an enhancement of the modulational instability mechanism. Furthermore, the effect of different relevant plasma parameters on the characteristics (amplitude, width) of these envelope solitary structures is also presented in detail. Finally, the occurrence of extreme amplitude excitation (rogue waves) is also discussed briefly. Our results aim at elucidating the formation and dynamics of nonlinear electrostatic excitations in superdense astrophysical regimes.

  11. Sustained Selective Attention to Competing Amplitude-Modulations in Human Auditory Cortex

    OpenAIRE

    Riecke, Lars; Scharke, Wolfgang; Valente, Giancarlo; Gutschalk, Alexander

    2014-01-01

    Auditory selective attention plays an essential role for identifying sounds of interest in a scene, but the neural underpinnings are still incompletely understood. Recent findings demonstrate that neural activity that is time-locked to a particular amplitude-modulation (AM) is enhanced in the auditory cortex when the modulated stream of sounds is selectively attended to under sensory competition with other streams. However, the target sounds used in the previous studies differed not only in t...

  12. Rhythmic arm cycling differentially modulates stretch and H-reflex amplitudes in soleus muscle.

    Science.gov (United States)

    Palomino, Andres F; Hundza, Sandra R; Zehr, E Paul

    2011-10-01

    During rhythmic arm cycling, soleus H-reflex amplitudes are reduced by modulation of group Ia presynaptic inhibition. This suppression of reflex amplitude is graded to the frequency of arm cycling with a threshold of 0.8 Hz. Despite the data on modulation of the soleus H-reflex amplitude induced by rhythmic arm cycling, comparatively little is known about the modulation of stretch reflexes due to remote limb movement. Therefore, the present study was intended to explore the effect of arm cycling on stretch and H-reflex amplitudes in the soleus muscle. In so doing, additional information on the mechanism of action during rhythmic arm cycling would be revealed. Although both reflexes share the same afferent pathway, we hypothesized that stretch reflex amplitudes would be less suppressed by arm cycling because they are less inhibited by presynaptic inhibition. Failure to reject this hypothesis would add additional strength to the argument that Ia presynaptic inhibition is the mechanism modulating soleus H-reflex amplitude during rhythmic arm cycling. Participants were seated in a customized chair with feet strapped to footplates. Three motor tasks were performed: static control trials and arm cycling at 1 and 2 Hz. Soleus H-reflexes were evoked using single 1 ms pulses of electrical stimulation delivered to the tibial nerve at the popliteal fossa. A constant M-wave and ~6% MVC activation of soleus were maintained across conditions. Stretch reflexes were evoked using a single sinusoidal pulse at 100 Hz given by a vibratory shaker placed over the triceps surae tendon and controlled by a custom-written LabView program. Results demonstrated that rhythmic arm cycling that was effective for conditioning soleus H-reflexes did not show a suppressive effect on the amplitude of the soleus stretch reflex. We suggest this indicates that stretch reflexes are less sensitive to conditioning by rhythmic arm movement, as compared to H-reflexes, due to the relative insensitivity to Ia presynaptic inhibition. PMID:21901451

  13. Super-oscillation focusing lens based on continuous amplitude and binary phase modulation.

    Science.gov (United States)

    Wen, Zhongquan; He, Yinghu; Li, Yuyan; Chen, Li; Chen, Gang

    2014-09-01

    In this paper, we numerically demonstrate the advantage of utilizing continuous amplitude and phase modulation in super-oscillation focusing lens design. Numerical results show that compared with simple binary amplitude modulation, continuous amplitude and phase modulation can greatly improve the super-oscillation focusing performance by increasing the central lobe intensity and the ratio of its energy to the total energy, reducing the sidelobe intensity, and substantially extending the field of view. Our study also reveals the role of phase distribution in reducing the spatial frequency bandwidth of the super-oscillation optical field on the focal plane. Based on continuous amplitude and binary phase modulation, a lens was designed with double layer metal slit array for wavelength of 4.6 µm. COMSOL is used to carry out the 2D simulation. The lens focal length is 40.18? and the focal spot FWHM is 0.308?. Two largest sidelobes are located right next to the central lobe with intensity about 40% of the central lobe intensity. Except for the two sidelobes, other sidelobes have intensity less than 25% of the central lobe intensity, which leads to a clear field of view on the whole focal plane. PMID:25321591

  14. Radar transponder operation with compensation for distortion due to amplitude modulation

    Science.gov (United States)

    Ormesher, Richard C. (Albuquerque, NM); Tise, Bertice L. (Albuquerque, NM); Axline, Jr., Robert M. (Albuquerque, NM)

    2011-01-04

    In radar transponder operation, a variably delayed gating signal is used to gate a received radar pulse and thereby produce a corresponding gated radar pulse for transmission back to the source of the received radar pulse. This compensates for signal distortion due to amplitude modulation on the retransmitted pulse.

  15. Pulsational frequency and amplitude modulation in the ? Sct star KIC 7106205

    Science.gov (United States)

    Bowman, Dominic M.; Kurtz, Donald W.

    2014-10-01

    Analysis of the Kepler ? Sct star KIC 7106205 showed amplitude modulation in a single pressure mode, whilst all other pressure and gravity modes remained stable in amplitude and phase over the 1470 d length of the data set. The Kepler data set was divided into a series with time bins of equal length for which consecutive Fourier transforms were calculated. An optimum fixed frequency, calculated from a least-squares fit of all data, allowed amplitude and phase of each pulsation mode for each time bin to be tracked. The single pressure mode at ? = 13.3942 d-1 changed significantly in amplitude, from 5.16 ± 0.03 to 0.53 ± 0.06 mmag, but also varied quasi-sinusoidally in phase, with a characteristic period similar to the length of the data set. All other p and g modes were stable in both amplitude and phase, which is clear evidence that the visible pulsation mode energy is not conserved within this star. Possible causes of the observed amplitude and phase modulation and the missing mode energy are discussed.

  16. Amplitude and phase modulation of time-energy entangled two-photon states

    CERN Document Server

    Zäh, F; Feurer, T; 10.1364/OE.16.016452

    2009-01-01

    We experimentally demonstrate amplitude and phase modulation of a time-energy entangled two-photon wave function. The entangled photons are produced by spontaneous parametric down-conversion, spectrally dispersed in an prism compressor, modulated in amplitude and/or phase, and detected in coincidence by sum-frequency generation. First, we present a Fourier optical analysis of the optical setup yielding an analytic expression for the resulting field distribution at the exit plane of the shaping apparatus. We then introduce amplitude and/or phase shaping and present results which can only be obtained through a combination of the two. Specifically, we use a shaper-based interferometer to measure the two-photon interference of an almost bandwidth-limited two-photon wave function.

  17. Optical amplitude modulation extinction by a deep saturated ultra-long semiconductor optical amplifier.

    Science.gov (United States)

    Ribeiro, Napoleão S; Cavacalcante, André L R; Gallep, Cristiano M; Conforti, Evandro

    2010-12-20

    The recovery of an optical carrier with the deletion of its amplitude modulation is introduced using a deeply saturated ultra-long semiconductor optical amplifier (UL-SOA). The experimental results were achieved for input signal bit rates up to 12.5 Gbps with high extinction ratio (up to 13.9 dB). The influence of parameters such as UL-SOA bias current, optical bandwidth, signal input power, modulation depth and bit rate are analyzed including the carrier spectral broadening effects due to the self-phase modulation effect. PMID:21197008

  18. Tunable Pulse Amplitude and Position Modulation Technique for Reliable Optical Wireless Communication Channels

    Directory of Open Access Journals (Sweden)

    Mark S. Leeson

    2007-03-01

    Full Text Available

    Modulation techniques have attracted increasing attention in optical wireless communications. Basic schemes such as on off keying (OOK, pulse amplitude modulation (PAM and pulse position modulation (PPM have been validated as suitable for the optical wireless channel. This paper starts from the analysis of these three modulation schemes in terms of their power and bandwidth requirements. As a result, a new tunable hybrid modulation technique is proposed. The proposed modulation scheme takes the real time channel conditions into account, which is different from other schemes. By employing amplitude and position modulation selectively, a guaranteed system performance can be secured, without compromising power and bandwidth efficiency. This is also a new approach to realize reliable optical wireless links.

  19. A Compact QPSK Modulator with Low Amplitude and Phase Imbalance for Remote Sensing Applications

    KAUST Repository

    Ghaffar, Farhan Abdul

    2012-09-30

    A new, compact and wide-band Quadrature Phase Shift Keying (QPSK) modulator is presented for remote sensing applications. The microstrip-based modulator employs quadrature hybrid coupler, Wilkinson divider, rat race coupler and GaAs MESFET switches. It is designed to be part of an X band remote sensing transmitter with a center frequency of 8.25GHz. The fabricated module demonstrates the lowest reported amplitude and phase imbalances (0.1dB and 0.4° respectively) around its center frequency. The modulation, tested up to 160 Mbps data rate, displays carrier suppression greater than 30 dB. With negligible DC power consumption and low insertion loss, it operates for a wide bandwidth of 3 GHz (7-10 GHz). The effect of amplitude and phase imbalance is investigated on the performance of the modulator. Finally, a transmitter employing this modulator exhibits an excellent overall Error Vector Magnitude (EVM) of around 8 % that is considerably low as compared to the typically obtained values for such transmitters.

  20. Amplitude Apodizers Encoded onto Fresnel Lenses Implemented on a Phase-Only Spatial Light Modulator.

    Science.gov (United States)

    Márquez, A; Iemmi, C; Escalera, J C; Campos, J; Ledesma, S; Davis, J A; Yzuel, M J

    2001-05-10

    We show that both a lens and a nonuniform amplitude transmission filter can be encoded simultaneously onto a twisted nematic liquid-crystal spatial light modulator (SLM) working in the phase-only mode. The inherent equivalent apodization that is due to the pixelated structure of the SLM is compensated for. In addition, different types of nonuniform transmission pupil such as transverse apodizing, transverse hyperresolving, and axial hyperresolving (multifocusing) filters are implemented. The excellent agreement between numerical and experimental results shows the capability of this method to encode amplitude apodizers on a phase-only SLM. PMID:18357241

  1. Anamorphic optical transformation of an amplitude spatial light modulator to a complex spatial light modulator with square pixels [invited].

    Science.gov (United States)

    Kim, Hwi; Hwang, Chi-Young; Kim, Kwang-Soo; Roh, Jinyoung; Moon, Woonchan; Kim, Sungmin; Lee, Beom-Ryoel; Oh, Seungtaik; Hahn, Joonku

    2014-09-20

    A method is proposed for the construction of a square pixel complex spatial light modulator (SLM) from a commercial oblong full-high-definition (full-HD) amplitude SLM using an anamorphic optical filter. In the proposed scheme, one half-band of the optical Fourier transform of the amplitude-only spatial light field is rejected in the optical Fourier plane and the other half-band is reformatted to be an effective complex SLM with square pixels. This has an advantage in the viewing window plane since the shape of the viewing window becomes square and more ideal for observers who watch the hologram contents through it. For optimal transformation, the amplitude computer generated hologram encoding scheme was developed. Mathematical modeling of the proposed system is described herein, and it was experimentally demonstrated that the effective complex SLM displays complex holographic three-dimensional images with a clear depth discrimination effect. PMID:25322122

  2. Conceptual design of a dispersion interferometer using a ratio of modulation amplitudes

    International Nuclear Information System (INIS)

    Since a dispersion interferometer is free mechanical vibrations, it does not need a vibration compensation system even for a probe beam with a short wavelength. This paper describes a new signal processing of the dispersion interferometer using a ratio of modulation amplitudes with a photoelastic modulator. The proposed method is immune to changes in detected signal intensities, thus making the signal processing system simple. Designs of the optical system of the dispersion interferometer for proof of principle, especially specification of a nonlinear optical crystal, are also shown. (author)

  3. Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

    Science.gov (United States)

    Trosin, Barry James

    2007-01-01

    Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

  4. Superpixel-based spatial amplitude and phase modulation using a digital micromirror device

    CERN Document Server

    Goorden, Sebastianus A; Mosk, Allard P

    2014-01-01

    We present a superpixel method for full spatial phase and amplitude control of a light beam using a digital micromirror device (DMD) combined with a spatial filter. By spatial filtering we combine square regions of nearby micromirrors into superpixels. At each superpixel we are able to independently modulate the phase and the amplitude of light, while retaining a high resolution and all advantages of a DMD such as its very high speed. The method achieves a measured fidelity $F=0.98$ for a high resolution target field with fully independent phase and amplitude and a calculated fidelity $F=0.99993$ for the LG$_{10}$ orbital angular momentum mode, offering one to three orders of magnitude reduction of error with respect to the state of the art Lee holography method.

  5. On the modulational instability of large amplitude waves in supersonic boundary layers

    Science.gov (United States)

    Hall, Philip; Papageorgiou, Demetrios T.

    1995-01-01

    The evolution of large amplitude Tollmien-Schlichting waves in a supersonic boundary layer is investigated. Disturbances which have their wavenumber and frequency slowly varying in time and space are described using a phase equation type of approach. Unlike the incompressible case we find that the initial bifurcation to a finite amplitude Tollmien-Schlichting wave is subcritical for most Mach numbers. In fact the bifurcation is only supercritical for a small range of Mach numbers and even then for only a finite range of wave propagation angles. The modulational instability of large amplitude wavetrains is considered and is shown to be governed by an equation similar to Burgers equation but with the viscous term replaced by a fractional derivative. A numerical investigation of the solution of this equation is described. It is shown that uniform wavetrains are unstable.

  6. Terminal residue hydrophobicity modulates transmembrane helix-helix interactions.

    Science.gov (United States)

    Ng, Derek P; Deber, Charles M

    2014-06-17

    Central to the formation of tertiary structure in membrane protein folding is the presence of amino acid sequence motifs (such as "small-XXX-small" segments) in the TM segments that promote interaction-compatible surfaces through which the TM ?-helices interact. Here, we sought to elucidate additional factors that may work in tandem to dictate the ultimate interaction fate of TM-embedded segments. In this context, we used proteolipid protein (PLP), the major protein from central nervous system myelin for which mutant-dependent non-native oligomerization has been implicated in neurological disorders, to explore the specific effects of TM boundary residues (the membrane entry and exit points), keying on the secondary structure and self-association of peptides corresponding to the PLP TM2 ?-helix (wild-type sequence ??AFQYVIYGTASFFFLYGALLLAEGF??). Using gel electrophoresis, circular dichroism, and Förster resonance energy transfer in the membrane-mimetic detergent sodium dodecyl sulfate (SDS), we found that mutation of F90 to residues such as A, I, L, or V maintains the onset of TM2-TM2 dimerization, whereas mutation to E, G, Q, N, S, or T abrogates dimer formation. We attribute this sensitivity to changes in local hydrophobicity, viz., a decrease in hydrophobicity reduces local lipid-peptide interactions, which in turn disrupts peptide ?-helicity and hence the effectiveness of an incipient interaction-compatible surface. Our results show that the secondary structure and oligomeric state of PLP TM2 Lys-tagged peptides are significantly modulated by the specific nature of their C-terminal boundary residue, thus providing insight as to how point mutations, particularly where they produce disease states, can compromise the folding process. PMID:24857611

  7. State-dependent representation of amplitude-modulated noise stimuli in rat auditory cortex.

    OpenAIRE

    Marguet, S. L.; Harris, K. D.

    2011-01-01

    Cortical responses can vary greatly between repeated presentations of an identical stimulus. Here we report that both trial-to-trial variability and faithfulness of auditory cortical stimulus representations depend critically on brain state. A frozen amplitude-modulated white noise stimulus was repeatedly presented while recording neuronal populations and local field potentials (LFPs) in auditory cortex of urethane-anesthetized rats. An information-theoretic measure was used to predict neuron...

  8. Effect of amplitude modulation of gravitational vibration on convective instability of reaction fronts in porous media

    OpenAIRE

    Allali, K.; Belhaq, M.

    2013-01-01

    This paper studies the influence of periodic and quasi-periodic amplitudemodulations of gravitational vibration on the convective instabilityof reaction fronts in porous media. Specifically, two cases of amplitudemodulation are investigated. In the first case, we consider that thefrequency ?2 of the amplitude modulation is either double or half thefrequency of the basic gravitational vibration ?1. In this case the modulatedgravitational vibration remains periodic. In the second case, weassu...

  9. Broadband homonuclear TOCSY with amplitude and phase-modulated RF mixing schemes.

    Science.gov (United States)

    Kirschstein, Anika; Herbst, Christian; Riedel, Kerstin; Carella, Michela; Leppert, Jörg; Ohlenschläger, Oliver; Görlach, Matthias; Ramachandran, Ramadurai

    2008-04-01

    We have explored the design of broadband scalar coupling mediated (13)C-(13)C and cross-relaxation suppressed (1)H-(1)H TOCSY sequences employing phase/amplitude modulated inversion pulses. Considering a variety of supercycles, pulsewidths and a RF field strength of 10 kHz, the Fourier coefficients defining the amplitude and phase modulation profiles of the 180 degrees pulses were optimised numerically so as to obtain efficient magnetisation transfer within the desired range of resonance offsets. The coherence transfer characteristics of the mixing schemes were assessed via numerical simulations and experimental measurements and were compared with commonly used sequences based on rectangular RF pulses. The efficacies of the clean (1)H-(1)H TOCSY sequences were also examined via numerical simulations for application to weakly oriented systems and sequences with efficient, broadband and clean dipolar transfer characteristics were identified. In general, the amplitude and phase modulated TOCSY sequences presented here have moderately better performance characteristics than the sequences currently employed in biomolecular NMR spectroscopy. PMID:18317934

  10. Cyclic pitch for the control of wind turbine noise amplitude modulation

    DEFF Research Database (Denmark)

    Bertagnolio, Franck; Aagaard Madsen, Helge

    2014-01-01

    Using experimental data acquired during a wind turbine measurement campaign, it is shown that amplitude modulation of aerodynamic noise can be generated by the rotating blades in conjunction with the atmospheric wind shear. As an attempt to alleviate this phenomenon, a control strategy is designed in form of a cyclic pitch of the blades. As a side effect, it is shown that it is also possible to reduce fatigue load on the blade using this cyclic pitch. The main goal is to reduce both amplitude modulation and fatigue load without compromising the energy harvested from the wind. A simulation tool that can model the different aerodynamic and aeroacoustic aspects of the study is presented. Parameters controlling the cyclic pitch are optimized in order to reduce amplitude modulation and/or fatigue load to a minimum. It is shown that such a minimum can be found and that benefit may be achieved if such a strategy is to be implemented on an actual wind turbine, though at the expense of an increased wear and tear of the pitch control system.

  11. Detection of sinusoidal amplitude modulation in logarithmic frequency sweeps across wide regions of the spectrum.

    Science.gov (United States)

    Hsieh, I-Hui; Saberi, Kourosh

    2010-04-01

    Many natural sounds such as speech contain concurrent amplitude and frequency modulation (AM and FM), with the FM components often in the form of directional frequency sweeps or glides. Most studies of modulation coding, however, have employed one modulation type in stationary carriers, and in cases where mixed-modulation sounds have been used, the FM component has typically been confined to an extremely narrow range within a critical band. The current study examined the ability to detect AM signals carried by broad logarithmic frequency sweeps using a 2-alternative forced-choice adaptive psychophysical design. AM-detection thresholds were measured as a function of signal modulation rate and carrier sweep frequency region. Thresholds for detection of AM in a sweep carrier ranged from -8 dB for an AM rate of 8 Hz to -30 dB at 128 Hz. Compared to thresholds obtained for stationary carriers (pure tones and filtered Gaussian noise), detection of AM carried by frequency sweeps substantially declined at low (12 dB at 8 Hz) but not high modulation rates. Several trends in the data, including sweep- versus stationary-carrier threshold patterns and effects of frequency region were predicted from a modulation filterbank model with an envelope-correlation decision statistic. PMID:20144700

  12. Differential pulse amplitude modulation for multiple-input single-output OWVLC

    Science.gov (United States)

    Yang, S. H.; Kwon, D. H.; Kim, S. J.; Son, Y. H.; Han, S. K.

    2015-01-01

    White light-emitting diodes (LEDs) are widely used for lighting due to their energy efficiency, eco-friendly, and small size than previously light sources such as incandescent, fluorescent bulbs and so on. Optical wireless visible light communication (OWVLC) based on LED merges lighting and communications in applications such as indoor lighting, traffic signals, vehicles, and underwater communications because LED can be easily modulated. However, physical bandwidth of LED is limited about several MHz by slow time constant of the phosphor and characteristics of device. Therefore, using the simplest modulation format which is non-return-zero on-off-keying (NRZ-OOK), the data rate reaches only to dozens Mbit/s. Thus, to improve the transmission capacity, optical filtering and pre-, post-equalizer are adapted. Also, high-speed wireless connectivity is implemented using spectrally efficient modulation methods: orthogonal frequency division multiplexing (OFDM) or discrete multi-tone (DMT). However, these modulation methods need additional digital signal processing such as FFT and IFFT, thus complexity of transmitter and receiver is increasing. To reduce the complexity of transmitter and receiver, we proposed a novel modulation scheme which is named differential pulse amplitude modulation. The proposed modulation scheme transmits different NRZ-OOK signals with same amplitude and unit time delay using each LED chip, respectively. The `N' parallel signals from LEDs are overlapped and directly detected at optical receiver. Received signal is demodulated by power difference between unit time slots. The proposed scheme can overcome the bandwidth limitation of LEDs and data rate can be improved according to number of LEDs without complex digital signal processing.

  13. Inner/outer layer interactions in turbulent boundary layers: A refined measure for the large-scale amplitude modulation mechanism

    Science.gov (United States)

    Bernardini, Matteo; Pirozzoli, Sergio

    2011-06-01

    The amplitude modulation (AM) imparted by the outer layer large-scale motions on the near-wall turbulence is studied through direct numerical simulation of compressible boundary layer flow at moderate Reynolds number. Mathis et al. [J. Fluid Mech. 628, 311 (2009)] introduced an amplitude modulation coefficient to quantify this effect, whereby carrier and modulated signals are decoupled through a procedure based on the Hilbert transform of the streamwise velocity signals. However, Schlatter and Örlü [Phys. Fluids 22, 051704 (2010)] have recently shown that a non-zero amplitude modulation coefficient is closely associated to a non-zero value of the velocity skewness, and therefore, it does not necessarily reflect genuine physics. In this paper, the analysis is extended through systematic use of the two-point amplitude modulation correlation, which is shown to be a refined measure of the top-down influence of large-scale outer events on the inner part of the boundary layer.

  14. A novel amplitude modulated triangular carrier gain linearization technique for SPWM inverter

    Directory of Open Access Journals (Sweden)

    Ramkumar Subburam

    2009-01-01

    Full Text Available This paper presents a new method to extend the linearity of the sinusoidal pulse width modulation (SPWM to full range of the pulse dropping region. The proposed amplitude modulated triangular carrier PWM method (AMTCPWM increases the dynamic range of the SPWM control and eliminates the need of nonlinear modulation in the pulse dropping region to reach the square wave boundary. The novel method combines the spectral quality of SPWM with the efficient single-mode linear control. A simple analytical characterization of the exact method is presented and its effectiveness is demonstrated using simulation for the basic single-phase H-bridge inverter circuit. The hardware results of the designed prototype inverter are presented to validate the betterment of the novel scheme. .

  15. Limitations on accurate shape determination using amplitude modulation atomic force microscopy

    International Nuclear Information System (INIS)

    The limitations of amplitude modulation atomic force microscopy to accurately measure the shape or form of features are investigated. The control feedback loop and the dynamics of the cantilever limit the response time of the atomic force microscope. Simply subtracting appropriately scaled amplitude (error) signal from the topography data significantly improves the accuracy of the data and can correct for the slow response time of the feedback loop. Two mechanisms were found to induce topographic errors independent of scan speed. The first is the change in tip/surface interaction at a step edge observed by comparison with results from a ‘virtual’ sample. The second is due to friction between the probe and sample but only for a specifically oriented step edge determined by the direction of oscillation of the cantilever. -- Highlights: ? Three sources of error that effect shape measurements using an AFM are discussed. ? Focus is solely on amplitude modulation AFM. ? A simple scheme corrects for errors due to limitations in the feedback loop. ? Effect of changing tip-surface interaction at step edge to shape is quantified. ? Friction between tip and sample distorts measured shape.

  16. Probe-surface interaction mapping in amplitude modulation atomic force microscopy by integrating amplitude-distance and amplitude-frequency curves

    International Nuclear Information System (INIS)

    The procedure integrating independent amplitude-distance and amplitude-frequency measurements into a single routine with two variables (frequency and distance) has been developed. The domains of attraction and repulsion regimes of probe-surface interactions are clearly identified on two-dimensional patterns in frequency-distance space due to the stepwise change in a slope of constant amplitude lines and their shear on boundaries. Pattern evolution with the driving amplitude variation was studied, and three characteristic pattern types were selected. The topology of patterns obtained at intermediate drivings indicates that the probe-surface interaction is attractive at large and low cantilever-surface separations being repulsive at intermediate separations

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-28

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Ramos, Jorge R.

    2014-07-01

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

  20. Counterpropagation and amplitude modulation of rolls in a broken-symmetry electroconvection experiment

    Science.gov (United States)

    Spiegel, Dan

    2005-11-01

    We report a liquid-crystal electroconvection pattern-formation experiment along a narrow strip in which the translational symmetry is broken with a laser-induced thermal gradient. In contrast with other broken-symmetry patterns that display a uniform drift, we observe rolls that counterpropagate into a sink point and a strong temporally periodic amplitude modulation near this point. The time dependence of the amplitude at a fixed position is periodic but not sinusoidal. On the basis of experimental spacetime contours and wavenumber profiles, along with a measurement of the change in the roll-drift frequency with applied voltage at a fixed control parameter, we propose a simple qualitative model based on (1) the enhancement of thermal transport due to advection, and (2) a hyperbolic-tangent solution to the Ginzburg-Landau equation that is relevant near the Eckhaus boundary.

  1. Encoding of amplitude modulations by auditory neurons of the locust: influence of modulation frequency, rise time, and modulation depth

    OpenAIRE

    Wohlgemuth, Sandra; Vogel, Astrid; Ronacher, Bernhard

    2010-01-01

    Using modulation transfer functions (MTF), we investigated how sound patterns are processed within the auditory pathway of grasshoppers. Spike rates of auditory receptors and primary-like local neurons did not depend on modulation frequencies while other local and ascending neurons had lowpass, bandpass or bandstop properties. Local neurons exhibited broader dynamic ranges of their rate MTF that extended to higher modulation frequencies than those of most ascending neurons. We found no indica...

  2. Encoding of amplitude modulations by auditory neurons of the locust: influence of modulation frequency, rise time, and modulation depth.

    Science.gov (United States)

    Wohlgemuth, Sandra; Vogel, Astrid; Ronacher, Bernhard

    2011-01-01

    Using modulation transfer functions (MTF), we investigated how sound patterns are processed within the auditory pathway of grasshoppers. Spike rates of auditory receptors and primary-like local neurons did not depend on modulation frequencies while other local and ascending neurons had lowpass, bandpass or bandstop properties. Local neurons exhibited broader dynamic ranges of their rate MTF that extended to higher modulation frequencies than those of most ascending neurons. We found no indication that a filter bank for modulation frequencies may exist in grasshoppers as has been proposed for the auditory system of mammals. The filter properties of half of the neurons changed to an allpass type with a 50% reduction of modulation depths. Contrasting to reports for mammals, the sensitivity to small modulation depths was not enhanced at higher processing stages. In ascending neurons, a focus on the range of low modulation frequencies was visible in the temporal MTFs, which describe the temporal locking of spikes to the signal envelope. To investigate the influence of stimulus rise time, we used rectangularly modulated stimuli instead of sinusoidally modulated ones. Unexpectedly, steep stimulus onsets had only small influence on the shape of MTF curves of 70% of neurons in our sample. PMID:20865417

  3. Theoretical analysis and computer simulation of the amplitude of electrostatic plasma waves excited by a power-modulated laser beam

    International Nuclear Information System (INIS)

    The amplitude of electrostatic ion cyclotron waves excited by a power-modulated laser beam is compared with those predicted by theoretical analysis and computer simulation. It is shown that the wave amplitude obtained experimentally roughly agrees with the theoretical value within an order of magnitude, while the amplitude in the computer simulation is consistent with the theoretical values within a factor of 1.5. (author)

  4. Theory of amplitude modulated electrostatic force microscopy for dielectric measurements in liquids at MHz frequencies

    International Nuclear Information System (INIS)

    A theoretical analysis of amplitude modulated electrostatic force microscopy (AM-EFM) in liquid media at MHz frequencies, based on a simple tip–sample parallel plate model, is presented. The model qualitatively explains the main features of AM-EFM in liquid media and provides a simple explanation of how the measured electric forces are affected by: the frequency of the applied voltage, the tip–sample distance, the ionic concentration, the relative dielectric constant of the solution, and the relative dielectric constant and thickness of the sample. These results provide a simple framework for the design of AM-EFM measurements for localized dielectric characterization in liquid media. (paper)

  5. Slow light of an amplitude modulated Gaussian pulse in electromagnetically induced transparency medium

    CERN Document Server

    Tang, Wenzhuo; Liu, Yu; Guo, Hong

    2009-01-01

    The slow light effects of an amplitude modulated Gaussian (AMG) pulse in a cesium atomic vapor are presented. In a single-$\\Lambda$ type electromagnetically induced transparency (EIT) medium, more severe distortion is observed for an AMG pulse than a Gaussian one. Using Fourier spectrum analysis, we find that the distortion, as well as the loss, is dominantly caused by linear absorption than dispersion. Accordingly, a compensation method is proposed to reshape the slow light pulse based on the transmission spectrum. In addition, we find a novel way to obtain simultaneous slow and fast light.

  6. Lisa amplitude modulation: A study of the angular resolution of LISA for monochromatic gravitational waves

    International Nuclear Information System (INIS)

    We present formulae for the amplitude modulation of the X,Y and Z TDI combinations for monochromatic gravitational waves and use these to study the LISA angular resolution in the case of large SNR. The angular resolution, ??/(0.1 * SNR), is found to lie between 2 deg. and 5 deg. and is somewhat dependent on the ecliptic colatitude angle (?), on the polarisation (h+,hx) and much less on the ecliptic longitude angle (?). Comparisons with other studies are presented. Future studies will treat the case of small SNR.

  7. A New Selective Harmonic Elimination Pulse- Width and Amplitude Modulation (SHEPWAM) for Drive Applications

    DEFF Research Database (Denmark)

    Ghoreishy, Hoda; Varjani, Ali Yazdian

    2013-01-01

    Compared to the conventional selective harmonic elimination-pulse width modulation (SHE-PWM), the selective harmonic elimination-pulse width and amplitude modulation (SHE-PWAM) control strategy results in significant improvements in the performance of CHB inverters. This fact is due to considering the optimization of the CHB dc sources’ values along with the optimized switching angles. This paper proposes a new SHE-PWAM control strategy and its realization in a drive application. Analysis and simulations are carried out on a fivelevel CHB inverter. Experimental verifications also validate the simulation results. The results demonstrate that the new SHEPWAM technique improves the performance of the drive compared to the conventional SHE-PWM.

  8. Density profile measurements by amplitude modulation reflectometry on the TJ-1 tokamak

    International Nuclear Information System (INIS)

    Amplitude Modulation (AM) reflectometry has been proposed as an alternative method to the more traditional swept frequency reflectometry systems which can be strongly affected by the presence of plasma density fluctuations. Compared to the time domain systems, the time measurements are replaced in AM reflectometry by much simpler phase delay measurements. In AM reflectometry, the time delay of the microwave beam propagating to the reflecting layer and back is directly obtained through the phase delay of the modulating envelope, which is directly measured in a linear (0-2?) phase meter. This method avoids operation with multifringe counters and is a very attractive alternative for real time determination of the plasma position and density profile. In order to achieve real time density profile monitoring, fast analysis methods are necessary, first results of Neural Networks application to the problem of fast inversion of the density profile are shown. (author) 3 refs., 5 figs

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

    DEFF Research Database (Denmark)

    Iglesias Olmedo, Miguel; Zuo, Tianjian

    2014-01-01

    Short range optical data links are experiencing bandwidth limitations making it very challenging to cope with the growing data transmission capacity demands. Parallel optics appears as a valid short-term solution. It is, however, not a viable solution in the long-term because of its complex optical packaging. Therefore, increasing effort is now put into the possibility of exploiting higher order modulation formats with increased spectral efficiency and reduced optical transceiver complexity. As these type of links are based on intensity modulation and direct detection, modulation formats relying on optical coherent detection can not be straight forwardly employed. As an alternative and more viable solution, this paper proposes the use of carrierless amplitude phase (CAP) in a novel multiband approach (MultiCAP) that achieves record spectral efficiency, increases tolerance towards dispersion and bandwidth limitations and reduces the complexity of the transceiver. We report on numerical simulations and experimental demonstrations with capacity beyond 100 Gb/s transmission using a single externally modulated laser (EML). In addition, an extensive comparison with conventional CAP is also provided. The reported experiment uses MultiCAP to achieve 102.4 Gb/s transmission, corresponding to a data payload of 95.2 Gb/s error free transmission by using a 7% forward error correction (FEC) code. The signal is successfully recovered after 15 km of standard single mode fiber (SSMF) in a system limited by a 3 dB bandwidth of 14 GHz.

  10. Amplitude modulation depth discrimination in hearing-impaired and normal-hearing listeners

    DEFF Research Database (Denmark)

    Ewert, Stephan D.; Volmer, Jutta

    2008-01-01

    The processing of amplitude modulations (AM) of sounds is assumed to be crucial for decoding and understanding of speech in humans. Since hearing-impaired (HI) listeners often suffer from severely hampered speech intelligibility, particularly in reverberant or noisy environments, they might also show degraded performance in AM processing tasks. However, several studies indicated a similar or even better performance in AM detection tasks for sensorineural HI listeners than for normal hearing (NH) listeners when reduced audibility was compensated. In addition to AM detection, this study investigates the differential processing of amplitude modulation depth in HI and NH listeners. AM-depth discrimination of a 4-, 8-, and 30-Hz sinusoidal AM, imposed on a 1- or 4-kHz pure-tone carrier, was measured. The AM of the standard ranged from being well detectable to near threshold. AM-depth discrimination thresholds strongly varied among HI listeners and were elevated in comparison to NH for high standard depths. A model of AM processing is suggested incorporating an individually adjusted simulation of the auditory periphery. To account for the data of HI listeners, however, the key element appeared to be an increased internal noise in the AM-depth domain. Consequences for speech perception are discussed.

  11. Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies

    Directory of Open Access Journals (Sweden)

    Frederico P. Costa

    2013-11-01

    Full Text Available In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF electromagnetic fields (EMF, which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer.

  12. Perceptual interaction between carrier periodicity and amplitude modulation in broadband stimuli: A comparison of the autocorrelation and modulation-filterbank model

    DEFF Research Database (Denmark)

    Stein, A.; Ewert, Stephan

    2005-01-01

    Recent temporal models of pitch and amplitude modulation perception converge on a relatively realistic implementation of cochlear processing followed by a temporal analysis of periodicity. However, for modulation perception, a modulation filterbank is applied whereas for pitch perception, autocorrelation is applied. Considering the large overlap in pitch and modulation perception, this is not parsimonious. Two experiments are presented to investigate the interaction between carrier periodicity, which produces strong pitch sensations, and envelope periodicity using broadband stimuli. Results show that in the presence of carrier periodicity, detection of amplitude modulation is impaired throughout the tested range (8-1000 Hz). On the contrary, detection of carrier periodicity in the presence of an additional amplitude modulation is impaired only for very low frequencies below the pitch range (<33 Hz). Predictions of a generic implementation of a modulation-filterbank model and an autocorrelation model are compared to the data. Both models were too insensitive to high-frequency envelope or carrier periodicity and to infra-pitch carrier periodicity. Additionally, both models simulated modulation detection quite well but underestimated the detrimental effect of carrier periodicity on modulation detection. It is suggested that a hybrid model consisting of bandpass envelope filters with a ripple in their passband may provide a functionally successful and physiologically plausible basis for a unified model of auditory periodicity extraction.

  13. Probing the adsorption of weak acids on graphite using amplitude modulation-frequency modulation atomic force microscopy.

    Science.gov (United States)

    Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; Gamal El-Din, Mohamed

    2015-03-17

    Recent thermodynamics calculations and adsorption isotherms showed that the adsorption of a self-assembled layer (SAL) of ionized weak acids to carbon was attributed to the negatively charged hydrogen bonding (-CAHB), yet the direct visualization and characterization of this adsorption behavior have not been reported. Here, an amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM) technique was applied to discriminate the adsorption of decanoic acids (DA) on highly ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed that the adsorption of SAL was driven by the formation of -CAHB with negatively charged functional groups of HOPG. Multilayer adsorption could occur over the adsorbed ionized SAL, leading to the development of aggregates. AM-FM AFM imaging showed that the adsorption of the DA molecules forming aggregates occurred only for the HOPG-functionalized steps, while DA molecules were found to adsorb over the entire functionalized HOPG surface after water-plasma treatment, as evident from the frequency shifts identified in AFM images. PMID:25710305

  14. A computational model of inferior colliculus responses to amplitude modulated sounds in young and aged rats

    Directory of Open Access Journals (Sweden)

    AravindakshanParthasarathy

    2012-11-01

    Full Text Available The inferior colliculus (IC receives ascending excitatory and inhibitory inputs from multiple sources, but how these auditory inputs converge to generate IC spike patterns is poorly understood. Simulating patterns of in vivo spike train data from cellular and synaptic models creates a powerful framework to identify factors that contribute to changes in IC responses, such as those resulting in age-related loss of temporal processing. A conductance-based single neuron IC model was constructed, and its responses were compared to those observed during in vivo IC recordings in rats. IC spike patterns were evoked using amplitude-modulated (AM tone or noise carriers at 20-40 dB above threshold and were classified as low-pass, band-pass, band-reject, all-pass, or complex based on their rate modulation transfer function (rMTF tuning shape. Their temporal modulation transfer functions (tMTFs were also measured. These spike patterns provided experimental measures of rate, vector strength and firing pattern for comparison with model outputs. Patterns of excitatory and inhibitory synaptic convergence to IC neurons were based on anatomical studies and generalized input tuning for modulation frequency. Responses of modeled ascending inputs were derived from experimental data from previous studies. Adapting and sustained IC intrinsic models were created, with adaptation created via calcium-activated potassium currents. Short-term synaptic plasticity was incorporated into the model in the form of synaptic depression, which was shown to have a substantial effect on the magnitude and time course of the IC response. The most commonly observed IC response subtypes were recreated and enabled dissociation of inherited response properties from those that were generated in IC. Furthermore, the model was used to make predictions about the consequences of reduction in inhibition for age-related loss of temporal processing due to a reduction in GABA seen anatomically with age.

  15. Amplitude modulated Bloch oscillations of photon probability distribution in a cavity–atom system

    Science.gov (United States)

    Zhang, G.; Hu, WH; Song, Z.

    2015-04-01

    We study the dynamics of the Rabi Hamiltonian in the medium coupling regime with ?ft| g/? \\right|? 0.07, where g is the atom-field coupling constant and ? is the field frequency, for the quantum state with average photon number \\bar{n}? {{10}4}. We map the original Hamiltonian to an effective one, which describes a tight-binding chain subjected to a staggered linear potential. It is shown that the photon probability distribution of a Gaussian-type state exhibits amplitude-modulated Bloch oscillations (BOs), which are a superposition of two conventional BOs with a half-BO-period delay between them and are essentially another type of Bloch–Zener oscillation. The probability transition between the two BOs can be controlled and suppressed by the ratio g\\sqrt{{\\bar{n}}}/? , as well as the in-phase resonant oscillating atomic frequency ? (t), leading to multiple zero-transition points.

  16. Slow light of an amplitude modulated Gaussian pulse in electromagnetically induced transparency medium

    CERN Document Server

    Tang, Wenzhuo; Liu, Yu; Guo, Hong

    2009-01-01

    The slow light effects of an amplitude modulated Gaussian (AMG) pulse in a cesium atomic vapor cell are presented. In a single-$\\Lambda$ type electromagnetically induced transparency (EIT) medium, more severe distortion is observed for the AMG pulse than a Gaussian one. Using Fourier spectrum analysis, we find that it is the linear absorption of the medium that mainly causes the loss and distortion of the slowed pulse. Further, it is found that the dispersion determines the group velocities and causes an additional distortion of the AMG pulse due to its spectral distribution. Based on the transmission (absorption) spectrum, we propose a post-processing method to recover the shape and intensity of the slowed pulse. In addition, this method reveals a novel way to obtain the simultaneously slow and fast light of different spectral components of a single pulse.

  17. Decoding Finger Flexion using amplitude modulation from band-specific ECoG

    CERN Document Server

    Liang, Nanying

    2009-01-01

    EEG-BCIs have been well studied in the past decades and implemented into several famous applications, like P300 speller and wheelchair controller. However, these interfaces are indirect due to low spatial resolution of EEG. Recently, direct ECoG-BCIs attract intensive attention because ECoG provides a higher spatial resolution and signal quality. This makes possible localization of the source of neural signals with respect to certain brain functions. In this article, we present a realization of ECoG-BCIs for finger flexion prediction provided by BCI competition IV. Methods for finger flexion prediction including feature extraction and selection are provided in this article. Results show that the predicted finger movement is highly correlated with the true movement when we use band-specific amplitude modulation.

  18. Generation of nondiffracting quasi-circular polarization beams using an amplitude modulated phase hologram.

    Science.gov (United States)

    Yuan, G H; Wei, S B; Yuan, X-C

    2011-08-01

    We propose an approach to the generation of nondiffracting quasi-circularly polarized beams by a highly focusing azimuthally polarized beam using an amplitude modulated spiral phase hologram. Numerical verifications are implemented in the calculation of the electromagnetic fields and Poynting vector field near the focus based on the vector diffraction theory, and the polarization of the wavefront near the focal plane is analyzed in detail by calculating the Stokes polarization parameters. It is found that the electric field, magnetic field, and Poynting vector field can simultaneously be uniform and nondiverging over a relatively long axial range of ~7.23?. In the transverse plane, the ellipticity and azimuthal angle of the local polarization ellipse varies from point to point. No polarization singularity and phase singularity are found at the beam center, which makes the bright spot possible. PMID:21811334

  19. Effect of amplitude modulation of gravitational vibration on convective instability of reaction fronts in porous media

    Directory of Open Access Journals (Sweden)

    K. Allali

    2013-01-01

    Full Text Available This paper studies the influence of periodic and quasi-periodic amplitudemodulations of gravitational vibration on the convective instabilityof reaction fronts in porous media. Specifically, two cases of amplitudemodulation are investigated. In the first case, we consider that thefrequency ?2 of the amplitude modulation is either double or half thefrequency of the basic gravitational vibration ?1. In this case the modulatedgravitational vibration remains periodic. In the second case, weassume that the frequency ?2 is such that ?1 and ?2 are incommensuratewhich forces the gravitational vibration to be quasi-periodic. The modelconsidered in this study consists of the heat equation, the equation forthe depth of conversion and the equations of motion under the Darcylaw. The convective instability threshold is obtained. The linear stabilityanalysis of the steady-state solution is performed and the obtainedinterface problem is solved numerically.

  20. A coronagraph based on two spatial light modulators for active amplitude apodizing and phase corrections

    Science.gov (United States)

    Dou, Jiangpei; Ren, Deqing; Zhang, Xi; Zhu, Yongtian; Zhao, Gang; Wu, Zhen; Chen, Rui; Liu, Chengchao; Yang, Feng; Yang, Chao

    2014-08-01

    Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA) for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose, we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators (SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 ?/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.

  1. Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications

    Directory of Open Access Journals (Sweden)

    Sethakaset Ubolthip

    2005-01-01

    Full Text Available We propose a novel differential amplitude pulse-position modulation (DAPPM for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR. The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM depending on the number of amplitude levels and the maximum length of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about and more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM . When the number of bits per symbol is the same, PAM requires more power, and DH-PIM less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.

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

    OpenAIRE

    Hassan Farhan Rashag; Koh, S. P.; Chong, K. H.; Tiong, S. K.; Tan, Nadia M. L.; Abdalla, Ahmed N.

    2013-01-01

    Various aspects related to controlling induction motor are investigated. Direct torque control is an original high performance control strategy in the field of AC drive. In this proposed method, the control system is based on Space Vector Modulation (SVM), amplitude of voltage in direct- quadrature reference frame (d-q reference) and angle of stator flux. Amplitude of stator voltage is controlled by PI torque and PI flux controller. The stator flux angle is adjusted by rotor angular frequency...

  3. Responses of Medullary Lateral Line Units of the Goldfish, Carassius auratus, to Amplitude-Modulated Sinusoidal Wave Stimuli

    Directory of Open Access Journals (Sweden)

    Ramadan Ali

    2010-01-01

    Full Text Available This paper describes the responses of brainstem lateral line units in goldfish, Carassius auratus, to constant-amplitude and to amplitude-modulated sinusoidal water motions. If stimulated with constant-amplitude sinusoidal water motions, units responded with phasic (50% or with sustained (50% increases in dicharge rate. Based on isodisplacement curves, units preferred low (33?Hz, 12.5%, mid (50?Hz, 10% and 100?Hz, 30% or high (200?Hz, 47.5% frequencies. In most units, responses were weakly phase locked to the carrier frequency. However, at a carrier frequency of 50?Hz or 100?Hz, a substantial proportion of the units exhibited strong phase locking. If stimulated with amplitude-modulated water motions, units responded with a burst of discharge to each modulation cycle, that is, units phase locked to the amplitude modulation frequency. Response properties of brainstem units were in many respects comparable to those of midbrain units, suggesting that they emerge first in the lateral line brainstem.

  4. Immunological effects of amplitude-modulated radio frequency radiation: B lymphocyte capping

    Energy Technology Data Exchange (ETDEWEB)

    Sultan, M.F.; Cain, C.A.; Tompkins, W.A.

    1983-01-01

    B lymphocytes collected from normal ICR Swiss mouse spleens were exposed in vitro in a Crawford cell to 147-MHz radiofrequency (RF) radiation, amplitude modulated by a 9-, 16-, or 60-Hz sine wave. The power densities ranged between 0.11 and 48 mW/cm2. The irradiated samples and the controls were maintained at 37 degrees C or 42 degrees C, with temperature variations less than 0.1 degrees C. Immediately after a 30-minute exposure, the distribution of antigen-antibody (Ag-Ab) complexes on the cell surface was evaluated at 37 degrees C by immunofluorescence. Under normal conditions (37 degrees C, no RF), Ag-Ab complexes are regrouped into a polar cap by an energy-dependent process. Our results demonstrate that the irradiated cells and the nonirradiated controls capped Ag-Ab complexes equally well after exposure at 37 degrees C. Capping was equally inhibited at 42 degrees C in both the controls and irradiated cells. No statistically significant differences in capping were observed between the RF-exposed and control samples at any of the modulation frequencies and power densities employed as long as both preparations were maintained at the same temperature.

  5. [Auditory steady-state response to sinusoidally amplitude-modulated tones. Second report: investigation of response in the sleeping state].

    Science.gov (United States)

    Umegaki, Y

    1995-03-01

    The auditory steady state response (SSR) elicited by a sinusoidally amplitude-modulated (SAM) tone may be an important technique in objective audiometry, which provides frequency-specific information. This response is affected the state of arousal of the subject. An effect of sleep on the amplitude of this response has been observed by a number of previous investigators. Since young children must usually be sedated to carry out evoked potential testing, the effects of sleep on this response are a crucial factor limiting clinical applicability. The basic characteristics of SSR elicited by a 500 Hz SAM tone were studied in 21 adults with normal hearing during sleep. The responses while sleeping were compared with the responses in the awake state. The responses to 2048 stimuli were averaged with the analysis time set at 102.4 ms, and responses were judged by passing the waveforms through a 20-100 Hz digital filter. The same technique was performed in 25 infants (2 months-2 years 9 months) evaluated as having normal hearing. The results obtained are summarized as follows: The amplitude of the response while sleeping was approximately half the amplitude in the awake state. Responses with a modulation frequency of 70Hz, however, showed a persistent decrease in 71.0%, suggesting a trend different from that seen at a modulation frequency of less than 70Hz. The effect of modulation frequency on response amplitude was almost the same for the sleeping state and the awake state. Even during sleep, the response amplitude was maximal at modulation frequencies of 20, 30 and 40Hz, and there was no significant difference between the values at 20Hz -40Hz. The latency of the response was measured by the Diamond method, and the results showed that latency is significantly prolonged while sleeping (p < 0.01). The response threshold at the 500Hz SAM tone (modulation rate 40Hz, modulation depth 90%) was 8.5dBnHL when awake and 13.9dBnHL during sleep. The rise in threshold as a result of sleep was no more than about 5dB. In infants, the response amplitude at a modulation frequency of 20Hz was maximal, and amplitude at the 40Hz was significantly smaller (p < 0.01). Latency measured by the Diamond method in infants was 12.8ms. Thus, a difference from the response in adults was confirmed. Comparisons were made between the responses of infants under 1 year of age and infants over 1 year of age to confirm changes in response according to age. PMID:7738707

  6. Amplitude modulation of charge-density-wave domains in 1T-TaS2 at 300 K

    International Nuclear Information System (INIS)

    Measurements of the charge-density-wave (CDW) amplitude modulation in 1T-TaS2 at room temperature have been made using a scanning tunneling microscope (STM) operating in the constant current mode. The amplitude profiles are in good agreement with the profile predicated by the CDW domain model of Nakanishi and Shiba. Interference effects between the atomic and CDW lattices have been analyzed and do not modify these profiles significantly. They represent the true CDW amplitude variation connected with the CDW domain structure

  7. Instantaneous amplitude and angular frequency modulation of light in time-dependent PT-symmetric optical potentials

    CERN Document Server

    Hayrapetyan, Armen G; Goette, Joerg B

    2015-01-01

    We study the impact of spatially homogeneous yet non-stationary PT-symmetric dielectric permittivity in dynamical and spectral properties of light. For such a time-reversal optical system, we analytically construct the instantaneous amplitude and angular frequency of waves within the framework of Maxwell's equations and demonstrate PT modulations of light amplification and attenuation associated with the well-defined regions of gain and loss, respectively. Particularly strong enhancement of amplitude modulation towards the loss domain is shown to be expected depending on fine tuning of parameters of the complex permittivity profile. Moreover, we predict the split of extrema of angular frequency modulation and demonstrate the shrinkage of the modulation period. Our theory can be extended for investigating similar time-dependent effects with matter and acoustic waves in PT-symmetric structures.

  8. Aged-Related Loss of Temporal Processing: Altered Responses to Amplitude Modulated Tones in Rat Dorsal Cochlear Nucleus

    OpenAIRE

    Schatteman, Tracy A.; Hughes, Larry F.; Caspary, Donald M.

    2008-01-01

    Loss of temporal processing is characteristic of age-related loss of speech understanding observed in the elderly. Inhibitory glycinergic circuits provide input onto dorsal cochlear nucleus (DCN) projection neurons which likely serve to modulate excitatory responses to time-varying complex acoustic signals. The present study sought to test the hypothesis that age-related loss of inhibition would compromise the ability of output neurons to encode sinusoidally amplitude modulated (SAM) tones. E...

  9. On the relevance of the atomic-scale contact potential difference by Amplitude modulation- and Frequency modulation-Kelvin probe force microscopy

    OpenAIRE

    Nony, Laurent; Bocquet, Franck; Loppacher, Christian; Glatzel, Thilo

    2009-01-01

    The influence of short-range electrostatic forces on the measured local Contact Potential Difference (CPD) by means of Amplitude Modulation- and Frequency Modulation-Kelvin Probe Force Microscopy (AM- and FM-KPFM) is discussed on the base of numeric and analytic descriptions of both methods. The goal of this work is to help interpreting recent experimental results reporting atomically-resolved CPD images, in particular on bulk insulating samples. The discussion is carried out on the base of s...

  10. VCSEL-Based DWDM PON With 4 BIT/S/HZ Spectral Efficiency Using Carrierless Amplitude Phase Modulation

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto; Wieckowski, Marcin

    2011-01-01

    We experimental demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs.

  11. Recovery of Lunar Surface Access Module Residual and Reserve Propellants

    Science.gov (United States)

    Notardonato, William U.

    2007-01-01

    The Vision for Space Exploration calls for human exploration of the lunar surface in the 2020 timeframe. Sustained human exploration of the lunar surface will require supply, storage, and distribution of consumables for a variety of mission elements. These elements include propulsion systems for ascent and descent stages, life support for habitats and extra-vehicular activity, and reactants for power systems. NASA KSC has been tasked to develop technologies and strategies for consumables transfer for lunar exploration as part of the Exploration Technology Development Program. This paper will investigate details of operational concepts to scavenge residual propellants from the lunar descent propulsion system. Predictions on the mass of residuals and reserves are made. Estimates of heat transfer and boiloff rates are calculated and transient tank thermodynamic issues post-engine cutoff are modeled. Recovery and storage options including cryogenic liquid, vapor and water are discussed, and possible reuse of LSAM assets is presented.

  12. Aharonov–Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings

    International Nuclear Information System (INIS)

    Low-temperature Aharonov–Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms. (paper)

  13. Geometry distortions of nanostructure edges scanned with amplitude-modulated atomic force microscopes

    International Nuclear Information System (INIS)

    In nanotechnology and semiconductor fabrication geometry parameters of nanostructures such as curvatures and side wall angles are of increasing relevance with decreasing feature sizes. The atomic force microscope (AFM) is still one of the main measurement tools employed to investigate topographical parameters. It is generally operated in oscillation mode in order to avoid wear or damage of the probe. As imaging instruments deliver data that are influenced by the probing process, appropriate reconstruction processes are needed. This paper shows a significant contrast of the phase lag of the probe of an amplitude-modulated AFM (AM-AFM) and its driving force at the edge transition of nanostructures with a high aspect ratio. A simulation model reveals the relation between interaction forces and the observed phase behavior. It illustrates how the equilibrium positions of an oscillating probe differ from those of a sample geometry that is purely dilated by static probe tip contact. We show that AFM measurements in oscillation mode deliver a distorted topography image and that the greater the distortion the more energy dissipation is involved. An understanding of the distortion mechanism forms the basis for the development of reconstruction strategies. (paper)

  14. Photosynthesis assessment in microphytobenthos using conventional and imaging pulse amplitude modulation fluorometry.

    Science.gov (United States)

    Vieira, Sónia; Ribeiro, Lourenço; Jesus, Bruno; Cartaxana, Paulo; da Silva, Jorge Marques

    2013-01-01

    Imaging pulse amplitude modulated (Imaging-PAM) fluorometry is a breakthrough in the study of spatial heterogeneity of photosynthetic assemblages. However, Imaging and conventional PAM uses a different technology, making comparisons between these techniques doubtful. Thereby, photosynthetic processes were comparatively assessed using conventional (Junior PAM and PAM 101) and Imaging-PAM on intertidal microphytobenthos (MPB; mud and sand) and on cork oak leaves. Lower values of ? (initial slope of the rETR, relative photosynthetic electron transport rate) vs E (incident photosynthetic active radiation) curve), ETR(max) (maximum relative ETR), E(k) (light saturation parameter) and F(v)/F(m) (maximum quantum efficiency of photosystem II of dark-adapted samples) were obtained using the Imaging-PAM. The level of discrepancy between conventional and Imaging-PAM systems was dependent on the type of sample, being more pronounced for MPB muddy sediments. This may be explained by differences in the depth integration of the fluorescence signal related to the thickness of the photosynthetic layer and in the light attenuation coefficients of downwelling irradiance. An additional relevant parameter is the taxonomic composition of the MPB, as cyanobacteria present in sandy sediments rendered different results with red and blue excitation light fluorometers. These findings emphasize the caution needed when interpreting chlorophyll fluorescence data of MPB communities. PMID:22891982

  15. Frequency-selective manipulation of spin waves: micromagnetic texture as amplitude valve and mode modulator

    Science.gov (United States)

    Xing, Xiangjun; Jin, Qingli; Li, Shuwei

    2015-02-01

    Spin–wave devices are regarded as one of the most promising candidates for future computation and data processing. How to manipulate spin–wave propagation is a key issue in realizing the functionality of these of devices. The existing manipulation methods have serious drawbacks for constructing practical spin–wave devices. Here, we propose an approach to harness the amplitude and mode excitation of traveling spin waves by introducing unique micromagnetic textures in a permalloy waveguide directly exchange-coupled to a pair of cobalt nanomagnets. We demonstrate that the imprinted micromagnetic textures, i.e., the 360° domain wall and magnetic buckle, which play different roles in spin–wave manipulation, can be interchanged with each other repeatedly by using a sequence of homogeneous magnetic fields. Moreover, the suggested architecture could easily be tailored to implement fundamental logic-NOT operation. In light of the internal-field profile of the micromagnetic textures, speculation is offered concerning the physical origin underlying the observed spin–wave modulation phenomena.

  16. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    Science.gov (United States)

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging". PMID:25047226

  17. Wavelet analysis of pulse-amplitude-modulated chlorophyll fluorescence for differentiation of plant samples.

    Science.gov (United States)

    Guo, Ya; Zhou, Yesen; Tan, Jinglu

    2015-04-01

    Pulse-amplitude-modulated (PAM) chlorophyll fluorescence (ChlF) from photosystem II (PSII) of plants has been routinely measured for the analysis of photosynthesis and environmental changes. PAM ChlF from PSII is non-stationary and has time-varying frequency characteristics; however, existing analysis of PAM ChlF has been limited to selected characteristic values in the time domain. Wavelet transform is recognized as an efficient tool for analyzing non-stationary signals. In this research, an attempt was made to analyze PAM ChlF through wavelet transform. Features of PAM ChlF signals were computed from wavelet decomposition to classify two tree species and to detect chilling and detachment stresses. The wavelet-based features were compared with the commonly-used maximal PSII efficiency Fv/Fm. Both the wavelet-based features and Fv/Fm could effectively classify two tree species, but the former showed superiority than the latter in detecting the stresses. Wavelet transform revealed chilling stress earlier than Fv/Fm and detected detachment stress Fv/Fm failed to show. The results show that wavelet transform is a useful technique for analysis of PAM ChlF. PMID:25665719

  18. A sodium-activated potassium channel supports high-frequency firing and reduces energetic costs during rapid modulations of action potential amplitude

    OpenAIRE

    Markham, Michael R.; Kaczmarek, Leonard K.; Zakon, Harold H.

    2013-01-01

    We investigated the ionic mechanisms that allow dynamic regulation of action potential (AP) amplitude as a means of regulating energetic costs of AP signaling. Weakly electric fish generate an electric organ discharge (EOD) by summing the APs of their electric organ cells (electrocytes). Some electric fish increase AP amplitude during active periods or social interactions and decrease AP amplitude when inactive, regulated by melanocortin peptide hormones. This modulates signal amplitude and c...

  19. Growth and saturation of large amplitude self-modulated wakefield in 60 TW laser plasma and possible electron acceleration

    International Nuclear Information System (INIS)

    A 25 J -1.053 ?m pulse in 0.45 ps (a0= 2.2) was injected into a gas jet. This excited a large amplitude self-modulated wakefield. By increasing the pulse length from 0.45 to to 1.2 ps, the wakefield grew close to the wave-breaking limit, which sustained a 350 ± 150 GV/m acceleration field over a 1 mm dephasing distance along the laser axis in a plasma with density 2 x 1019 cm-3. This resulted in electrons accelerated to 300 MeV. The amplitude saturation of the wakefield is explained by a pump depletion effect to the large amplitude forward Raman instability. The Petawatt Laser is completed, which will be used to accelerate electrons above one GeV

  20. Effect of amplitude-modulated 147 MHz radiofrequency radiation on calcium ion efflux from avian brain tissue

    International Nuclear Information System (INIS)

    Cerebral cortex tissue slices and cerebral hemispheres prepared from Gallus domesticus chicks were exposed to 147 MHz radiofrequency radiation, amplitude modulated at 16 Hz and applied at a power density of 0.75 mW/cm2, to determine the effect of such exposure of 45Ca2+ efflux from the avian brain tissue. Statistical analysis of these data demonstrates that such exposure has no significant effect on 45Ca2+ efflux

  1. M-ARRAY QUADRATURE AMPLITUDE MODULATION WIRELESS SENSOR NETWORK MODULATOR RELIABILITY AND ACCURACY ANALYZE IN CIVIL SHM

    Directory of Open Access Journals (Sweden)

    Mohammud Ershadul Haque

    2013-01-01

    Full Text Available Wireless Sensor Network (WSN is the new invention applying for assessment the damage of the historical or high rise civil building structural health. Technical challenges affecting deployment of wireless sensor network including the range of the transmission problem, low data transmission rate of the existing SHM strategies. The most vital factor of SHM wireless sensor systems is the modulator accuracy and reliability that qualify the wireless communication system to assess large building structure health Information. The objective of this article is to provide solution to measure both reliability and accuracy of the wireless sensor network modulator. we computed M-array QAM modulator BER and compare the simulation result with theoretical to find out optimum modulation technique for transmission System with considering maximum data rate, AWGN channel and also measured modulator accuracy based on ZigBee by computing M-array modulator Error Vector Magnitude (EVM to quantify the transmitter quality.

  2. Sensitivity evaluation of the green alga Chlamydomonas reinhardtii to uranium by pulse amplitude modulated (PAM) fluorometry

    Energy Technology Data Exchange (ETDEWEB)

    Herlory, Olivier, E-mail: olivier.herlory@gmail.com [IRSN-Laboratoire d’Ecotoxicologie des Radionucléides, Centre de Cadarache, BP3, 13115 Saint Paul lez Durance (France); Bonzom, Jean-Marc, E-mail: jean-marc.bonzom@irsn.fr [IRSN-Laboratoire d’Ecotoxicologie des Radionucléides, Centre de Cadarache, BP3, 13115 Saint Paul lez Durance (France); Gilbin, Rodolphe, E-mail: rodolphe.gilbin@irsn.fr [IRSN-Laboratoire de Biogéochimie, Biodisponibilité et Transferts des Radionucléides, Centre de Cadarache, BP3, 13115 Saint Paul lez Durance (France)

    2013-09-15

    Highlights: •Our study addressed the toxicity thresholds of uranium on microalgae using PAM fluorometry. •The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium. •Uranium impaired the electron flux between the photosystems until almost complete inhibition. •Non-photochemical quenching was identified as the most sensitive fluorescence parameter. •PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response. -- Abstract: Although ecotoxicological studies tend to address the toxicity thresholds of uranium in freshwaters, there is a lack of information on the effects of the metal on physiological processes, particularly in aquatic plants. Knowing that uranium alters photosynthesis via impairment of the water photo-oxidation process, we determined whether pulse amplitude modulated (PAM) fluorometry was a relevant tool for assessing the impact of uranium on the green alga Chlamydomonas reinhardtii and investigated how and to what extent uranium hampered photosynthetic performance. Photosynthetic activity and quenching were assessed from fluorescence induction curves generated by PAM fluorometry, after 1 and 5 h of uranium exposure in controlled conditions. The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium, through alteration of the water photo-oxidation process as revealed by F{sub 0}/F{sub v}. Limiting re-oxidation of the plastoquinone pool, uranium impaired the electron flux between the photosystems until almost complete inhibition of the PSII quantum efficiency (F{sup ?}{sub q}/F{sup ?}{sub m}, EC{sub 50} = 303 ± 64 ?g U L{sup ?1} after 5 h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC{sub 50} = 142 ± 98 ?g U L{sup ?1} after 5 h of exposure), indicating that light energy not used in photochemistry was dissipated in non-radiative processes. It was shown that parameters which stemmed from fluorescence induction kinetics are valuable indicators for evaluating the impact of uranium on PSII in green algae. PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response to uranium in microalgae.

  3. Tuning in on Cepheids: Radial velocity amplitude modulations. A source of systematic uncertainty for Baade-Wesselink distances

    CERN Document Server

    Anderson, Richard I

    2014-01-01

    [Abridged] I report the discovery of modulations in radial velocity (RV) curves of four Galactic classical Cepheids and investigate their impact as a systematic uncertainty for Baade-Wesselink distances. Highly precise Doppler measurements were obtained using the Coralie high-resolution spectrograph since 2011. Particular care was taken to sample all phase points in order to very accurately trace the RV curve during multiple epochs and to search for differences in linear radius variations derived from observations obtained at different epochs. Different timescales are sampled, ranging from cycle-to-cycle to months and years. The unprecedented combination of excellent phase coverage obtained during multiple epochs and high precision enabled the discovery of significant modulation in the RV curves of the short-period s-Cepheids QZ Normae and V335 Puppis, as well as the long-period fundamental mode Cepheids l Carinae and RS Puppis. The modulations manifest as shape and amplitude variations that vary smoothly on ...

  4. Dynamic range enhancement and amplitude regeneration in single pump fibre optic parametric amplifiers using DPSK modulation

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Lorenzen, Michael Rodas

    2008-01-01

    Input power dynamic range enhancement and amplitude regeneration of highly distorted signals are demonstrated experimentally for 40 Gbit/s RZ-DPSK in a single-pump fibre parametric amplifier with 22 dB smallsignal gain.

  5. The relationship between geophysical conditions and ELF amplitude in modulated heating experiments at HAARP: Modeling and experimental results

    Science.gov (United States)

    Jin, G.; Spasojevic, M.; Cohen, M. B.; Inan, U. S.; Lehtinen, N. G.

    2011-07-01

    Experiments for generating extremely low frequency (ELF) radio waves using modulated HF heating of the auroral ionosphere have been conducted and refined at the High Frequency Active Auroral Research Program (HAARP) facility at Gakona, Alaska. Because this technique is dependent on strength of the naturally generated electrojet current system, the amplitude of the generated ELF changes with geophysical conditions. Past work has shown that electrojet current strength as measured by magnetometers often correlates with generated ELF amplitude, but there are periods of poor or negative correlation. We attempt to use additional diagnostics from a radar, riometer, ionosonde, and magnetometer chain to understand how ionospheric conditions affect ELF generation. We then present the results of a statistical model that shows that ELF amplitude is roughly proportional to magnetometer measurements for a fixed value of riometer absorption and that the proportionality constant decreases as riometer absorption increases. Theoretical simulations of modulated heating are conducted for a variety of ionospheric density profiles to verify that denser profiles result in smaller gains for ELF generation as a function of electrojet current at a given electric field.

  6. Steady-state MEG responses elicited by a sequence of amplitude-modulated short tones of different carrier frequencies.

    Science.gov (United States)

    Kuriki, Shinya; Kobayashi, Yusuke; Kobayashi, Takanari; Tanaka, Keita; Uchikawa, Yoshinori

    2013-02-01

    The auditory steady-state response (ASSR) is a weak potential or magnetic response elicited by periodic acoustic stimuli with a maximum response at about a 40-Hz periodicity. In most previous studies using amplitude-modulated (AM) tones of stimulus sound, long lasting tones of more than 10 s in length were used. However, characteristics of the ASSR elicited by short AM tones have remained unclear. In this study, we examined magnetoencephalographic (MEG) ASSR using a sequence of sinusoidal AM tones of 0.78 s in length with various tone frequencies of 440-990 Hz in about one octave variation. It was found that the amplitude of the ASSR was invariant with tone frequencies when the level of sound pressure was adjusted along an equal-loudness curve. The amplitude also did not depend on the existence of preceding tone or difference in frequency of the preceding tone. When the sound level of AM tones was changed with tone frequencies in the same range of 440-990 Hz, the amplitude of ASSR varied in a proportional manner to the sound level. These characteristics are favorable for the use of ASSR in studying temporal processing of auditory information in the auditory cortex. The lack of adaptation in the ASSR elicited by a sequence of short tones may be ascribed to the neural activity of widely accepted generator of magnetic ASSR in the primary auditory cortex. PMID:23174483

  7. A simple and reliable technique to characterize amplitude to phase modulation distortion for high-frequency amplifiers and nonlinear devices.

    Science.gov (United States)

    Jauregui, Rigoberto; Portilla, Joaquin; Reynoso-Hernández, J A; Hirata-Flores, F I

    2013-08-01

    This paper presents a simple and reliable measurement system for characterizing the amplitude to phase modulation (AM-PM) characteristics of high frequency amplifiers and nonlinear devices. The AM-PM measurement system is based on a null detector implemented with a double balanced mixer, and requires a voltmeter and a calibrated phase shifter. A 12 W class A radio frequency power amplifier has been designed using a GaN transistor, and the AM-PM has been measured using both the method proposed in this work and the classical method with a calibrated vector network analyzer. A good correlation between both methods is observed, which validates the proposed method. PMID:24007089

  8. Travel Time Shifts due to Amplitude Modulation in Time-Distance Helioseismology

    OpenAIRE

    Nigam, R.; Kosovichev, A. G.

    2009-01-01

    Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times has not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is ar...

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

    DEFF Research Database (Denmark)

    Isaeva, Olga B.; Kuznetsov, Sergey P.

    2011-01-01

    The paper proposes an approach to constructing feasible examples of dynamical systems with hyperbolic chaotic attractors based on the successive transfer of excitation between two pairs of self-oscillators that are alternately active. An angular variable that measures the relations of the current amplitudes for the two oscillators of each pair undergoes a transformation in accordance with the expanding circle map during each cycle of the process. We start with equations describing the dynamics in terms of complex or real amplitudes and then examine two models based on van der Pol oscillators. One model corresponds to the situation of equality of natural frequencies of the partial oscillators, and another to a nonresonant ratio of the oscillation frequencies relating to each of the two pairs. Dynamics of all models are illustrated with diagrams indicating the transformation of the angular variables, portraits of attractors, Lyapunov exponents, etc. The uniformly hyperbolic nature of the attractor in the stroboscopic Poincare map is confirmed for a real-amplitude version of the equations by computations of statistical distribution of angles between stable and unstable manifolds at a representative set of points on the attractor. In other versions of the equations the attractors relate presumably to the partially hyperbolic class.

  10. Current-driven Langmuir oscillations and amplitude modulations—Another view on electron beam-plasma interaction

    Science.gov (United States)

    Sauer, K.; Sydora, R. D.

    2015-01-01

    origin of Langmuir amplitude modulations and harmonic waves observed in the solar wind and in planetary foreshock regions is investigated in beam plasmas where the saturation process of the beam instability is accompanied with the formation of a plateau distribution. This saturated state represents a current which is shown to drive homogeneous electric field oscillations at the plasma frequency. This simple mechanism has been ignored in most numerical studies based on Vlasov or particle-in-cell simulations because of the use of the Poisson equation which is not suitable to describe the mechanism of current drive in plasmas with immobile ions; instead, Ampere's law must be used. A simple fluid description of stable plateau plasmas, coupled with Ampere's law, is applied to illustrate the basic elements of current-driven Langmuir oscillations. If beam-generated Langmuir/electron-acoustic waves with frequencies above or below the plasma frequency are simultaneously present, beating of both wave modes leads to Langmuir amplitude modulations, thus providing an alternative to parametric decay. Furthermore, very important implications of our studies (presented separately) concern the electrostatic and electromagnetic second harmonic generation by nonlinear interaction of Langmuir oscillations with finite wave number modes which are driven by the plateau current as well.

  11. Multisensory interaction in vibrotactile detection and discrimination of amplitude modulation : insights from expert MFS surgeons and naive participants

    DEFF Research Database (Denmark)

    Teodorescu, Kinneret; Bouchigny, Sylvain

    2011-01-01

    Perception of vibration during drilling demands integration of haptic and auditory information with force information. In this study we explored the ability to detect and discriminate changes in vibrotactile stimuli amplitude based either on purely haptic feedback or together with congruent synthesized auditory cues in groups of naive subjects and expert surgeons. Our results point toward the complex influence of multimodal experience during vibration perception. First, in naive subjects, we showed that detection and discrimination of amplitude change in complex vibro-tactile stimulus is selectively sensitive to combination of modality and previous experience. In the domain of discrimination, our results suggest that bi-modal performance is always better than uni-modal performance regardless of order of experience. Second, experiments with expert surgeons revealed that expertise in complex skill of maxilla-facial surgery strongly relies on enhanced touch perception, as measured in reaction times and discrimination ability in bi-modal vibro-auditory conditions. These observations suggest that acquisition of mandibular surgery skill has brought to an enhanced representation of vibro-tactile modulations in relevant stimuli ranges. Altogether, our results provide basis to assume that during acquisition of mandibular drilling skill, trainees may benefit from training of relevant basic aspects of touch perception - sensitivity to vibration and accompanying modulations of sound.

  12. Multisensory interaction in vibrotactile detection and discrimination of amplitude modulation: insights from expert MFS surgeons and naive participants

    Directory of Open Access Journals (Sweden)

    Korman Maria

    2011-12-01

    Full Text Available Perception of vibration during drilling demands integration of haptic and auditory information with force information. In this study we explored the ability to detect and discriminate changes in vibrotactile stimuli amplitude based either on purely haptic feedback or together with congruent synthesized auditory cues in groups of naive subjects and expert surgeons. Our results point toward the complex influence of multimodal experience during vibration perception. First, in naive subjects, we showed that detection and discrimination of amplitude change in complex vibro-tactile stimulus is selectively sensitive to combination of modality and previous experience. In the domain of discrimination, our results suggest that bi-modal performance is always better than uni-modal performance regardless of order of experience. Second, experiments with expert surgeons revealed that expertise in complex skill of maxilla-facial surgery strongly relies on enhanced touch perception, as measured in reaction times and discrimination ability in bi-modal vibro-auditory conditions. These observations suggest that acquisition of mandibular surgery skill has brought to an enhanced representation of vibro-tactile modulations in relevant stimuli ranges. Altogether, our results provide basis to assume that during acquisition of mandibular drilling skill, trainees may benefit from training of relevant basic aspects of touch perception - sensitivity to vibration and accompanying modulations of sound.

  13. Risk exposure to extremely low frequencies and to amplitude modulated radio frequencies

    International Nuclear Information System (INIS)

    Human B cells exposure for 72 hrs to extremely low electromagnetic field or modulated radiofrequency resulted at change of the plasma membrane morphology, resulting at loss of microvilli. Together with the change in morphology we could detected a different actin distribution and natural killer activity

  14. Comparison of carrierless amplitude-phase (CAP) and discrete multitone (DMT) modulation

    DEFF Research Database (Denmark)

    Othman, M. B.; Pham, Tien-Thang

    2014-01-01

    We compare the transmission of 1.25 Gb/s CAP-16 and 909.2 Mb/s 16-QAM-DMT modulation formats over 2.4 km of MMF with 850 nm DM-CSELs. CAP displays 0.7-1.1 dB better sensitivity than DMT in this experiment.

  15. Frequency and Amplitude Modulation Have Different Effects on the Percepts Elicited by Retinal Stimulation

    OpenAIRE

    Nanduri, Devyani; Fine, Ione; Horsager, Alan; Boynton, Geoffrey M.; Humayun, Mark S.; Greenberg, Robert J.; Weiland, James D.

    2012-01-01

    To restore functional form vision, epiretinal prostheses have been implanted in blind human subjects to electrically elicit percepts. These findings suggest that frequency modulation may be the best way to produce percepts that range widely in brightness while minimizing loss of spatial resolution.

  16. Amplitude modulation for the Swift-Hohenberg and Kuramoto-Sivashinski equations

    Science.gov (United States)

    Kirkinis, Eleftherios; O'Malley, Robert E.

    2014-12-01

    Employing a harmonic balance technique inspired from the methods of Renormalization Group and Multiple Scales [R. E. O'Malley, Jr. and E. Kirkinis. "A combined renormalization group-multiple scale method for singularly perturbed problems," Stud. Appl. Math. 124(4), 383-410, (2010)], we derive the amplitude equations for the Swift-Hohenberg and Kuramoto-Sivashinski equations to arbitrary order in the context of roll patterns. This new and straightforward derivation improves previous attempts and can be carried-out with symbolic computation that minimizes effort and avoids error.

  17. A bandwidth compressive modulation system using multi-amplitude minimum shift keying /MAMSK/. [for spacecraft communication

    Science.gov (United States)

    Weber, W. J., III; Stanton, P. H.; Sumida, J. T.

    1978-01-01

    A bandwidth compressive modem making use of multi-amplitude minimum shift keying (MAMSK) has been designed and implemented in a laboratory environment at microwave frequencies. This system achieves a substantial bandwidth reduction over binary PSK and operates within 0.5 dB of theoretical performance. A number of easily implemented microwave transmitters have been designed to generate the required set of 16 signals. The receiver has been designed to work at 1 Mbit/s and contains the necessary phase tracking, AGC, and symbol synchronization loops as well as a lock detector, SNR estimator and provisions for differential decoding. This paper describes this entire system and presents the experimental results.

  18. Self-amplitude and self-phase modulation of the charcoal mode-locked erbium-doped fiber lasers.

    Science.gov (United States)

    Lin, Yung-Hsiang; Lo, Jui-Yung; Tseng, Wei-Hsuan; Wu, Chih-I; Lin, Gong-Ru

    2013-10-21

    With the intra-cavity nano-scale charcoal powder based saturable absorber, the 455-fs passive mode-locking of an L-band erbium-doped fiber laser (EDFL) is demonstrated. The size reduction of charcoal nano-particle is implemented with a simple imprinting-exfoliation-wiping method, which assists to increase the transmittance up to 0.91 with corresponding modulation depth of 26%. By detuning the power gain from 17 to 21 dB and cavity dispersion from -0.004 to -0.156 ps² of the EDFL, the shortening of mode-locked pulsewidth from picosecond to sub-picosecond by the transformation of the pulse forming mechanism from self-amplitude modulation (SAM) to the combining effect of self-phase modulation (SPM) and group delay dispersion (GDD) is observed. A narrower spectrum with 3-dB linewidth of 1.83-nm is in the SAM case, whereas the spectral linewidth broadens to 5.86 nm with significant Kelly sideband pair can be observed if the EDFL enters into the SPM regime. The mode-locking mechanism transferred from SAM to SPM/GDD dominates the pulse shortening procedure in the EDFL, whereas the intrinsic defects in charcoal nano-particle only affect the pulse formation at initial stage. The minor role of the saturable absorber played in the EDFL cavity with strongest SPM is observed. PMID:24150360

  19. Amplitude-modulation mechanism for designing long-focal-depth cylindrical microlenses with a uniform axial intensity profile

    Science.gov (United States)

    Ye, Jia-Sheng; Mei, Guo-Ai; Zhang, Yan

    2012-10-01

    Although the long-focal-depth (LFD) function of cylindrical microlenses was previously realized by the phase modulation method, however, there still has no report of obtaining a uniform axial intensity distribution through the pure phase modulation mechanism. In this paper, the amplitude modulation mechanism is proposed for designing LFD cylindrical microlenses. An apodized window function of the incident light is used to suppress the axial intensity oscillations, so that a uniform axial intensity profile is achieved. Rigorous electromagnetic theory and the boundary element method are applied to analyzing focal performance of the designed cylindrical microlenses. Through replacing the incident plane wave with a two dimensional Bessel beam, numerical results demonstrate that the designed cylindrical microlens not only holds an LFD property, but also maintains a uniform axial intensity distribution as we expected. Moreover, the designed LFD cylindrical microlens has a high diffraction efficiency on the real focal plane. It is believed that the designed LFD cylindrical microlens with a uniform axial intensity profile should have wide application prospects in many micro optics systems.

  20. Rhythmic control of mRNA stability modulates circadian amplitude of mouse Period3 mRNA.

    Science.gov (United States)

    Kim, Sung-Hoon; Lee, Kyung-Ha; Kim, Do-Yeon; Kwak, Eunyee; Kim, Seunghwan; Kim, Kyong-Tai

    2015-03-01

    The daily oscillations observed in most living organisms are endogenously generated with a period of 24 h, and the underlying structure of periodic oscillation is an autoregulatory transcription-translation feedback loop. The mechanisms of untranslated region (UTR)-mediated post-transcriptional regulation (e.g., mRNA degradation and internal ribosomal entry site (IRES)-mediated translation) have been suggested to fine-tune the expression of clock genes. Mouse Period3 (mPer3) is one of the paralogs of Period gene and its function is important in peripheral clocks and sleep physiology. mPer3 mRNA displays a circadian oscillation as well as a circadian phase-dependent stability, while the stability regulators still remain unknown. In this study, we identify three proteins - heterogeneous nuclear ribonucleoprotein (hnRNP) K, polypyrimidine tract-binding protein (PTB), and hnRNP D - that bind to mPer3 mRNA 3'-UTR. We show that hnRNP K is a stabilizer that increases the amplitude of circadian mPer3 mRNA oscillation and hnRNP D is a destabilizer that decreases it, while PTB exhibits no effect on mPer3 mRNA expression. Our experiments describe their cytoplasmic roles for the mRNA stability regulation and the circadian amplitude formation. Moreover, our mathematical model suggests a mechanism through which post-transcriptional mRNA stability modulation provides not only the flexibility of oscillation amplitude, but also the robustness of the period and the phase for circadian mPer3 expression. Mouse Period3 (mPer3) is one of well-known clock genes. We identified three 3'-UTR-binding proteins that modulate the mRNA stability, and they influenced to the amplitude of circadian mPer3 mRNA oscillation. Our mathematical model not only showed the relationship between mRNA stability and its oscillation profile but provided the molecular mechanism for the robustness of the period and the phase in circadian oscillation. hnK, heterogeneous nuclear ribonucleoprotein (hnRNP) K; hnD, hnRNP D; PTB, polypyrimidine tract-binding protein. PMID:25581122

  1. Sensitivity of neurons in the auditory midbrain of the grassfrog to temporal characteristics of sound. II. Stimulation with amplitude modulated sound.

    Science.gov (United States)

    Epping, W J; Eggermont, J J

    1986-01-01

    The coding of fine-temporal structure of sound, especially of frequency of amplitude modulation, was investigated on the single-unit level in the auditory midbrain of the grassfrog. As stimuli sinusoidally amplitude modulated sound bursts and continuous sound with low-pass Gaussian noise amplitude modulation have been used. Both tonal and wideband noise carriers have been applied. The response to sinusoidally amplitude modulated sound bursts was studied in two aspects focussing on two types of possible codes: a rate code and a synchrony code. From the iso-intensity rate histogram five basic average response characteristics as function of modulation frequency have been observed: low-pass, band-pass, high-pass, bimodal and non-selective types. The synchronization capability, expressed in a synchronization index, was non-significant for 38% of the units and a low-pass function of modulation frequency for most of the other units. The stimulus-response relation to noise amplitude modulated sound was investigated by a non-linear system theoretical approach. On the basis of first- and second-order Wiener-Volterra kernels possible neural mechanisms accounting for temporal selectivity were obtained. About one quarter of the units had response characteristics that were invariant to changes in sound pressure level and spectral content of the carrier. These units may function as feature detectors of fine-temporal structure of sound. The spectro-temporal sensitivity range of the auditory midbrain of the grassfrog appeared not to be restricted to and showed no preference for the spectro-temporal characteristics of the ensemble of conspecific calls. Comparison of response characteristics to periodic click trains as studied in the companion paper (Epping and Eggermont, 1986) and sinusoidally amplitude modulated sound bursts revealed that the observed temporal sensitivity is due to a combination of sensitivities to sound periodicity and pulse duration. It was found that for most units the first-order kernels for Gaussian amplitude modulated stimuli and Poisson distributed click stimuli were alike. In contrast second-order kernels for the Gaussian amplitude modulated stimuli often represented only static non-linearities, while second-order kernels for Poisson distributed clicks (Epping and Eggermont, 1986) mostly revealed dynamic non-linearities. PMID:3489703

  2. Bi-stability of amplitude modulation AFM in air: deterministic and stochastic outcomes for imaging biomolecular systems

    International Nuclear Information System (INIS)

    The dynamics of the oscillating microcantilever for amplitude modulation atomic force microscopy (AM AFM) operating in air is well understood theoretically but the experimental outcomes are still emerging. We use double-stranded DNA on mica as a model biomolecular system for investigating the connection between theory and experiment. A demonstration that the switching between the two cantilever oscillation states is stochastic in nature is achieved, and it can be induced by means of topographical anomalies on the surface. Whether one or the other attractor basin is accessed depends on the tip-sample separation history used to achieve the imaging conditions, and we show that the behaviour is reproducible when the tip is stable and well characterized. Emergence of background noise occurs in certain regions of parameter space regardless of whether two cantilever oscillation states coexist. The low state has been explored in detail and we note that at low to intermediate values of the free amplitude, noise-free imaging is achieved. The outcomes shown here are general and demonstrate that a thorough and systematic experimental approach in conjunction with standard modelling gives insight into the mechanisms behind image contrast formation in AM AFM in air.

  3. Amplitude modulation and relaxation-oscillation of counterpropagating rolls within a broken-symmetry laser-induced electroconvection strip

    Science.gov (United States)

    Spiegel, Daniel R.; Johnson, Elliot R.; Saucedo, Skyler R.

    2006-03-01

    We report a liquid-crystal pattern-formation experiment in which we break the lateral (translational) symmetry of a nematic medium with a laser-induced thermal gradient. The work is motivated by an improved measurement (reported here) of the temperature dependence of the electroconvection threshold voltage in planar-nematic 4-methoxybenzylidene-4-butylaniline. In contrast with other broken-symmetry-pattern studies that report a uniform drift, we observe a strip of counterpropagating rolls that collide at a sink point, and a strong temporally periodic amplitude modulation within a width of 3-4 rolls about the sink point. The time dependence of the amplitude at a fixed position is periodic but displays a nonsinusoidal relaxation-oscillation profile. After reporting experimental results based on spacetime contours and wave number profiles, along with a measurement of the change in the drift frequency with applied voltage at a fixed control parameter, we propose some potential guidelines for a theoretical model based on saddle-point solutions for Eckhaus-unstable states and coupled complex Ginzburg-Landau equations.

  4. Aged-related loss of temporal processing: altered responses to amplitude modulated tones in rat dorsal cochlear nucleus.

    Science.gov (United States)

    Schatteman, T A; Hughes, L F; Caspary, D M

    2008-06-12

    Loss of temporal processing is characteristic of age-related loss of speech understanding observed in the elderly. Inhibitory glycinergic circuits provide input onto dorsal cochlear nucleus (DCN) projection neurons which likely serve to modulate excitatory responses to time-varying complex acoustic signals. The present study sought to test the hypothesis that age-related loss of inhibition would compromise the ability of output neurons to encode sinusoidally amplitude modulated (SAM) tones. Extracellular recordings were obtained from young and aged FBN rat DCN putative fusiform cells. Stimuli were SAM tones at three modulation depths (100, 50, and 20%) at 30 dB hearing level with the carrier frequency set to the unit's characteristic frequency. Discharge rate and synchrony were calculated to describe SAM responses. There were significant age-related changes in the shape and peak vector strength [best modulation frequency (BMF)] of temporal modulation transfer functions (tMTFs), with no significant age-related changes in rate modulation transfer functions (rMTFs) at BMF. Young neurons exhibited band-pass tMTFs for most SAM conditions while aged fusiform cells exhibited significantly more low-pass or double-peaked tMTFs. There were significant differences in tMTFs between buildup, pauser-buildup, and wide-chopper temporal response types. Young and aged wide-choppers displayed significantly lower vector strength values than the other two temporal DCN response types. Age-related decreases in the number of pauser-buildup response types and increases in wide-chopper types reported previously, could account, in part, for the observed loss of temporal coding of the aged fusiform cell. Age-related changes in SAM coding were similar to changes observed with receptor blockade of glycinergic inhibition onto fusiform cells and consistent with previously observed age-related loss of endogenous glycine levels and changes in normal adult glycine receptor function. DCN changes in SAM coding could, in part, underpin temporal processing deficits observed in the elderly. PMID:18384967

  5. Multi-frequency amplitude modulated non-contact atomic force microscopy for nanoscale dielectric measurements

    Science.gov (United States)

    Kumar, Bharat; Bonvallet, Joseph; Crittenden, Scott

    2012-02-01

    Multi-frequency non-contact atomic force microscopy with amplitude feedback in air was used to obtain the dielectric constant of ultra-thin films on metallic substrates. The cantilever was excited at its second bending mode by applying an AC electric field between the substrate and cantilever. The capacitance gradient between the cantilever tip and sample substrate was obtained by measuring the capacitive force driving the cantilever at its second bending mode. An analytic expression relating capacitance and dielectric constant of thin film was then used to fit the experimental data and the dielectric constant was obtained from the fit parameters. The method was validated by obtaining the dielectric constants of self-assembled monolayers of thiol molecules (2.0 ±0.1) on gold substrate, and sputtered SiO2 (3.6 ±0.07) thin film. The high Q-factor of the second bending mode of the cantilever increases the accuracy of capacitive measurements while the low applied potentials minimize the likelihood of variation of dielectric constants at high field strength and of damage from dielectric breakdown of air.

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

    OpenAIRE

    Thanassoulas, C.; Klentos, V.; Verveniotis, G.

    2010-01-01

    Starting from the observation that quite often the Earth's oscillating electric field varies in amplitude, a mechanism is postulated that accounts for these observations. That mechanism is the piezoelectric one driven by the M1 and K1 tidal components. It is demonstrated how the system: piezoelectricity triggered in the lithosphere - M1 and K1 tidal components is activated and produces the amplitude modulated Earth's oscillating electric field. This procedure is linked to th...

  7. Potencial Evocado Auditivo de Estado Estável com estímulo de ruído branco modulado em amplitude em triagem auditiva neonatal Neonatal hearing screening using auditory steady state responses with amplitude modulated white noise stimuli

    Directory of Open Access Journals (Sweden)

    Danielle Gomes Pinto

    2012-06-01

    Full Text Available OBJETIVO: verificar a utilização do estímulo ruído branco, modulado em amplitude, no exame de Potencial Evocado Auditivo de Estado Estável (PEAEE. MÉTODO: foram avaliados 30 neonatos e lactentes, na Maternidade do Hospital das Clínicas da UFPE, que realizaram os exames de Emissões Otoacústicas Transientes (EOAT e PEAEE, com ruído branco de amplitude modulada. RESULTADOS: para o exame de PEAEE, sugere-se que a intensidade ideal para o ponto de corte seja 50 dB NPS, para os casos com passa na triagem auditiva, com o exame de EOAT. CONCLUSÃO: o exame de PEAEE, realizado com ruído branco, modulado em amplitude, parece ser promissor como ferramenta de triagem auditiva. Entretanto, estudos são necessários para observar a relação entre os limiares das respostas auditivas de estado estável utilizando-se tons puros e ruído branco, a fim de melhor elucidar e definir parâmetros e protocolos de sua utilização.PURPOSE: to check the use of amplitude modulated white noise as a stimulus for the auditory steady state response. METHOD: thirty neonates were evaluated with transient otoacoustic emissions and auditory steady state response, with amplitude modulate white noise, at the Clinical Hospital in the Federal University of Pernambuco. RESULTS: for the auditory steady state response, it is suggested that the cut point intensity related with normal hearing is 50 dB SPL, as it was related to the presence of transient otoacoustic emissions. CONCLUSION: the auditory steady state response, evoked with amplitude modulate white noise seems to be promissory as a tool for hearing screening. More studies need to be done in order to better establish the hearing threshold and to define more precise protocols for its employment.

  8. Potencial Evocado Auditivo de Estado Estável com estímulo de ruído branco modulado em amplitude em triagem auditiva neonatal / Neonatal hearing screening using auditory steady state responses with amplitude modulated white noise stimuli

    Scientific Electronic Library Online (English)

    Danielle Gomes, Pinto; Silvana Maria Sobral, Griz; Otávio Gomes, Lins.

    2012-06-01

    Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: verificar a utilização do estímulo ruído branco, modulado em amplitude, no exame de Potencial Evocado Auditivo de Estado Estável (PEAEE). MÉTODO: foram avaliados 30 neonatos e lactentes, na Maternidade do Hospital das Clínicas da UFPE, que realizaram os exames de Emissões Otoacústicas Tran [...] sientes (EOAT) e PEAEE, com ruído branco de amplitude modulada. RESULTADOS: para o exame de PEAEE, sugere-se que a intensidade ideal para o ponto de corte seja 50 dB NPS, para os casos com passa na triagem auditiva, com o exame de EOAT. CONCLUSÃO: o exame de PEAEE, realizado com ruído branco, modulado em amplitude, parece ser promissor como ferramenta de triagem auditiva. Entretanto, estudos são necessários para observar a relação entre os limiares das respostas auditivas de estado estável utilizando-se tons puros e ruído branco, a fim de melhor elucidar e definir parâmetros e protocolos de sua utilização. Abstract in english PURPOSE: to check the use of amplitude modulated white noise as a stimulus for the auditory steady state response. METHOD: thirty neonates were evaluated with transient otoacoustic emissions and auditory steady state response, with amplitude modulate white noise, at the Clinical Hospital in the Fede [...] ral University of Pernambuco. RESULTS: for the auditory steady state response, it is suggested that the cut point intensity related with normal hearing is 50 dB SPL, as it was related to the presence of transient otoacoustic emissions. CONCLUSION: the auditory steady state response, evoked with amplitude modulate white noise seems to be promissory as a tool for hearing screening. More studies need to be done in order to better establish the hearing threshold and to define more precise protocols for its employment.

  9. The influence of spread of excitation on the detection of amplitude modulation imposed on sinusoidal carriers at high levels.

    Science.gov (United States)

    Millman, Rebecca E; Bacon, Sid P

    2008-02-01

    The improvement in amplitude modulation (AM) detection thresholds with increasing level of a sinusoidal carrier has been attributed to listening on the high-frequency side of the excitation pattern, where the growth of excitation is more linear, or to an increase in the number of "channels" via spread of excitation. In the present study, AM detection thresholds were measured using a 1000-Hz sinusoidal carrier. Thresholds for modulation frequencies of 4-64 Hz improved by about 10-20 dB as the carrier level increased from 10 dB SL (14.5 dB SPL on average) to 80 dB SPL. To minimize the use of spread of excitation with an 80-dB carrier, tonal "restrictors" with frequencies of 501, 801, 1210, and 1510 Hz were used alone and in combination. High-frequency restrictors elevated AM detection thresholds, whereas low-frequency restrictors did not, indicating that excitation on the high side is more important for detecting AM. Results of modeling suggest that the improvement in AM detection thresholds at high levels is likely due to the use of a relatively linear growth of response on the high-frequency side of the excitation pattern. PMID:18247903

  10. Gas Phase Photoacoustic Spectroscopy in the long-wave IR using Quartz Tuning Forks and Amplitude Modulated Quantum Cascade Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Wojcik, Michael D.; Phillips, Mark C.; Cannon, Bret D.

    2006-12-31

    A paper to accompany a 20 minute talk about the progress of a DARPA funded project called LPAS. ABSTRACT: We demonstrate the performance of a novel long-wave infrared photoacoustic laser absorbance spectrometer for gas-phase species using an amplitude modulated (AM) quantum cascade (QC) laser and a quartz tuning fork microphone. Photoacoustic signal was generated by focusing the output of a Fabry-Perot QC laser operating at 8.41 micron between the legs of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The QC laser was modulated at the resonant frequency of the tuning fork (32.8 kHz). This sensor was calibrated using the infrared absorber Freon-134a by performing a simultanious absorption measurement using a 35 cm absorption cell. The NEAS of this instrument was determined to be 2 x 10^-8 W cm^-1 /Hz^1/2 and the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.

  11. Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769

    CERN Document Server

    Aerts, C; Catala, C; Neiner, C; Briquet, M; Castro, N; Schmid, V S; Scardia, M; Rainer, M; Poretti, E; Papics, I; Degroote, P; Bloemen, S; Oestensen, R H; Auvergne, M; Baglin, A; Baudin, F; Michel, E; Samadi, R

    2013-01-01

    {We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD\\,46769 ($V=5.79$). We also attempt to detect a magnetic field in the target.} {We analyse a 23-day oversampled CoRoT light curve after detrending, as well as spectroscopic follow-up data, by using standard Fourier analysis and Phase Dispersion Minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assumping a dipole field.} {In the CoRoT data, we detect a dominant period of 4.84\\,d with an amplitude of 87\\,ppm, and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69\\,d. Subtraction of the rotational modulation signal does not revea...

  12. Auditory distance coding in rabbit midbrain neurons and human perception: monaural amplitude modulation depth as a cue.

    Science.gov (United States)

    Kim, Duck O; Zahorik, Pavel; Carney, Laurel H; Bishop, Brian B; Kuwada, Shigeyuki

    2015-04-01

    Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments. Stimulus level was constant across distance. With increasing modulation depth, some rabbit inferior colliculus neurons increased firing rates whereas others decreased. These neurons exhibited monotonic relationships between firing rates and distance for monaurally presented noise when two conditions were met: (1) the sound had AM, and (2) the environment was reverberant. The firing rates as a function of distance remained approximately constant without AM in either environment and, in an anechoic condition, even with AM. We corroborated this finding by reproducing the distance sensitivity using a neural model. We also conducted a human psychophysical study using similar methods. Normal-hearing listeners reported perceived distance in response to monaural 1 octave 4 kHz noise source sounds presented at distances of 35-200 cm. We found parallels between the rabbit neural and human responses. In both, sound distance could be discriminated only if the monaural sound in reverberation had AM. These observations support the hypothesis. When other cues are available (e.g., in binaural hearing), how much the auditory system actually uses the AM as a distance cue remains to be determined. PMID:25834060

  13. Noisy galvanic vestibular stimulation modulates the amplitude of EEG synchrony patterns.

    Science.gov (United States)

    Kim, Diana J; Yogendrakumar, Vignan; Chiang, Joyce; Ty, Edna; Wang, Z Jane; McKeown, Martin J

    2013-01-01

    Noisy galvanic vestibular stimulation has been associated with numerous cognitive and behavioural effects, such as enhancement of visual memory in healthy individuals, improvement of visual deficits in stroke patients, as well as possibly improvement of motor function in Parkinson's disease; yet, the mechanism of action is unclear. Since Parkinson's and other neuropsychiatric diseases are characterized by maladaptive dynamics of brain rhythms, we investigated whether noisy galvanic vestibular stimulation was associated with measurable changes in EEG oscillatory rhythms within theta (4-7.5 Hz), low alpha (8-10 Hz), high alpha (10.5-12 Hz), beta (13-30 Hz) and gamma (31-50 Hz) bands. We recorded the EEG while simultaneously delivering noisy bilateral, bipolar stimulation at varying intensities of imperceptible currents - at 10, 26, 42, 58, 74 and 90% of sensory threshold - to ten neurologically healthy subjects. Using standard spectral analysis, we investigated the transient aftereffects of noisy stimulation on rhythms. Subsequently, using robust artifact rejection techniques and the Least Absolute Shrinkage Selection Operator regression and cross-validation, we assessed the combinations of channels and power spectral features within each EEG frequency band that were linearly related with stimulus intensity. We show that noisy galvanic vestibular stimulation predominantly leads to a mild suppression of gamma power in lateral regions immediately after stimulation, followed by delayed increase in beta and gamma power in frontal regions approximately 20-25 s after stimulation ceased. Ongoing changes in the power of each oscillatory band throughout frontal, central/parietal, occipital and bilateral electrodes predicted the intensity of galvanic vestibular stimulation in a stimulus-dependent manner, demonstrating linear effects of stimulation on brain rhythms. We propose that modulation of neural oscillations is a potential mechanism for the previously-described cognitive and motor effects of vestibular stimulation, and noisy galvanic vestibular stimulation may provide an additional non-invasive means for neuromodulation of functional brain networks. PMID:23874865

  14. Eight-state trellis-coded optical modulation with signal constellations of four-dimensional M-ary quadrature-amplitude modulation.

    Science.gov (United States)

    Ishimura, Shota; Kikuchi, Kazuro

    2015-03-01

    We apply the eight-state trellis-coded modulation (TCM) using signal constellations of four-dimensional M-ary quadrature-amplitude modulation (4D-MQAM) to optical communication systems for the first time to our knowledge. In the TCM scheme, the free distance of the trellis diagram is equal to the minimum distance between constellation points in partitioned subsets, which enlarges the coding gain effectively. In fact, its asymptotic power efficiency is 3-dB larger than that of the set-partitioned 4D-MQAM (SP-4D-MQAM) format, while their spectral efficiencies are the same. Such theoretical predictions are confirmed through computer simulations on eight-state TCM with constellations of 4D-4QAM (i.e., 4D quadrature phase-shift keying: 4D-QPSK) and 4D-16QAM. In particular, eight-state TCM with 4D-QPSK constellations is practically important because of its simple encoder structure, relatively low computational cost, and high coding gain against dual-polarization QPSK (DP-QPSK) and SP-4D-QPSK. Through measurements of its bit-error rate (BER) performance, we confirm that the coding gain against DP-QPSK is about 3 dB at BER=10-3. PMID:25836886

  15. Pressure and cold pain threshold in healthy subjects undergoing interferential current at different amplitude modulated frequencies / Avaliação do limiar de dor à pressão e ao frio em indivíduos saudáveis submetidos à corrente interferencial em diferentes frequências de amplitude modulada

    Scientific Electronic Library Online (English)

    Alexandra de Oliveira, Claro; Bruna Akie, Kanezawa; Michele de, Camargo; Vanessa Maria, Paes; José Luiz Marinho, Portolez; Gladson Ricardo Flor, Bertolini.

    2014-09-01

    Full Text Available JUSTIFICATIVA E OBJETIVOS: A corrente interferencial é um método de eletroestimulação bastante utilizado com finalidades analgésicas, porém, existem controvérsias com relação aos seus parâmetros de uso. O objetivo do estudo foi comparar diferentes frequências de amplitude modulada, da corrente inte [...] rferencial, sobre o limiar de dor à pressão e ao frio, em voluntários saudáveis. MÉTODOS: Trata-se de um ensaio cruzado, aleatório e com avaliadores e avaliados encobertos, de caráter quantitativo. Participaram deste estudo 20 voluntários subdivididos em quatro grupos, que durante quatro semanas passaram por diferentes frequências de amplitude modulada. Foram avaliados os limiares da dor à pressão e ao frio em quatro momentos distintos - no início, logo após eletroestimulação, 20 e 60 minutos após. Como forma de eletroestimulação foi utilizada a corrente interferencial nas frequências de amplitude modulada de 1Hz, 10Hz e 100Hz, com frequência de base de 4.000Hz, sendo que em uma determinada semana os voluntários recebiam placebo (0Hz). RESULTADOS: Não houve diferença significativa nas comparações dentro das frequências, nem entre elas e o grupo placebo. CONCLUSÃO: O uso da corrente interferencial nas frequências de amplitude modulada de 1Hz, 10Hz e 100Hz não produziu alterações nos limiares de dor ao frio e à pressão, semelhante ao encontrado para o grupo placebo. Abstract in english BACKGROUND AND OBJECTIVES: The interferential current is an electrical stimulation method widely used with analgesic purposes; however, there are controversies regarding their usage parameters. The aim of this study was to compare different amplitude modulated frequencies of the interferential curr [...] ent on the pressure and cold pain threshold in healthy volunteers. METHODS: This is a crossover, randomized and blinded evaluators and evaluated in quantitative character test. Participants were 20 volunteers divided into four groups, who for four weeks were subject to different modulated frequencies. Thresholds of pressure and cold pain in four different times were evaluated - at the beginning, right after electric stimulation, 20 and 60 minutes after. As a form of electrical stimulation, interferential current was used at modulated amplitude frequencies of 1Hz, 10Hz and 100Hz with base frequency of 4,000Hz, being that in a particular week volunteers received placebo (0Hz). RESULTS: There has been no significant difference in comparisons within frequencies or between them and the placebo group. CONCLUSION: The use of amplitude modulated frequencies of interferential current of 1Hz, 10Hz and 100Hz did not change cold and pressure pain thresholds, similar to what has been found for the placebo group

  16. Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds II: single-neuron recordings.

    Science.gov (United States)

    Dietz, Mathias; Marquardt, Torsten; Stange, Annette; Pecka, Michael; Grothe, Benedikt; McAlpine, David

    2014-05-01

    Recently, with the use of an amplitude-modulated binaural beat (AMBB), in which sound amplitude and interaural-phase difference (IPD) were modulated with a fixed mutual relationship (Dietz et al. 2013b), we demonstrated that the human auditory system uses interaural timing differences in the temporal fine structure of modulated sounds only during the rising portion of each modulation cycle. However, the degree to which peripheral or central mechanisms contribute to the observed strong dominance of the rising slope remains to be determined. Here, by recording responses of single neurons in the medial superior olive (MSO) of anesthetized gerbils and in the inferior colliculus (IC) of anesthetized guinea pigs to AMBBs, we report a correlation between the position within the amplitude-modulation (AM) cycle generating the maximum response rate and the position at which the instantaneous IPD dominates the total neural response. The IPD during the rising segment dominates the total response in 78% of MSO neurons and 69% of IC neurons, with responses of the remaining neurons predominantly coding the IPD around the modulation maximum. The observed diversity of dominance regions within the AM cycle, especially in the IC, and its comparison with the human behavioral data suggest that only the subpopulation of neurons with rising slope dominance codes the sound-source location in complex listening conditions. A comparison of two models to account for the data suggests that emphasis on IPDs during the rising slope of the AM cycle depends on adaptation processes occurring before binaural interaction. PMID:24554782

  17. FPGA Implementation of an Amplitude-Modulated Continuous-Wave Ultrasonic Ranger Using Restructured Phase-Locking Scheme

    Directory of Open Access Journals (Sweden)

    P. A. Janakiraman

    2010-01-01

    Full Text Available An accurate ultrasonic range finder employing Sliding Discrete Fourier Transform (SDFT based restructured phase-locked loop (RPLL, which is an improved version of the recently proposed integrated phase-locking scheme (IPLL, has been expounded. This range finder principally utilizes amplitude-modulated ultrasonic waves assisted by an infrared (IR pilot signal. The phase shift between the envelope of the reference IR pilot signal and that of the received ultrasonic signal is proportional to the range. The extracted envelopes are filtered by SDFT without introducing any additional phase shift. A new RPLL is described in which the phase error is driven to zero using the quadrature signal derived from the SDFT. Further, the quadrature signal is reinforced by another cosine signal derived from a lookup table (LUT. The pulse frequency of the numerically controlled oscillator (NCO is extremely accurate, enabling fine tuning of the SDFT and RPLL also improves the lock time for the 50?Hz input signal to 0.04?s. The percentage phase error for the range 0.6?m to 6?m is about 0.2%. The VHDL codes generated for the various signal processing steps were downloaded into a Cyclone FPGA chip around which the ultrasonic ranger had been built.

  18. Characterization of a single molecular QCA cell by Q-control enhanced amplitude modulation atomic force microscopy

    International Nuclear Information System (INIS)

    Major technical challenges for reduction of device sizes for computation and memory are the interconnection and power dissipation problems. Molecular quantum-dot cellular automata (QCA) have been proposed as solutions to this problem. Silicon phthalocyanine (SiPc) is a possible candidate for a molecular QCA element. Therefore, it is important to develop an in situ observation technique to visualize individual SiPc molecules. We report here the first image of a single SiPc dimer in air by using quality factor control (Q-control) enhanced amplitude modulation atomic force microscopy (AFM) and an investigation of the interaction forces between the tip and SiPc dimer. The AFM was operated at 0% relative humidity in an ultrapure nitrogen environment either with or without Q-control. Theoretical simulations using the point-mass description of the AFM, demonstrated that Q-enhancement reduced the force exerted from the tip to the sample surface. Our results, consistent with theory, demonstrated that the image force was reduced and a greater height and a larger size were measured. The advantages of this method can be extended to the AFM observation of other 'soft' structures, and these results can be useful for a wider community

  19. Characterization of a single molecular QCA cell by Q-control enhanced amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, I. [Department of Electrical and Computer Engineering, University of Tennessee, TN 37996-2100 (United States)]. E-mail: leei@ornl.gov; Sarveswaran, V. [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Lieberman, M. [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Greenbaum, E. [Oak Ridge National Laboratory, Chemical Science Division, Oak Ridge, TN 37831-6194 (United States)

    2006-06-15

    Major technical challenges for reduction of device sizes for computation and memory are the interconnection and power dissipation problems. Molecular quantum-dot cellular automata (QCA) have been proposed as solutions to this problem. Silicon phthalocyanine (SiPc) is a possible candidate for a molecular QCA element. Therefore, it is important to develop an in situ observation technique to visualize individual SiPc molecules. We report here the first image of a single SiPc dimer in air by using quality factor control (Q-control) enhanced amplitude modulation atomic force microscopy (AFM) and an investigation of the interaction forces between the tip and SiPc dimer. The AFM was operated at 0% relative humidity in an ultrapure nitrogen environment either with or without Q-control. Theoretical simulations using the point-mass description of the AFM, demonstrated that Q-enhancement reduced the force exerted from the tip to the sample surface. Our results, consistent with theory, demonstrated that the image force was reduced and a greater height and a larger size were measured. The advantages of this method can be extended to the AFM observation of other 'soft' structures, and these results can be useful for a wider community.

  20. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy.

    Science.gov (United States)

    Marutschke, Christoph; Walters, Deron; Walters, Deron; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-22

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic - yet decisive - question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface. PMID:25074402

  1. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

    Science.gov (United States)

    Nguyen, Thu-Mai; Arnal, Bastien; Song, Shaozhen; Huang, Zhihong; Wang, Ruikang K.; O'Donnell, Matthew

    2015-01-01

    Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6).

  2. On the relevance of the atomic-scale contact potential difference by amplitude-modulation and frequency-modulation Kelvin probe force microscopy

    International Nuclear Information System (INIS)

    The influence of short-range electrostatic forces on the measured local contact potential difference (CPD) by means of amplitude-modulation and frequency-modulation Kelvin probe force microscopy (AM- and FM-KPFM) is discussed on the base of numerical and analytical descriptions of both methods. The goal of this work is to help in interpreting recent experimental results reporting atomically resolved CPD images, in particular on bulk insulating samples. The discussion is carried out on the basis of spectroscopic curves. The expression of the bias-dependent electrostatic force is derived from a previous work and is estimated between a tip with simple geometry and the (001) facet of a perfect alkali halide single crystal. The force, with a short-range character, scales as a second-order polynomial function of the bias voltage. It is stated that the linear term is responsible for the occurrence of the atomic-scale CPD contrast, while the quadratic one, involving the sample polarization, accounts for the detected signal by the KPFM methods. Nevertheless, analytical and numerical approaches stress the influence of the linear term on the measured CPD which intrinsically hinders the possibility to perform quantitative CPD measurements, but also makes the measured 'pseudo-CPD' strongly deviating from the surface potential. Hence, in the short-range regime, AM- or FM-KPFM measurements neither reflect the CPD nor the local surface potential, but rather an effective value which iial, but rather an effective value which is convoluted by the geometric parameters of the tip, the so-called local CPD. It is also stated that the local CPD measured by means of AM- or FM-KPFM differs when sub-nanometer vibration amplitudes of the cantilever are used. Otherwise, AM- and FM-KPFM measurements should be almost similar. At last, the influence of long-range, capacitive, electrostatic forces is discussed in conjunction with the short-range ones. This allows us to draw conclusions regarding the distance dependence of the local CPD which then exhibits a resonant behavior as a function of the tip-surface separation. This phenomenon is expected to play a role in the KPFM imaging process.

  3. On the relevance of the atomic-scale contact potential difference by amplitude-modulation and frequency-modulation Kelvin probe force microscopy.

    Science.gov (United States)

    Nony, Laurent; Bocquet, Franck; Loppacher, Christian; Glatzel, Thilo

    2009-07-01

    The influence of short-range electrostatic forces on the measured local contact potential difference (CPD) by means of amplitude-modulation and frequency-modulation Kelvin probe force microscopy (AM- and FM-KPFM) is discussed on the base of numerical and analytical descriptions of both methods. The goal of this work is to help in interpreting recent experimental results reporting atomically resolved CPD images, in particular on bulk insulating samples. The discussion is carried out on the basis of spectroscopic curves. The expression of the bias-dependent electrostatic force is derived from a previous work and is estimated between a tip with simple geometry and the (001) facet of a perfect alkali halide single crystal. The force, with a short-range character, scales as a second-order polynomial function of the bias voltage. It is stated that the linear term is responsible for the occurrence of the atomic-scale CPD contrast, while the quadratic one, involving the sample polarization, accounts for the detected signal by the KPFM methods. Nevertheless, analytical and numerical approaches stress the influence of the linear term on the measured CPD which intrinsically hinders the possibility to perform quantitative CPD measurements, but also makes the measured 'pseudo-CPD' strongly deviating from the surface potential. Hence, in the short-range regime, AM- or FM-KPFM measurements neither reflect the CPD nor the local surface potential, but rather an effective value which is convoluted by the geometric parameters of the tip, the so-called local CPD. It is also stated that the local CPD measured by means of AM- or FM-KPFM differs when sub-nanometer vibration amplitudes of the cantilever are used. Otherwise, AM- and FM-KPFM measurements should be almost similar. At last, the influence of long-range, capacitive, electrostatic forces is discussed in conjunction with the short-range ones. This allows us to draw conclusions regarding the distance dependence of the local CPD which then exhibits a resonant behavior as a function of the tip-surface separation. This phenomenon is expected to play a role in the KPFM imaging process. PMID:19509441

  4. Stochastic amplitude-modulated stretching of rabbit flexor digitorum profundus tendons reduces stiffness compared to cyclic loading but does not affect tenocyte metabolism

    Directory of Open Access Journals (Sweden)

    Steiner Thomas H

    2012-11-01

    Full Text Available Abstract Background It has been demonstrated that frequency modulation of loading influences cellular response and metabolism in 3D tissues such as cartilage, bone and intervertebral disc. However, the mechano-sensitivity of cells in linear tissues such as tendons or ligaments might be more sensitive to changes in strain amplitude than frequency. Here, we hypothesized that tenocytes in situ are mechano-responsive to random amplitude modulation of strain. Methods We compared stochastic amplitude-modulated versus sinusoidal cyclic stretching. Rabbit tendon were kept in tissue-culture medium for twelve days and were loaded for 1h/day for six of the total twelve culture days. The tendons were randomly subjected to one of three different loading regimes: i stochastic (2 – 7% random strain amplitudes, ii cyclic_RMS (2–4.42% strain and iii cyclic_high (2 - 7% strain, all at 1 Hz and for 3,600 cycles, and one unloaded control. Results At the end of the culture period, the stiffness of the “stochastic” group was significantly lower than that of the cyclic_RMS and cyclic_high groups (both, p Conclusions We conclude that, despite an equivalent metabolic response, stochastically stretched tendons suffer most likely from increased mechanical microdamage, relative to cyclically loaded ones, which is relevant for tendon regeneration therapies in clinical practice.

  5. Reconstructing 3-D maps of the local viscoelastic properties using a finite-amplitude modulated radiation force.

    Science.gov (United States)

    Giannoula, Alexia; Cobbold, Richard; Bezerianos, Anastasios

    2014-02-01

    A modulated acoustic radiation force, produced by two confocal tone-burst ultrasound beams of slightly different frequencies (i.e. 2.0 MHz ± ?f/2, where ?f is the difference frequency), can be used to remotely generate modulated low-frequency (?f ? 500 Hz) shear waves in attenuating media. By appropriately selecting the duration of the two beams, the energy of the generated shear waves can be concentrated around the difference frequency (i.e., ?f ± ?f/2). In this manner, neither their amplitude nor their phase information is distorted by frequency-dependent effects, thereby, enabling a more accurate reconstruction of the viscoelastic properties. Assuming a Voigt viscoelastic model, this paper describes the use of a finite-element-method model to simulate three-dimensional (3-D) shear-wave propagation in viscoelastic media containing a spherical inclusion. Nonlinear propagation is assumed for the two ultrasound beams, so that higher harmonics are developed in the force and shear spectrum. Finally, an inverse reconstruction algorithm is used to extract 3-D maps of the local shear modulus and viscosity from the simulated shear-displacement fields based on the fundamental and second-harmonic component. The quality of the reconstructed maps is evaluated using the contrast between the inclusion and the background and the contrast-to-noise ratio (CNR). It is shown that the shear modulus can be accurately reconstructed based on the fundamental component, such that the observed contrast deviates from the true contrast by a root-mean-square-error (RMSE) of only 0.38 and the CNR is greater than 30 dB. If the second-harmonic component is used, the RMSE becomes 1.54 and the corresponding CNR decreases by approximately 10-15 dB. The reconstructed shear viscosity maps based on the second harmonic are shown to be of higher quality than those based on the fundamental. The effects of noise are also investigated and a fusion operation between the two spectral components is applied to enhance the reconstruction quality. Finally, a modified shear-wave spectroscopy technique, shown to be more robust to noise, is described for the estimation of the viscoelastic properties inside and outside the spherical inclusion under conditions of increased noise. PMID:24011778

  6. Phase-locked response characteristics of single neurons in the frog "cochlear nucleus" to steady-state and sinusoidal-amplitude-modulated tones.

    Science.gov (United States)

    Feng, A S; Lin, W Y

    1994-11-01

    1. We made extracellular recordings from 164 single neurons in the frog dorsal medullary nucleus (DMN), a homologue of the cochlear nucleus. Phase-locked responses to tones at the unit's characteristic frequency (CF) and to off-CF tones were evaluated. We also stimulated units with tones at CF that were amplitude modulated sinusoidally between 5 and 1,000 Hz and examined responses to these stimuli. 2. Results showed that single neurons in the frog DMN displayed phase-locked discharges to tones at frequencies PL-3) steady-state firing rates to CF stimulation. The phasic neurons showed poor phase-locking capacities at all tone frequencies. 4. The frequency range of phase-locking to amplitude-modulated stimuli was also different for the different cell types, as evidenced by the units' modulation transfer functions (MTFs). The primarylike neurons exhibited mostly all-pass or low-pass sync-based MTFs. The mean upper cutoff frequencies for primarylike neurons having low-pass MTFs were 155 Hz for PL-1 neurons, 176 Hz for PL-2 neurons, and 218 Hz for PL-3 neurons. Pauser, chopper, phasic, and phasic-burst neurons gave mostly low-pass MTFs having a mean upper cutoff frequency of 219, 235, 242, and 251 Hz, respectively. 5. The phase-locking ability of DMN neurons to tones and to amplitude-modulated stimuli are compared with those of frog's primary afferent fibers and with those of avian and mammalian cochlear nucleus neurons. The significance of results in terms of sound localization and sound pattern recognition is discussed. PMID:7884454

  7. Encoding of the amplitude modulation of pulsatile electrical stimulation in the feline cochlear nucleus by neurons in the inferior colliculus; effects of stimulus pulse rate

    Science.gov (United States)

    McCreery, Douglas; Han, Martin; Pikov, Victor; Yadav, Kamal; Pannu, Satinderpall

    2013-10-01

    Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This ‘constant maximum’ protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of ABIs may benefit from using pulse rates greater than those presently used in most ABIs, and by sound processing strategies that enhance the modulation depth of the electrical stimulus while preserving dynamic range.

  8. Residues in Na(+) channel D3-S6 segment modulate both batrachotoxin and local anesthetic affinities.

    OpenAIRE

    Wang, S. Y.; Nau, C.; Wang, G. K.

    2000-01-01

    Batrachotoxin (BTX) alters the gating of voltage-gated Na(+) channels and causes these channels to open persistently, whereas local anesthetics (LAs) block Na(+) conductance. The BTX and LA receptors have been mapped to several common residues in D1-S6 and D4-S6 segments of the Na(+) channel alpha-subunit. We substituted individual residues with lysine in homologous segment D3-S6 of the rat muscle mu1 Na(+) channel from F1274 to N1281 to determine whether additional residues are involved in B...

  9. Amplitude-modulation detection by recreational-noise-exposed humans with near-normal hearing thresholds and its medium-term progression

    OpenAIRE

    Stone, Michael A.; Moore, Brian C. J.

    2014-01-01

    Noise exposure can affect the functioning of cochlear inner and outer hair cells (IHC/OHC), leading to multiple perceptual changes. This work explored possible changes in detection of amplitude modulation (AM) at three Sensation Levels (SL) for carrier frequencies of 3, 4 and 6 kHz. There were two groups of participants, aged 19 to 24 (Young) and 26 to 35 (Older) years. All had near-normal audiometric thresholds. Participants self-assessed exposure to high-level noise in recreational setting...

  10. Amplitude Modulation Approach for Real-Time Algorithms of ECG-Derived Respiration / Desarrollo de Algoritmos en Tiempo Real para Derivar la Respiración del ECG Bajo el Criterio de Amplitud Modulada

    Scientific Electronic Library Online (English)

    J.L., Vargas-Luna; W., Mayr; J.A., Cortés-Ramírez.

    Full Text Available Este trabajo presenta una metodología para la extracción de la actividad respiratoria derivada de un ECG (EDR, por sus siglas en ingles), basado en el enfoque de amplitud modulada (AM). Esto permite redefinir las metodologías actuales para obtener una señal EDR más continua, con altos factores de co [...] rrelación y un retraso menor entre la EDR y la actividad respiratoria. Se implementaron dos algoritmos: uno utilizando la modulación de la amplitud del pico R (EDRAM) y el otro aplicando un filtro paso-banda en el espectro de frecuencia de la respiración. A diferencia de otros trabajos en la literatura, se utilizan filtros convencionales de bajo orden pero sin sacrificar el factor de correlación (0.76 y 0.67) y manteniendo un retardo de ?0.27s (con EDRAM) en un ciclo de ?6s. Se realizó una prueba de robustez, donde se muestra una tolerancia a ruido blanco de hasta un 20% del valor máximo antes de que el factor de correlación bajara considerablemente. El algoritmo EDRAM se aplicó con éxito en un prototipo de sistema portable. Las dos metodologías propuestas muestran ventajas como el procesamiento en tiempo real y robustez bajo ciertos ruidos. La perspectiva de AM propuesta soporta el uso de ambos algoritmos para aplicaciones típicas con alta eficiencia, bajo costo computacional y facilidad de implementación. Estas características hacen que esta técnica facilite el desarrollo de sistemas portátiles, así como para incrementar la información de las bases de datos actuales. Abstract in english This work presents the development of an ECG-Derived Respiration (EDR) methodology based on the amplitude modulation approach. It allows to redefine actual methodologies in order to obtain a continuous EDR signals with high correlations and small delay between EDR and respiration activity. Two algor [...] ithms are implemented: one of them using the amplitude modulation of the R-peak (EDRAM) and another one applying a band-pass filter in the bandwidth of respiration. Unlike other techniques in literature, conventional low order filters are applied without sacrifice of correlation factor (0.76 and 0.67) and a minimum delay of 0.27s (with EDRAM) in a ?6s cycle. A robustness test was performed, and it shows a noise tolerance of up to 20% of the maximum value before its correlation factor drops considerably. The application into a wearable sensor was successfully implemented. The two methodologies proposed show advantages like real-time processing and robustness under certain noises. The proposed AM perspective supports the use of both algorithms for typical applications with high efficiency, low computational cost and ease of implementation. These characteristics result on a technique that facilitates the development of wearable systems, and to increase the information of actual databases.

  11. An atypical residue in the pore of Varroa destructor GABA-activated RDL receptors affects picrotoxin block and thymol modulation.

    Science.gov (United States)

    Price, Kerry L; Lummis, Sarah C R

    2014-10-18

    GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using two electrode voltage clamp electrophysiology we show that one substitution (T6'M) ablates picrotoxin inhibition and increases the potency of GABA. This mutation also alters the effect of thymol, which enhances both insect and mammalian GABA responses, and is widely used as a miticide. Thymol decreases the GABA EC50 of WT receptors, enhancing responses, but in T6'M-containing receptors it is inhibitory. The other 3 atypical residues have no major effects on either the GABA EC50, the picrotoxin potency or the effect of thymol. In conclusion we show that the RDL 6' residue is important for channel block, activation and modulation, and understanding its function also has the potential to prove useful in the design of Varroa-specific insecticidal agents. PMID:25460510

  12. Residual stress in a laser welded EUROFER blanket module assembly using non-destructive neutron diffraction techniques

    International Nuclear Information System (INIS)

    Highlights: • Residual stresses were determined in a welded EUROFER blanket assembly with integrated cooling channels. • Good agreement was seen between experimentally determined and predicted stresses. • We show that microstructure changes that occur in EUROFER steels during welding must be considered for residual stress determination. • An experimental route is proposed for validation of predicted stresses in reactor components using non-destructive diffraction techniques. - Abstract: Whilst the structural integrity and lifetime considerations in welded joints for blanket modules can be predicted using finite element software, it is essential to prove the validity of these simulations. This paper provides detailed analysis for the first time, of the residual stress state in a laser-welded sample with integral cooling channels. State-of-the-art non-destructive neutron diffraction was employed to determine the triaxial stress state and to understand microstructural changes around the heat affected zone. Synchrotron X-ray diffraction was used to probe the variation of strain-free lattice reference parameter around the weld zone allowing correction of the neutron measurements. This paper details an important experimental route to validation of predicted stresses in complex safety-critical reactor components for future applications

  13. Residual stress in a laser welded EUROFER blanket module assembly using non-destructive neutron diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, D.J., E-mail: d.hughes@warwick.ac.uk [WMG, University of Warwick, Coventry CV4 7AL (United Kingdom); Koukovini-Platia, E. [CERN, CH-1211 Geneva 23 (Switzerland); Heeley, E.L. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

    2014-02-15

    Highlights: • Residual stresses were determined in a welded EUROFER blanket assembly with integrated cooling channels. • Good agreement was seen between experimentally determined and predicted stresses. • We show that microstructure changes that occur in EUROFER steels during welding must be considered for residual stress determination. • An experimental route is proposed for validation of predicted stresses in reactor components using non-destructive diffraction techniques. - Abstract: Whilst the structural integrity and lifetime considerations in welded joints for blanket modules can be predicted using finite element software, it is essential to prove the validity of these simulations. This paper provides detailed analysis for the first time, of the residual stress state in a laser-welded sample with integral cooling channels. State-of-the-art non-destructive neutron diffraction was employed to determine the triaxial stress state and to understand microstructural changes around the heat affected zone. Synchrotron X-ray diffraction was used to probe the variation of strain-free lattice reference parameter around the weld zone allowing correction of the neutron measurements. This paper details an important experimental route to validation of predicted stresses in complex safety-critical reactor components for future applications.

  14. The evolution of strongly modulated, low-frequency, moderate-amplitude wave packets in a dispersive plasma

    International Nuclear Information System (INIS)

    The evolution of strongly modulated wave packets in a dispersive plasma that propagate parallel to the magnetic field is studied. Modulation effects are shown to reduce significantly (?30%) the rate of spreading from that due to dispersion alone. For fluidlike behavior, nonlinearity has its greatest impact on evolution when the linear sound speed and initial wave packet speeds are well matched, resulting in a strong coupling between the wave magnetic and sonic components. Ion kinetic processes reduce the impact of nonlinearity and cause the rate of spreading to approach that expected from dispersion alone as the ratio of ion and electron temperatures, Ti/Te?4. For ? approx-gt 1 and Ti/Te?1, the coupled waveforms correspond qualitatively to kinetic treatments of the derivative nonlinear Schroedinger (DNLS) equation

  15. Matter-wave solitons and finite-amplitude Bloch waves in optical lattices with a spatially modulated nonlinearity

    OpenAIRE

    Zhang, Jie-fang; Li, Yi-shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.

    2010-01-01

    We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices. By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite number of exact soliton solutions in terms of the Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite bandgap of the optical-lattice-induced spectrum. Starting from the exact solutions, we employ ...

  16. Tuning in on Cepheids: Radial velocity amplitude modulations. A source of systematic uncertainty for Baade-Wesselink distances

    OpenAIRE

    Anderson, Richard I.

    2014-01-01

    [Abridged] I report the discovery of modulations in radial velocity (RV) curves of four Galactic classical Cepheids and investigate their impact as a systematic uncertainty for Baade-Wesselink distances. Highly precise Doppler measurements were obtained using the Coralie high-resolution spectrograph since 2011. Particular care was taken to sample all phase points in order to very accurately trace the RV curve during multiple epochs and to search for differences in linear rad...

  17. Recording weak absorption spectra by the phase-shift method with deep amplitude and frequency modulation using a diode laser and a high Q cavity

    International Nuclear Information System (INIS)

    A method is suggested and developed for recording absorption spectra of particles in a high Q cavity from the phase delay of amplitude-modulated radiation generated by a tunable diode laser. The method features high spectral resolution and sensitivity. It is based on the experimentally established possibility of recording spectra in conditions of high-percentage modulation, under which the concomitant frequency deviation exceeds the bandwidth. This is achieved by processing in a special way the signals in the absorption recording channel of the spectrometer and concurrently measuring the radiation frequency variation parameters in real time. The method is experimentally implemented for the case of square-pulse modulation of the laser injection current. The absorption spectrum of water molecules is recorded in the region of 644 nm with a spectral resolution of 4.5 × 10?3 cm?1 and a sensitivity of ?7 × 10?11 cm?1 in terms of the absorption coefficient. Comparative measurements are taken by another well-known high-sensitivity laser technique ICOS. The broadening coefficients for some weak absorption water lines by helium are determined. Possible ways are discussed of further development of the method suggested. (paper)

  18. Two variable active site residues modulate response regulator phosphoryl group stability

    OpenAIRE

    Thomas, Stephanie A.; Brewster, Jocelyn A.; Bourret, Robert B.

    2008-01-01

    Many signal transduction networks control their output by switching regulatory elements on or off. To synchronize biological response with environmental stimulus, switching kinetics must be faster than changes in input. Two-component regulatory systems (used for signal transduction by bacteria, archaea, and eukaryotes) switch via phosphorylation or dephosphorylation of the receiver domain in response regulator proteins. Although receiver domains share conserved active site residues and simila...

  19. Modulation of Human Immunodeficiency Virus Type 1 Protease Autoprocessing by Charge Properties of Surface Residue 69?

    OpenAIRE

    Huang, Liangqun; Sayer, Jane M.; Swinford, Marie; Louis, John M.; Chen, Chaoping

    2009-01-01

    Mature, fully active human immunodeficiency virus protease (PR) is liberated from the Gag-Pol precursor via regulated autoprocessing. A chimeric protease precursor, glutathione S-transferase-transframe region (TFR)-PR-FLAG, also undergoes N-terminal autocatalytic maturation when it is expressed in Escherichia coli. Mutation of the surface residue H69 to glutamic acid, but not to several neutral or basic amino acids, impedes protease autoprocessing in bacteria and mammalian cells. Only a fract...

  20. The emerging characterization of lysine residue deacetylation on the modulation of mitochondrial function and cardiovascular biology

    OpenAIRE

    Lu, Zhongping; Scott, Iain; Webster, Bradley R.; Sack, Michael N.

    2009-01-01

    There is emerging recognition of a novel fuel and redox sensing regulatory program that controls cellular adaptation via non-histone protein lysine-residue acetyl post-translation modifications. This program functions in tissues with high energy demand and oxidative capacity and is highly enriched in the heart. Deacetylation is regulated by NAD+-dependent activation of the sirtuin family of proteins while acetyltransferase modifications are controlled by less clearly delineated acetyltransfer...

  1. Computational identification of residues that modulate voltage sensitivity of voltage-gated potassium channels

    Directory of Open Access Journals (Sweden)

    Li Bin

    2005-08-01

    Full Text Available Abstract Background Studies of the structure-function relationship in proteins for which no 3D structure is available are often based on inspection of multiple sequence alignments. Many functionally important residues of proteins can be identified because they are conserved during evolution. However, residues that vary can also be critically important if their variation is responsible for diversity of protein function and improved phenotypes. If too few sequences are studied, the support for hypotheses on the role of a given residue will be weak, but analysis of large multiple alignments is too complex for simple inspection. When a large body of sequence and functional data are available for a protein family, mature data mining tools, such as machine learning, can be applied to extract information more easily, sensitively and reliably. We have undertaken such an analysis of voltage-gated potassium channels, a transmembrane protein family whose members play indispensable roles in electrically excitable cells. Results We applied different learning algorithms, combined in various implementations, to obtain a model that predicts the half activation voltage of a voltage-gated potassium channel based on its amino acid sequence. The best result was obtained with a k-nearest neighbor classifier combined with a wrapper algorithm for feature selection, producing a mean absolute error of prediction of 7.0 mV. The predictor was validated by permutation test and evaluation of independent experimental data. Feature selection identified a number of residues that are predicted to be involved in the voltage sensitive conformation changes; these residues are good target candidates for mutagenesis analysis. Conclusion Machine learning analysis can identify new testable hypotheses about the structure/function relationship in the voltage-gated potassium channel family. This approach should be applicable to any protein family if the number of training examples and the sequence diversity of the training set that are necessary for robust prediction are empirically validated. The predictor and datasets can be found at the VKCDB web site 1.

  2. Modulation of copper site properties by remote residues determines the stability of plastocyanins

    OpenAIRE

    Mun?oz-lo?pez, F. J.; Frutos-beltra?n, Estrella; Di?az-moreno, Sofi?a; Di?az-moreno, Irene; Subi?as, G.; Rosa, Miguel A. La; Di?az-quintana, Antonio

    2010-01-01

    The metal cofactor determines the thermal stability in cupredoxins, but how the redox state of copper modulates their melting points remains unknown. The metal coordination environment is highly conserved in cyanobacterial plastocyanins. However, the oxidised form is more stable than the reduced one in thermophilic Phormidium, but the opposite occurs in mesophilic Synechocystis. We have performed neutral amino-acid substitutions at loops of Phormidium plastocyanin far from the copper site. No...

  3. Matter-wave solitons and finite-amplitude Bloch waves in optical lattices with spatially modulated nonlinearity

    International Nuclear Information System (INIS)

    We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.

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

    Science.gov (United States)

    Sinha, A. K.; Pathan, B. M.; Rajaram, R.; Rao, D. R. K.

    2002-01-01

    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 inconsistent with our observations.

  5. 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 inconsistent with our observations.

    Key words. Magnetospheric physics (magnetosphere – ionosphere interactions Ionosphere (ionosphere – magnetoshere interactions; ionospheric irregularities

  6. Modulation of copper site properties by remote residues determines the stability of plastocyanins.

    Science.gov (United States)

    Muñoz-López, Francisco J; Beltrán, Estrella Frutos; Díaz-Moreno, Sofía; Díaz-Moreno, Irene; Subías, Gloria; De la Rosa, Miguel A; Díaz-Quintana, Antonio

    2010-06-01

    The metal cofactor determines the thermal stability in cupredoxins, but how the redox state of copper modulates their melting points remains unknown. The metal coordination environment is highly conserved in cyanobacterial plastocyanins. However, the oxidised form is more stable than the reduced one in thermophilic Phormidium, but the opposite occurs in mesophilic Synechocystis. We have performed neutral amino-acid substitutions at loops of Phormidium plastocyanin far from the copper site. Notably, mutation P49G/G50P confers a redox-dependent thermal stability similar to that of the mesophilic plastocyanin. Moreover, X-ray absorption spectroscopy reveals that P49G/G50P mutation makes the electron density distribution at the oxidised copper site shift towards that of Synechocystis plastocyanin. PMID:20398655

  7. Reactive control processes contributing to residual switch cost and mixing cost across the adult lifespan

    OpenAIRE

    Whitson, Lisa R.; Karayanidis, Frini; Fulham, Ross; Provost, Alexander; Michie, Patricia T.; Heathcote, Andrew; Hsieh, Shulan

    2014-01-01

    In task-switching paradigms, performance is better when repeating the same task than when alternating between tasks (switch cost) and when repeating a task alone rather than intermixed with another task (mixing cost). These costs remain even after extensive practice and when task cues enable advanced preparation (residual costs). Moreover, residual reaction time mixing cost has been consistently shown to increase with age. Residual switch and mixing costs modulate the amplitude of the stimulu...

  8. Reactive control processes contributing to residual switch cost and mixing cost in young and old adults

    OpenAIRE

    FriniKarayanidis; ShulanHsieh; AndrewHeathcote

    2014-01-01

    In task-switching paradigms, performance is better when repeating the same task than when alternating between tasks (switch cost) and when repeating a task alone rather than intermixed with another task (mixing cost). These costs remain even after extensive practice and when task cues enable advanced preparation (residual costs). Moreover, residual RT mixing cost has been consistently shown to increase with age. Residual switch and mixing costs modulate the amplitude of the stimulus-locked P3...

  9. Interaction of excitation and inhibition in processing of pure tone and amplitude-modulated stimuli in the medial superior olive of the mustached bat.

    Science.gov (United States)

    Grothe, B

    1994-02-01

    1. In mammals with good low-frequency hearing, the medial superior olive (MSO) processes interaural time or phase differences that are important cues for sound localization. Its cells receive excitatory projections from both cochlear nuclei and are thought to function as coincidence detectors. The response patterns of MSO neurons in most mammals are predominantly sustained. In contrast, the MSO in the mustached bat is a monaural nucleus containing neurons with phasic discharge patterns. These neurons receive projections from the contralateral anteroventral cochlear nucleus (AVCN) and the ipsilateral medial nucleus of the trapezoid body (MNTB). 2. To further investigate the role of the MSO in the bat, the responses of 252 single units in the MSO to pure tones and sinusoidal amplitude-modulated (SAM) stimuli were recorded. The results confirmed that the MSO in the mustached bat is tonotopically organized, with low frequencies in the dorsal part and high frequencies in the ventral part. The 61-kHz region is overrepresented. Most neurons tested (88%) were monaural and discharged only in response to contralateral stimuli. Their response could not be influenced by stimulation of the ipsilateral ear. 3. Only 11% of all MSO neurons were spontaneously active. In these neurons the spontaneous discharge rate was suppressed during the stimulus presentation. 4. The majority of cells (85%) responded with a phasic discharge pattern. About one-half (51%) responded with a level-independent phasic ON response. Other phasic response patterns included phasic OFF or phasic ON-OFF, depending on the stimulus frequency. Neurons with ON-OFF discharge patterns were most common in the 61-kHz region and absent in the high-frequency region. 5. Double tone experiments showed that at short intertone intervals the ON response to the second stimulus or the OFF response to the first stimulus was inhibited. 6. In neuropharmacological experiments, glycine applied to MSO neurons (n = 71) inhibited any tone-evoked response. In the presence of the glycine antagonist strychnine the response patterns changed from phasic to sustained (n = 35) and the neurons responded to both tones presented in double tone experiments independent of the intertone interval (n = 5). The effects of strychnine were reversible. 7. Twenty of 21 neurons tested with sinusoidally amplitude-modulated (SAM) signals exhibited low-pass or band-pass filter characteristics. Tests with SAM signals also revealed a weak temporal summation of inhibition in 13 of the 21 cells tested.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8176433

  10. Dosimetric implications of residual seminal vesicle motion in fiducial-guided intensity-modulated radiotherapy for prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Stenmark, Matthew H.; Vineberg, Karen; Ten Haken, Randall K.; Hamstra, Daniel A. [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Feng, Mary, E-mail: maryfeng@med.umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States)

    2012-10-01

    To determine whether residual interfraction seminal vesicle (SV) displacement necessitates specific planning target volume (PTV) margins during fiducial-guided intensity modulated radiation therapy (IMRT) of the prostate. A planning computed tomography (CT) scan and 2 subsequent CT scans were prospectively obtained for 20 prostate cancer patients with intraprostatic fiducial markers. After CT registration, SV displacement relative to the prostate was quantified as a function of margin size for both the proximal (1 cm) SV (PSV) and the full SV (FSV). Two IMRT plans were simulated for each patient (prostate + PSV and prostate + FSV) both with a uniform 5-mm PTV margin. Minimum clinical target volume (CTV) dose (D{sub min}) and the volume of SV receiving 95% of the prescription dose (V{sub 95%}) were assessed during treatment and compared with the initial plan. In all cases, SV displacement with respect to the prostate was greater for the FSV compared with the PSV. To ensure at least 95% geometrical coverage of the CTV for 90% of patients, margins of 5 and 8 mm were required for the PSV and FSV, respectively. Dosimetrically, residual SV displacement had minimal impact on PSV coverage compared with FSV coverage. For the PSV D{sub min} was {>=}95% of the prescribed dose in 90% of patients with an overall mean V{sub 95%} of 99.6 {+-} 0.8%; for the FSV D{sub min} was {>=}95% of the prescribed dose in only 45% of patients with a mean V{sub 95%} of 97.9 {+-} 2.4%. The SVs move differentially from the prostate and exhibit greater variation with increasing distance from the prostate. For plans targeting just the prostate and PSVs, 5-mm PTV expansions are adequate. However, despite daily localization of the prostate, larger PTV margins are required for cases where the intent is to completely cover the FSV.

  11. Dosimetric implications of residual seminal vesicle motion in fiducial-guided intensity-modulated radiotherapy for prostate cancer

    International Nuclear Information System (INIS)

    To determine whether residual interfraction seminal vesicle (SV) displacement necessitates specific planning target volume (PTV) margins during fiducial-guided intensity modulated radiation therapy (IMRT) of the prostate. A planning computed tomography (CT) scan and 2 subsequent CT scans were prospectively obtained for 20 prostate cancer patients with intraprostatic fiducial markers. After CT registration, SV displacement relative to the prostate was quantified as a function of margin size for both the proximal (1 cm) SV (PSV) and the full SV (FSV). Two IMRT plans were simulated for each patient (prostate + PSV and prostate + FSV) both with a uniform 5-mm PTV margin. Minimum clinical target volume (CTV) dose (Dmin) and the volume of SV receiving 95% of the prescription dose (V95%) were assessed during treatment and compared with the initial plan. In all cases, SV displacement with respect to the prostate was greater for the FSV compared with the PSV. To ensure at least 95% geometrical coverage of the CTV for 90% of patients, margins of 5 and 8 mm were required for the PSV and FSV, respectively. Dosimetrically, residual SV displacement had minimal impact on PSV coverage compared with FSV coverage. For the PSV Dmin was ?95% of the prescribed dose in 90% of patients with an overall mean V95% of 99.6 ± 0.8%; for the FSV Dmin was ?95% of the prescribed dose in only 45% of patients with a mean V95% of 97nts with a mean V95% of 97.9 ± 2.4%. The SVs move differentially from the prostate and exhibit greater variation with increasing distance from the prostate. For plans targeting just the prostate and PSVs, 5-mm PTV expansions are adequate. However, despite daily localization of the prostate, larger PTV margins are required for cases where the intent is to completely cover the FSV.

  12. Phase and amplitude stabilization of superconducting resonators

    International Nuclear Information System (INIS)

    The problem of phase and amplitude stabilization of the fields in superconducting resonators is described. The problem arises from the fast (approx. 50 Hz) resonator eigenfrequency modulation of magnitude (approx. 100 Hz) which is much larger than the resonator bandwidth (approx. 10 Hz). The problem is compounded by the fact that the coupling between the electrical and mechanical modes of the resonator can lead to instabilities (ponderomotive instabilities). The solution suggested involves operating the resonators in self-excited loops, and electronically modifying the loop parameters in order to lock the loop oscillations to an external phase and amplitude reference without attempt to modify the instantaneous resonator eigenfrequency. It is found that this method of phase stabilization is well suited to resonators with small energy contents and small eigenfrequency deviations since the power required is equal to their product; this occurs when the loaded bandwidth of the resonator is twice the maximum eigenfrequency deviation to be compensated for. It is also found that when the loop is free-running, the field amplitude is stable and no ponderomotive instabilities are present as long as the non-ideal effects are limited. When the loop is locked to an external phase and amplitude reference, ponderomotive instabilities can occur; however, the loop can be made stable by adjustment of the loop phase shift, and the stable range can be increased by using high amplitude andn be increased by using high amplitude and phase feedback gains. It is also found that under certain feedback conditions, the error on the particle energy gain can be made to vanish, although residual phase and amplitude errors are still present. A microprocessor-controlled feedback system based on this analysis is then described and results of experiments performed in conjunction with a 150 MHz lead (Pb) plated superconducting split-ring resonator are presented. The experiments show excellent agreement with the analysis

  13. Microstructure and roughness of photopolymerized poly(ethylene glycol) diacrylate hydrogel as measured by atomic force microscopy in amplitude and frequency modulation mode

    Energy Technology Data Exchange (ETDEWEB)

    Munz, M., E-mail: martin.munz@npl.co.uk

    2013-08-15

    In this study, atomic force microscopy (AFM) has been employed to image a photopolymerized poly(ethylene glycol) diacrylate (PEG-DA) hydrogel. The same area was imaged both in amplitude modulation (AM) and in frequency modulation (FM) mode and the latter allowed for excellent resolution of the hydrogel microstructure. It shows globular domains with typical diameters in the range of ?10–100 nm. The hydrogel morphology has been analysed using grain size analysis as well as roughness analysis. Based on AFM topography images of hydrogel nano-domains, a set of roughness parameters has been identified which can be readily used as descriptors for spatial resolution. It includes the density of summits, S{sub ds}, the mean summit curvature, S{sub sc}, the surface area ratio, S{sub dr}, and the correlation length parameter, S{sub cl37}. The latter describes the length over which the autocorrelation function decays to 37% of its peak value. These parameters allow for better discrimination than the widely used root-mean-square (RMS) roughness, S{sub q}, and are available with common image processing software packages. Systematic variation of the virtual tilt angle has indicated that these parameters are robust to small variations in plane levelling. Such image processing is frequently needed to separate the inherent surface microstructure from the global topography related to sample tilt or surface waviness. Hydrogels are an important group of biomaterials as they find numerous applications in biomedical engineering, ranging from adhesives, to controlled release of water-soluble drugs, to encapsulation of cells, to tissue engineering. Optimisation of their interactions with bioentities, such as bacteria, cells or proteins, requires accurate surface characterisation.

  14. Intensity modulated radiotherapy (IMRT) for recurrent, residual, or untreated skull-base meningiomas: preliminary clinical experience

    International Nuclear Information System (INIS)

    Objective: To investigate the feasibility of using intensity modulated radiotherapy (IMRT) for complex-shaped benign meningiomas of the skull base and report clinical experience. Methods: Twenty patients with benign skull-base meningiomas WHO degree sign I (histopathologically proven in 16/20) were treated with IMRT between June 1998 and August 1999. Each tumor was complex in shape and adherent to, or encompassed, organs at risk (cranial nerves, optic apparatus, and brainstem). All patients, immobilized in a customized head mask integrated into a stereotactic system, were planned on an inverse treatment planning system using 5 or 7 coplanar, equidistant beams and 5 intensity steps. Each treatment plan was verified extensively before treatment. Follow-up with MRI and clinical examination was performed at 6 and 18 weeks and every 6 months thereafter. Results: Target volumes ranged from 27 to 278 cc (median: 108 cc). Mean dose in 32 fractions ranged between 55.8 and 58.2 Gy. At median follow-up of 36 months (range: 31-43 months), pre-existing neurologic symptoms improved in 12/20 (60%), remained stable in 7/20 (35%), and worsened in 1 (5%) patient. Radiographic follow-up revealed significant tumor shrinkage 6 weeks post-IMRT in 2 patients and partial remission in 3 more patients at 9-17 months; other tumor volumes remained stable. There was no radiation-induced peritumoral edema, increase in tumor size, or new onset of neurologic deficits. Transient acute treatment side deficits. Transient acute treatment side effects included nausea and vomiting and single occurrences of conjunctivitis/increased tearing and serous tympanitis. Conclusion: IMRT in the treatment of central nervous system meningiomas is feasible and safe, offering highly conformal irradiation for complex-shaped skull-base tumors while sparing adjacent critical structures. If the tumor remissions seen here are found in the ongoing treatments, IMRT may be considered the treatment of choice for inoperable or subtotally resected meningiomas and for otherwise difficult-to-treat, complex-shaped tumors of the central nervous system adjacent to critical structures, with the potential of dose escalation for malignant tumors

  15. SAR impulse response with residual chirps.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2009-06-01

    A Linear Frequency-Modulated (LFM) chirp is a function with unit amplitude and quadratic phase characteristic. In a focused Synthetic Aperture Radar (SAR) image, a residual chirp is undesired for targets of interest, as it coarsens the manifested resolution. However, for undesired spurious signals, a residual chirp is often advantageous because it spreads the energy and thereby diminishes its peak value. In either case, a good understanding of the effects of a residual LFM chirp on a SAR Impulse Response (IPR) is required to facilitate system analysis and design. This report presents an analysis of the effects of a residual chirp on the IPR. As reference, there is a rich body of publications on various aspects of LFM chirps. A quick search reveals a plethora of articles, going back to the early 1950s. We mention here purely as trivia one of the earlier analysis papers on this waveform by Klauder, et al.

  16. A model of anuran auditory periphery reveals frequency-dependent adaptation to be a contributing mechanism for two-tone suppression and amplitude modulation coding.

    Science.gov (United States)

    Wotton, J M; Ferragamo, M J

    2011-10-01

    Anuran auditory nerve fibers (ANF) tuned to low frequencies display unusual frequency-dependent adaptation which results in a more phasic response to signals above best frequency (BF) and a more tonic response to signals below. A network model of the first two layers of the anuran auditory system was used to test the contribution of this dynamic peripheral adaptation on two-tone suppression and amplitude modulation (AM) tuning. The model included a peripheral sandwich component, leaky-integrate-and-fire cells and adaptation was implemented by means of a non-linear increase in threshold weighted by the signal frequency. The results of simulations showed that frequency-dependent adaptation was both necessary and sufficient to produce high-frequency-side two-tone suppression for the ANF and cells of the dorsal medullary nucleus (DMN). It seems likely that both suppression and this dynamic adaptation share a common mechanism. The response of ANFs to AM signals was influenced by adaptation and carrier frequency. Vector strength synchronization to an AM signal improved with increased adaptation. The spike rate response to a carrier at BF was the expected flat function with AM rate. However, for non-BF carrier frequencies the response showed a weak band-pass pattern due to the influence of signal sidebands and adaptation. The DMN received inputs from three ANFs and when the frequency tuning of inputs was near the carrier, then the rate response was a low-pass or all-pass shape. When most of the inputs were biased above or below the carrier, then band-pass responses were observed. Frequency-dependent adaptation enhanced the band-pass tuning for AM rate, particularly when the response of the inputs was predominantly phasic for a given carrier. Different combinations of inputs can therefore bias a DMN cell to be especially well suited to detect specific ranges of AM rates for a particular carrier frequency. Such selection of inputs would clearly be advantageous to the frog in recognizing distinct spectral and temporal parameters in communication calls. PMID:21565263

  17. On cruel mistakes in the calculation of multi-loop superstring amplitudes, the ambiguity of the modular integral and the integration over the module space

    CERN Document Server

    Danilov, G S

    2003-01-01

    Widely spread cruel misconceptions and mistakes in the calculation of multi-loop superstring amplitudes are exposed. Correct calculations are given. It is shown that the cardinal mistake in the gauge fixing procedure presents ab ovo in the Verlinde papers. The mistake was reproduced in following proposals including the recent papers. The modular symmetry of the multi-loop superstring amplitudes is clarified, an incorrectness of previous conjectures being shown. It is shown that the Berezin-type integral versus boson and fermion moduli is doubt under non-split transformations mixing fermion integration variables to the boson integration ones. In particular, due to singularities in moduli of the given spin structure, the integral can be finite or divergent dependently on the integration variables employed. Hence, unlike naive expectations, the multi-loop superstring amplitude is ambiguous. Nevertheless, the ambiguity is totally resolved by the requirement to preserve local symmetries of the superstring amplitud...

  18. Modulating Native-like Residual Structure in the Fully Denatured State of Photoactive Yellow Protein Affects Its Refolding*

    OpenAIRE

    Lee, Byoung-chul; Kumauchi, Masato; Hoff, Wouter D.

    2010-01-01

    Residual structure in the fully unfolded state is a key element for understanding protein folding. We show that the residual structure in fully denatured photoactive yellow protein (PYP) is affected by isomerization of its p-coumaric acid (pCA) chromophore. The exposure of total surface area and hydrophobic surface area upon unfolding was quantified by denaturant m values and heat capacity changes (?Cp), respectively. The exposure of the buried surface area upon the unfolding of the acid-den...

  19. P3-P3' residues flanking scissile bonds in factor VIII modulate rates of substrate cleavage and procofactor activation by thrombin.

    Science.gov (United States)

    Newell-Caito, Jennifer L; Griffiths, Amy E; Fay, Philip J

    2012-04-24

    Thrombin-catalyzed activation of factor VIII (FVIII) occurs through proteolysis at three P1 Arg residues: Arg(372) and Arg(740) in the FVIII heavy chain and Arg(1689) in the FVIII light chain. Cleavage at the latter two sites is relatively fast compared with cleavage at Arg(372), which appears to be rate-limiting. Examination of the P3-P3' residues flanking each P1 site revealed that those sequences at Arg(740) and Arg(1689) are more optimal for thrombin cleavage than at Arg(372), suggesting these sequences may impact reaction rates. Recombinant FVIII variants were prepared with mutations swapping scissile bond flanking sequences in the heavy chain individually and in combination with a second swap or with a P1 point mutation. Rates of generation of A1 and A3-C1-C2 subunits were determined by Western blotting and correlated with rates of cleavage at Arg(372) and Arg(1689), respectively. Rates of thrombin cleavage at Arg(372) were increased ~10- and ~3-fold compared with that of wild-type FVIII when it was replaced with P3-P3' residues flanking Arg(740) and Arg(1689), respectively, and these values paralleled increased rates of A2 subunit generation and procofactor activation. Positioning of more optimal residues flanking Arg(372) abrogated the need for initial cleavage at Arg(740) to facilitate this step. These results show marked changes in cleavage rates correlate with the extent of cleavage-optimal residues flanking the scissile bond and modulate the mechanism for procofactor activation. PMID:22455313

  20. Quadrature amplitude modulation from basics to adaptive trellis-coded turbo-equalised and space-time coded OFDM CDMA and MC-CDMA systems

    CERN Document Server

    Hanzo, Lajos

    2004-01-01

    "Now fully revised and updated, with more than 300 pages of new material, this new edition presents the wide range of recent developments in the field and places particular emphasis on the family of coded modulation aided OFDM and CDMA schemes. In addition, it also includes a fully revised chapter on adaptive modulation and a new chapter characterizing the design trade-offs of adaptive modulation and space-time coding." "In summary, this volume amalgamates a comprehensive textbook with a deep research monograph on the topic of QAM, ensuring it has a wide-ranging appeal for both senior undergraduate and postgraduate students as well as practicing engineers and researchers."--Jacket.

  1. Experimental study on MOSFET pulse modulator

    International Nuclear Information System (INIS)

    The design of the trigger based on complex programmable logic device (CPLD), the driver circuit and the residual current device (RCD) circuit of MOSFT pulse modulator were introduced, and the parallel-switch and inductive-adder MOSFET modulators were experimentally studied. The push-pull output circuit made up to a pair of MOSFETs was used in the driver circuit. The Pspice simulation results indicated that the peak inverse voltage on MOSFET switch could be clamped by RCD. A pulse current with an amplitude of 13 A, a rise time of 20 ns and a flat top time of 80 ns was obtained on the load of 30 ? when 3 parallel MOSFET modulator was adopted as the switch and the charge voltage was 450 V, while the amplitude of the obtained pulse was 40 A, the rise time 25 ns and flat top time 70 ns on the load of 30 ? when the inductive adder modulator was adopted. (authors)

  2. An atypical residue in the pore of Varroa destructor GABA-activated RDL receptors affects picrotoxin block and thymol modulation

    OpenAIRE

    Price, Kerry L.; Lummis, Sarah C. R.

    2014-01-01

    GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using ...

  3. Posttranslational Nitration of Tyrosine Residues Modulates Glutamate Transmission and Contributes to N-Methyl-D-aspartate-Mediated Thermal Hyperalgesia

    OpenAIRE

    Carolina Muscoli; Concetta Dagostino; Sara Ilari; Filomena Lauro; Micaela Gliozzi; Erlisa Bardhi; Ernesto Palma; Vincenzo Mollace; Daniela Salvemini

    2013-01-01

    Activation of the N-methyl-D-aspartate receptor (NMDAR) is fundamental in the development of hyperalgesia. Overactivation of this receptor releases superoxide and nitric oxide that, in turn, forms peroxynitrite (PN). All of these events have been linked to neurotoxicity. The receptors and enzymes involved in the handling of glutamate pathway—specifically NMDARs, glutamate transporter, and glutamine synthase (GS)—have key tyrosine residues which are targets of the nitration process causing...

  4. Residues in the 5th module of the low-density lipoprotein receptor that bind apoE and apoB-100

    International Nuclear Information System (INIS)

    Full text: The low-density lipoprotein receptor (LDLR) binds and removes cholesterol-rich lipoproteins from the circulation. Its ligand-binding (LB) domain consists of seven cysteine-rich LB modules that bind apoB-100 and apoE. These modules fold into well-defined structures with three disulfide bonds, in the presence of Ca2+. The 5th module (LB5) is unique in that it is required to bind both apoB-100 and apoE. The aim of the current study was to map residues in human LB5 that are required for ligand binding. This was done by alanine mutagenesis of a series of residues that are conserved in human, mouse, rat and rabbit LB5 (E9, S14, E16, H19, S21, K31, and K33), but not in the other six modules. E37 (R37 in the rabbit) was included, since it has been previously hypothesized to play a role in binding. The variant LB5 modules were first produced as recombinant peptides, and subjected to oxidative folding to determine whether the mutations interfered with Ca2+'-dependent folding. Only the S14A and E16A mutations interfered significantly with folding, suggesting that S14 and E16 are required for the structural framework of LB5 and that their substitution in the LDLR may interfere with its folding. The native LDLR and E9A, H19A, S21A, K31A, K33A and E37A LDLRs were expressed in LDLR negative IdlA-7 CHO cells. Labeling with 125I-lgG-C7 showed that all receptors were expressed on the cell surface. Binding of Dil-labeled LDL (Dil-LDL) and Dil-ding of Dil-labeled LDL (Dil-LDL) and Dil-labeled DMPC, complexed with the N-terminal receptor-binding domain of apoE3 (Dil-E3), at 4 deg C, was used to assess receptor binding. Binding of Dil-E3 (0.1 ?/ml) to the H19A, S21A, K31A, K33A and E37A LDLRs was 65-92% of binding to the native LDLR. In contrast, the E9A LDLR only bound 3% of that of the native LDLR. The binding of Dil-LDL (0.5 Ag/ml) to the E9A LDLR was 23% of that of the native LDLR, while binding to the remaining variant LDLRs ranged from 44-70% of what of the native LDLR. We conclude that (i) E9 of LB5 plays a key role in the binding of apoE and LDL, consistent with ionic interactions with basic residues on apoE and apoB-100. (ii) that H19, S21, K31, and K33 and E37 play a minor role in binding apoE, and (iii) that these residues play a small, but significant role in the binding of LDL

  5. Modulating the pH-activity profile of cellulase A from Cellulomonas fimi by replacement of surface residues.

    Science.gov (United States)

    Cockburn, Darrell W; Clarke, Anthony J

    2011-05-01

    One industrial process for the production of cellulosic ethanol and or value-added products involves exposing the cellulose content of plant materials by steam explosion in the presence of strong acid, followed by its neutralization and subsequent digestion with a cocktail of cellulolytic enzymes. These enzymes typically have activity optima at slightly acidic or neutral pH and so generating enzymes that are more active and tolerant in more acidic conditions would help to reduce associated costs. Here, we describe the engineering of cellulase A from Cellulomonas fimi as a model to replace residues that were identified as potentially influencing the pH-activity profile of the enzyme based on sequence alignments and analysis of the known three-dimensional structures of other CAZy family 6 glycoside hydrolases with the aim to lower its pH optimum. Twelve specific residues and a sequence of eight were identified and a total of 30 mutant enzymes were generated. In addition to being replaced with natural amino acids, some of the identified residues were substituted with cysteine and subsequently oxidized to cysteinesulfinate. Of the four single amino acid replacements that produced enhancements of activity at acidic pH, three involved the removal of charged groups from the surface of the enzyme. The generation of double mutations provided mixed results but the combination of Glu407 ? Ala and Tyr321 ? Phe replacements had an additive effect on the enhancement, reaching a total activity that was 162% of the wild-type level. This study thus illustrated the utility of altering the surface charge properties of the family 6 glycoside hydrolases to enhance activity at low pH and thereby an avenue for further protein engineering. PMID:21273341

  6. The structure of Bcl-w reveals a role for the C-terminal residues in modulating biological activity

    OpenAIRE

    Hinds, Mark G.; Lackmann, Martin; Skea, Gretchen L.; Harrison, Penny J.; Huang, David C. S.; Day, Catherine L.

    2003-01-01

    Pro-survival Bcl-2-related proteins, critical regulators of apoptosis, contain a hydrophobic groove targeted for binding by the BH3 domain of the pro-apoptotic BH3-only proteins. The solution structure of the pro-survival protein Bcl-w, presented here, reveals that the binding groove is not freely accessible as predicted by previous structures of pro-survival Bcl-2-like molecules. Unexpectedly, the groove appears to be occluded by the C-terminal residues. Binding and kinetic data suggest that...

  7. A new influenza virus virulence determinant: The NS1 protein four C-terminal residues modulate pathogenicity

    OpenAIRE

    Jackson, David; Hossain, Md Jaber; Hickman, Danielle; Perez, Daniel R.; Lamb, Robert A.

    2008-01-01

    The virulence of influenza virus is a multigenic trait. One determinant of virulence is the multifunctional NS1 protein that functions in several ways to defeat the cellular innate immune response. Recent large-scale genome sequence analysis of avian influenza virus isolates indicated that four C-terminal residues of the NS1 protein is a PDZ ligand domain of the X-S/T-X-V type and it was speculated that it may represent a virulence determinant. To test this hypothesis, by using mice as a mode...

  8. A single mutation in the 729 residue modulates human DNA topoisomerase IB DNA binding and drug resistance

    OpenAIRE

    Losasso, Carmen; Cretaio, Erica; Fiorani, Paola; D’annessa, Ilda; Chillemi, Giovanni; Benedetti, Piero

    2008-01-01

    Human DNA topoisomerase I (hTop1p) catalyzes the relaxation of supercoiled DNA and constitutes the cellular target of the antitumor drug camptothecin (CPT). The X-ray crystal structure of the enzyme covalently joined to DNA and bound to the CPT analog Topotecan suggests that there are two classes of mutations that can produce a CPT-resistant enzyme. The first class includes changes in residues that directly interact with the drug, whereas a second class alters interactions with the DNA and th...

  9. Human Cannabinoid 2 GPCR Ligand-interaction Landscape: Cysteine Residues Critical to Biarylpyrazole Antagonist Binding Motif and Receptor Modulation

    OpenAIRE

    Mercier, Richard W.; Pei, Ying; Pandarinathan, Lakshmipathi; Janero, David R.; Zhang, Jing; Makriyannis, Alexandros

    2010-01-01

    The human cannabinoid 2 GPCR (hCB2) is a prime therapeutic target. To define potential cysteine-related binding motifs critical to hCB2-ligand interaction, a library of hCB2 cysteine-substitution mutants and a novel, high-affinity biarylpyrazole hCB2 inverse agonist (AM1336) functionalized to serve as a covalent affinity probe to target cysteine residues within (or in the microenvironment of) its hCB2 binding pocket were generated. The data provide direct experimental demonstration that both ...

  10. Effect of interferential current of different amplitude-modulated frequencies, on threshold and number of accommodations on healthy painless individuals / Efeito da corrente interferencial de diferentes frequências moduladas pela amplitude no limiar e número de acomodações em indivíduos saudáveis sem dor

    Scientific Electronic Library Online (English)

    Beatriz Gavassa de, Araújo; Karina Maria, Filipin; Tathiane, Pasqualli; Lucinéia de Fátima Chasko, Ribeiro; Gladson Ricardo Flor, Bertolini.

    2014-12-01

    Full Text Available JUSTIFICATIVA E OBJETIVOS: Apesar do uso generalizado da corrente interferencial, há controvérsias na literatura sobre os parâmetros ideais de estimulação utilizados. O objetivo deste estudo foi avaliar o limiar e o número total de acomodações em indivíduos estimulados por diferentes frequências mo [...] duladas pela amplitude. MÉTODOS: Trata-se de um ensaio clínico, cruzado, com amostra de conveniência aleatorizada e encoberta, composta por 20 indivíduos saudáveis, com idade média de 20,35 anos, de ambos os gêneros. Os voluntários foram submetidos a corrente interferencial por 20 minutos, na forma bipolar, com os eletrodos localizados na articulação do cotovelo, sendo posicionados um sobre a superficialidade do nervo ulnar e outro do nervo mediano. Os parâmetros do equipamento foram: frequência base de 4.000Hz, frequências moduladas pela amplitude de 1, 10 ou 100Hz (de acordo com o subgrupo do dia). Foi avaliado o limiar de acomodação e o número total de acomodações. RESULTADOS: Para o limiar de acomodação não foram encontradas diferenças significativas (p>0,05); quanto ao número de acomodações houve diferenças significativas entre as frequências de 10 e 100Hz (p Abstract in english BACKGROUND AND OBJECTIVES: Despite the widespread use of interferential current, controversy exists in the literature on the optimal stimulation parameters. The aim of this study was to evaluate the threshold and the total number of accommodations in subjects stimulated by different amplitude-modul [...] ated frequencies. METHODS: The study is a clinical, cross-over trial with randomized and blinded convenience sample consisted of 20 healthy subjects, with mean age of 20.35 years, of both genders. Volunteers underwent interferential current for 20 minutes, the bipolar form, with electrodes placed on the elbow joint being positioned one above the superficiality of the ulnar nerve and the other of the median nerve. Equipment parameters were: base frequency of 4,000Hz, amplitude-modulated frequencies 1, 10 or 100Hz (according to the subgroup). Threshold and total number of accommodations were assessed. RESULTS: For the accommodation threshold no significant differences were found (p>0.05). With regard to the number of accommodations, there have been significant differences between the frequencies of 10 and 100Hz (p

  11. External pH modulates EAG superfamily K+ channels through EAG-specific acidic residues in the voltage sensor.

    Science.gov (United States)

    Kazmierczak, Marcin; Zhang, Xiaofei; Chen, Bihan; Mulkey, Daniel K; Shi, Yingtang; Wagner, Paul G; Pivaroff-Ward, Kendra; Sassic, Jessica K; Bayliss, Douglas A; Jegla, Timothy

    2013-06-01

    The Ether-a-go-go (EAG) superfamily of voltage-gated K(+) channels consists of three functionally distinct gene families (Eag, Elk, and Erg) encoding a diverse set of low-threshold K(+) currents that regulate excitability in neurons and muscle. Previous studies indicate that external acidification inhibits activation of three EAG superfamily K(+) channels, Kv10.1 (Eag1), Kv11.1 (Erg1), and Kv12.1 (Elk1). We show here that Kv10.2, Kv12.2, and Kv12.3 are similarly inhibited by external protons, suggesting that high sensitivity to physiological pH changes is a general property of EAG superfamily channels. External acidification depolarizes the conductance-voltage (GV) curves of these channels, reducing low threshold activation. We explored the mechanism of this high pH sensitivity in Kv12.1, Kv10.2, and Kv11.1. We first examined the role of acidic voltage sensor residues that mediate divalent cation block of voltage activation in EAG superfamily channels because protons reduce the sensitivity of Kv12.1 to Zn(2+). Low pH similarly reduces Mg(2+) sensitivity of Kv10.1, and we found that the pH sensitivity of Kv11.1 was greatly attenuated at 1 mM Ca(2+). Individual neutralizations of a pair of EAG-specific acidic residues that have previously been implicated in divalent block of diverse EAG superfamily channels greatly reduced the pH response in Kv12.1, Kv10.2, and Kv11.1. Our results therefore suggest a common mechanism for pH-sensitive voltage activation in EAG superfamily channels. The EAG-specific acidic residues may form the proton-binding site or alternatively are required to hold the voltage sensor in a pH-sensitive conformation. The high pH sensitivity of EAG superfamily channels suggests that they could contribute to pH-sensitive K(+) currents observed in vivo. PMID:23712551

  12. Halquinol modulated growth, physiology, and protein profile and halquinol residue withdrawal study in the Indian major carp Catla catla (Hamilton).

    Science.gov (United States)

    Mushigeri, S B; Saha, S; Somashekar, B N; Nischal, K; Radhakrishna, P M

    2008-01-01

    The aim of the present study was to evaluate the effect of halquinol, an antimicrobial used as a growth promotor in poultry, on the fresh water fish Catla catla in terms of growth promotion, protein profile, and physiology as the rate of oxygen consumption. A synergic increment in the free amino acid level and total protein concentration suggested enhanced anabolic metabolism resulting in weight gain. When compared with an untreated control group, fishes treated with 0.1% halquinol (T1) showed a higher weight gain than those treated with 0.2% halquinol (T2). Variations in the rate of oxygen consumption among the three groups (control, T1, T2) expressed the physiological response of the animals toward the chemical along the time factor. After 7 days of treatment, the absence of halquinol revealed by post-withdrawal residual HPLC studies suggests its biosafety. PMID:19024792

  13. Higher rank cylinder amplitude

    International Nuclear Information System (INIS)

    The dual topological unitarization is investigated for the case of any number of planar SU(N) singlet reggeons. In particular, the detailed structure of the cylinder amplitude is fully investigated. The planar bootstrap constraints are derived for the reggeon propagator and the triple reggeon vertex. The cylinder unitarization of planar poles is performed by means of the planar sewing method. The cylinder equation is described in terms of the factorizable kernel of finite rank. We are then led to the following typical properties of the cylinder. First, the cylinder partial wave amplitude is meromorphic in the J-plane. Secondly, extinction of the input SU(N) singlets is guaranteed. Thirdly, the cylinder residue is factorizable at all t. Fourthly, the cylindrical mixing is inevitable for the higher rank kernel. Moreover, the mixing phenomena are examined for the special case of the single daughter contribution. The repulsive [attractive] mixing pattern is expected to be observed between the even [odd] charge conjugation components of the cylindrically renormalized trajectories in the weak cylindrical mixing limit. (author)

  14. Higher Rank Cylinder Amplitude

    Science.gov (United States)

    Yang, S.

    1980-11-01

    The dual topological unitarization is investigated for the case of any number of planar SU(N) singlet reggeons. In particular, the detailed structure of the cylinder amplitude is fully investigated. The planar bootstrap constraints are derived for the reggeon propagator and the triple reggeon vertex. The cylinder unitarization of planar poles is performed by means of the planar sewing method. The cylinder equation is described in terms of the factorizable kernel of finite rank. We are then led to the following typical properties of the cylinder. First, the cylinder partial wave amplitude is meromorphic in the J-plane. Secondly, extinction of the input SU(N) singlets is guaranteed. Thirdly, the cylinder residue is factorizable at all t. Fourthly, the cylindrical mixing is inevitable for the higher rank kernel. Moreover, the mixing phenomena are examined for the special case of the single daughter contribution. The repulsive [attractive] mixing pattern is expected to be observed between the even [odd] charge conjugation components of the cylindrically renormalized trajectories in the weak cylindrical mixing limit.

  15. MASMA: a versatile multifunctional unit (gated window amplifier, analog memory, and height-to-time converter); Element multifonctionnel M.A.S.M.A. (module amplificateur a seuil, memoire analogique et convertisseur amplitude-temps)

    Energy Technology Data Exchange (ETDEWEB)

    Goursky, V.; Thenes, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    This multipurpose unit is designed to accomplish one of the following functions: - gated window amplifier, - Analog memory and - Amplitude-to-time converter. The first function is mainly devoted to improve the poor resolution of pulse-height analyzers with a small number of channels. The analog memory, a new function in the standard range of plug-in modules, is capable of performing a number of operations: 1) fixed delay, or variable delay dependent on an external parameter (application to the analog processing of non-coincident pulses), 2) de-randomiser to increase the efficiency of the pulse height analysis in a spectrometry experiment, 3) linear multiplexer to allow an analyser to serve as many spectrometry devices as memory elements that it possesses. Associated with a coding scaler, this unit, if used as a amplitude-to-time converter, constitutes a Wilkinson A.D.C with a capability of 10 bits (or more) and with a 100 MHz clock frequency. (authors) [French] Le present element est concu pour etre utilise dans l'un des modes de fonctionnement suivants: - amplificateur a seuil avec porte, - memoire analogique, - convertisseur amplitude-temps. La fonction amplificateur a seuil est destinee principalement a remedier a la resolution insuffisante de certains analyseurs d'amplitude possedant un faible nombre de canaux. La fonction memoire analogique est une fonction qui n'existe pas encore dans la gamme d'elements standardises. Elle peut trouver de nombreuses applications; a titre d'exemple, citons: 1) element de retard fixe ou dependant d'un parametre externe (application au calcul analogique portant sur les impulsions), 2) memoire-tampon: placee devant un analyseur, elle augmente l'efficacite d'analyse d'une chaine de spectrometrie, 3) multiplexeur analogique, permettant a un seul analyseur de desservir autant de voies de spectrometrie qu'il possede de memoires. En fonction convertisseur amplitude-temps, ce tiroir, associe a une echelle de codage, permet de realiser un analyseur numerique du type WILKINSON a 10 bits (ou plus) fonctionnant avec une frequence de 100 MHz. (auteur)

  16. Analysis of binding of the family 2a carbohydrate-binding module from Cellulomonas fimi xylanase 10A to cellulose: specificity and identification of functionally important amino acid residues.

    Science.gov (United States)

    McLean, B W; Bray, M R; Boraston, A B; Gilkes, N R; Haynes, C A; Kilburn, D G

    2000-11-01

    The family 2a carbohydrate-binding module (CBM2a) of xylanase 10A from Cellulomonas fimi binds to the crystalline regions of cellulose. It does not share binding sites with the N-terminal family 4 binding module (CBM4-1) from the cellulase 9B from C.fimi, a module that binds strictly to soluble sugars and amorphous cellulose. The binding of CBM2a to crystalline matrices is mediated by several residues on the binding face, including three prominent, solvent-exposed tryptophan residues. Binding to crystalline cellulose was analyzed by making a series of conservative (phenylalanine and tyrosine) and non-conservative substitutions (alanine) of each solvent-exposed tryptophan (W17, W54 and W72). Other residues on the binding face with hydrogen bonding potential were substituted with alanine. Each tryptophan plays a different role in binding; a tryptophan is essential at position 54, a tyrosine or tryptophan at position 17 and any aromatic residue at position 72. Other residues on the binding face, with the exception of N15, are not essential determinants of binding affinity. Given the specificity of CBM2a, the structure of crystalline cellulose and the dynamic nature of the binding of CBM2a, we propose a model for the interaction between the polypeptide and the crystalline surface. PMID:11161112

  17. Energy dissipation and dynamic response of an amplitude-modulation atomic-force microscopy subjected to a tip-sample viscous force.

    Science.gov (United States)

    Lin, Shueei Muh

    2007-01-01

    In a common environment of atomic force microscopy (AFM), a damping force occurs between a tip and a sample. The influence of damping on the dynamic response of a cantilever must be significant. Moreover, accurate theory is very helpful for the interpretation of a sample's topography and properties. In this study, the effects of damping and nonlinear interatomic tip-sample forces on the dynamic response of an amplitude-formulation AFM are investigated. The damping force is simulated by using the conventional Kelvin-Voigt damping model. The interatomic tip-sample force is the attractive van der Waals force. For consistance with real measurement of a cantilever, the mathematical equations of the beam theory of an AM-AFM are built and its analytical solution is derived. Moreover, an AFM system is also simplified into a mass-spring-damper model. Its exact solution is simple and intuitive. Several relations among the damping ratio, the response ratio, the frequency shift, the energy dissipation and the Q-factor are revealed. It is found that the resonant frequencies and the phase angles determined by the two models are almost same. Significant differences in the resonant quality factors and the response ratios determined by using the two models are also found. Finally, the influences of the variations of several parameters on the error of measuring a sample's topography are investigated. PMID:16982149

  18. Interpreting the large amplitude X-ray variation of GRS 1915+105 and IGR J17091-3624 as modulations of an accretion disc

    CERN Document Server

    Pahari, Mayukh; Mukherjee, Arunava; Yadav, J S; Pandey, S K

    2013-01-01

    Using the flux resolved spectroscopy for the first time, we analyse the RXTE/PCA data of the black hole X-ray binaries GRS 1915+105 and IGR J17091-3624, when both sources show large amplitude, quasi-regular oscillations in 2.0-60.0 keV X-ray light curves. For different observations, we extract spectra during the peak (spectrally soft) and dip (spectrally hard) intervals of the oscillation, and find that their spectra are phenomenologically complex, requiring at least two distinct spectral components. Besides a thermal Comptonization component, we find that the disc emission is better modelled by an index-free multicolour disc blackbody component (p-free disc model) rather than that from a standard accretion disc. While the peak and dip spectra are complex, remarkably, their difference spectra constructed by treating dip spectra as the background spectra of the peak spectra, can be modelled as a single p-free disc component. Moreover, the variability at different time-scales and energy bands of the peak flux l...

  19. Energy dissipation and dynamic response of an amplitude-modulation atomic-force microscopy subjected to a tip-sample viscous force

    International Nuclear Information System (INIS)

    In a common environment of atomic force microscopy (AFM), a damping force occurs between a tip and a sample. The influence of damping on the dynamic response of a cantilever must be significant. Moreover, accurate theory is very helpful for the interpretation of a sample's topography and properties. In this study, the effects of damping and nonlinear interatomic tip-sample forces on the dynamic response of an amplitude-formulation AFM are investigated. The damping force is simulated by using the conventional Kelvin-Voigt damping model. The interatomic tip-sample force is the attractive van der Waals force. For consistance with real measurement of a cantilever, the mathematical equations of the beam theory of an AM-AFM are built and its analytical solution is derived. Moreover, an AFM system is also simplified into a mass-spring-damper model. Its exact solution is simple and intuitive. Several relations among the damping ratio, the response ratio, the frequency shift, the energy dissipation and the Q-factor are revealed. It is found that the resonant frequencies and the phase angles determined by the two models are almost same. Significant differences in the resonant quality factors and the response ratios determined by using the two models are also found. Finally, the influences of the variations of several parameters on the error of measuring a sample's topography are investigated

  20. Role of active site residues and solvent in proton transfer and the modulation of flavin reduction potential in bacterial morphinone reductase.

    Science.gov (United States)

    Messiha, Hanan L; Bruce, Neil C; Sattelle, Benedict M; Sutcliffe, Michael J; Munro, Andrew W; Scrutton, Nigel S

    2005-07-22

    The reactions of several active site mutant forms of bacterial morphinone reductase (MR) with NADH and 2-cyclohexen-1-one as substrates have been studied by stopped-flow and steady-state kinetic methods and redox potentiometry. The enzymes were designed to (i) probe a role for potential proton donors (Tyr-72 and Tyr-356) in the oxidative half-reaction of MR; (ii) assess the function of a highly conserved tryptophan residue (Trp-106) in catalysis; (iii) investigate the role of Thr-32 in modulating the FMN reduction potential and catalysis. The Y72F and Y356F enzymes retained activity in both steady-state and stopped-flow kinetic studies, indicating they do not serve as key proton donors in the oxidative reaction of MR. Taken together with our recently published data (Messiha, H. L., Munro, A. W., Bruce, N. C., Barsukov, I., and Scrutton, N. S. (2005) J. Biol. Chem. 280, 4627-4631) that rule out roles for Cys-191 (corresponding with the proton donor, Tyr-196, in the structurally related OYE1 enzyme) and His-186 as proton donors, we infer solvent is the source of the proton in the oxidative half-reaction of MR. We demonstrate a key role for Thr-32 in modulating the reduction potential of the FMN, which is decreased approximately 50 mV in the T32A mutant MR. This effects a change in rate-limiting step in the catalytic cycle of the T32A enzyme with the oxidizing substrate 2-cyclohexenone. Despite the conservation of Trp-106 throughout the OYE family, we show this residue does not play a major role in catalysis, although affects on substrate and coenzyme binding are observed in a W106F enzyme. Our studies show some similarities, but also major differences, in the catalytic mechanism of MR and OYE1, and emphasize the need for caution in inferring mechanism by structural comparison of highly related enzymes in the absence of solution studies. PMID:15905167

  1. Scattering Amplitudes in Gauge Theories

    CERN Document Server

    Schubert, Ulrich

    2014-01-01

    This thesis is focused on the development of new mathematical methods for computing multi-loop scattering amplitudes in gauge theories. In this work we combine, for the first time, the unitarity-based construction for integrands, and the recently introduced integrand-reduction through multivariate polynomial division. After discussing the generic features of this novel reduction algorithm, we will apply it to the one- and two-loop five-point amplitudes in ${\\cal N}=4$ sYM. The integrands of the multiple-cuts are generated from products of tree-level amplitudes within the super-amplitudes formalism. The corresponding expressions will be used for the analytic reconstruction of the polynomial residues. Their parametric form is known a priori, as derived by means of successive polynomial divisions using the Gr\\"obner basis associated to the on-shell denominators. The integrand reduction method will be exploited to investigate the color-kinematic duality for multi-loop ${\\cal N}=4$ sYM scattering amplitudes. Our a...

  2. Cholinergic Blockade Reduces Theta-Gamma Phase Amplitude Coupling and Speed Modulation of Theta Frequency Consistent with Behavioral Effects on Encoding

    Science.gov (United States)

    Gillet, Shea N.; Climer, Jason R.; Hasselmo, Michael E.

    2013-01-01

    Large-scale neural activation dynamics in the hippocampal-entorhinal circuit local field potential, observable as theta and gamma rhythms and coupling between these rhythms, is predictive of encoding success. Behavioral studies show that systemic administration of muscarinic acetylcholine receptor antagonists selectively impairs encoding, suggesting that they may also disrupt the coupling between the theta and gamma bands. Here, we tested the hypothesis that muscarinic antagonists selectively disrupt coupling between theta and gamma. Specifically, we characterized the effects of systemically administered scopolamine on movement-induced theta and gamma rhythms recorded in the superficial layers of the medial entorhinal cortex (MEC) of freely moving rats. We report the novel result that gamma power at the peak of theta was most reduced following muscarinic blockade, significantly shifting the phase of maximal gamma power to occur at later phases of theta. We also characterize the existence of multiple distinct gamma bands in the superficial layers of the MEC. Further, we observed that theta frequency was significantly less modulated by movement speed following muscarinic blockade. Finally, the slope relating speed to theta frequency, a correlate of familiarity with a testing enclosure, increased significantly less between the preinjection and recovery trials when scopolamine was administered during the intervening injection session than when saline was administered, suggesting that scopolamine reduced encoding of the testing enclosure. These data are consistent with computational models suggesting that encoding and retrieval occur during the peak and trough of theta, respectively, and support the theory that acetylcholine regulates the balance between encoding versus retrieval. PMID:24336727

  3. Vesícula residual Residual gallbladder

    Directory of Open Access Journals (Sweden)

    Júlio C. U. Coelho

    2002-12-01

    Full Text Available Our objective is to report three patients with recurrent severe upper abdominal pain secondary to residual gallbladder. All patients had been subjected to cholecystectomy from 1 to 20 years before. The diagnosis was established after several episodes of severe upper abdominal pain by imaging exams: ultrasonography, tomography, or endoscopic retrograde cholangiography. Removal of the residual gallbladder led to complete resolution of symptoms. Partial removal of the gallbladder is a very rare cause of postcholecystectomy symptoms.

  4. Diode laser-frequency stabilization by use of frequency modulation by a vibrating mirror.

    Science.gov (United States)

    Mitsui, T; Yamashita, K; Sakurai, K

    1997-08-01

    Modulation of a laser frequency with a negligibly small residual amplitude modulation component has been demonstrated with a piezoelectric transducer-driven mirror. The vibrating-mirror method has been successfully applied to high-resolution spectroscopy of saturated absorption and to laser-frequency stabilization. The bandwidth of the stabilization feedback loop as wide as 15 kHz has been achieved to suppress acoustic noise in ordinary laboratory environment. PMID:18259371

  5. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire—KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

    International Nuclear Information System (INIS)

    The problem of the production of extended (?1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2–0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration (?100 ns), maintains the electron density at a level ne = (3–5) × 1014 cm—3 by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy (?0.5 eV) and a long lifetime (?1 ms), which are produced upon cessation of the laser pulse. (extreme light fields and their appllight fields and their applications)

  6. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire—KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

    Science.gov (United States)

    Zvorykin, V. D.; Ionin, Andrei A.; Levchenko, A. O.; Mesyats, Gennadii A.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, Igor V.; Sunchugasheva, E. S.; Ustinovskii, N. N.; Shutov, A. V.

    2013-04-01

    The problem of the production of extended (~1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2-0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration (~100 ns), maintains the electron density at a level ne = (3-5) × 1014 cm—3 by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy (~0.5 eV) and a long lifetime (~1 ms), which are produced upon cessation of the laser pulse.

  7. Crystallographic Studies of Prion Protein (PrP) Segments Suggest How Structural Changes Encoded by Polymorphism at Residue 129 Modulate Susceptibility to Human Prion Disease

    Energy Technology Data Exchange (ETDEWEB)

    Apostol, Marcin I.; Sawaya, Michael R.; Cascio, Duilio; Eisenberg, David (UCLA)

    2010-09-23

    A single nucleotide polymorphism (SNP) in codon 129 of the human prion gene, leading to a change from methionine to valine at residue 129 of prion protein (PrP), has been shown to be a determinant in the susceptibility to prion disease. However, the molecular basis of this effect remains unexplained. In the current study, we determined crystal structures of prion segments having either Met or Val at residue 129. These 6-residue segments of PrP centered on residue 129 are 'steric zippers,' pairs of interacting {beta}-sheets. Both structures of these 'homozygous steric zippers' reveal direct intermolecular interactions between Met or Val in one sheet and the identical residue in the mating sheet. These two structures, plus a structure-based model of the heterozygous Met-Val steric zipper, suggest an explanation for the previously observed effects of this locus on prion disease susceptibility and progression.

  8. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire-KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

    Energy Technology Data Exchange (ETDEWEB)

    Zvorykin, V D; Ionin, Andrei A; Levchenko, A O; Mesyats, Gennadii A; Seleznev, L V; Sinitsyn, D V; Smetanin, Igor V; Sunchugasheva, E S; Ustinovskii, N N; Shutov, A V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2013-04-30

    The problem of the production of extended ({approx}1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2-0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration ({approx}100 ns), maintains the electron density at a level n{sub e} = (3-5) Multiplication-Sign 10{sup 14} cm{sup -3} by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy ({approx}0.5 eV) and a long lifetime ({approx}1 ms), which are produced upon cessation of the laser pulse. (extreme light fields and their applications)

  9. Calculating scattering amplitudes efficiently

    International Nuclear Information System (INIS)

    We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs

  10. Finite amplitude envelope solitons

    International Nuclear Information System (INIS)

    A general theory of finite amplitude envelope Langmuir solitons is presented. Comparison with recent beam-plasma experiments suggests identification of the observed localized structures with these solitons

  11. Amplitudes, acquisition and imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bloor, Robert

    1998-12-31

    Accurate seismic amplitude information is important for the successful evaluation of many prospects and the importance of such amplitude information is increasing with the advent of time lapse seismic techniques. It is now widely accepted that the proper treatment of amplitudes requires seismic imaging in the form of either time or depth migration. A key factor in seismic imaging is the spatial sampling of the data and its relationship to the imaging algorithms. This presentation demonstrates that acquisition caused spatial sampling irregularity can affect the seismic imaging and perturb amplitudes. Equalization helps to balance the amplitudes, and the dealing strategy improves the imaging further when there are azimuth variations. Equalization and dealiasing can also help with the acquisition irregularities caused by shot and receiver dislocation or missing traces. 2 refs., 2 figs.

  12. P3-P3' Residues Flanking Scissile Bonds in Factor VIII Modulate Rates of Substrate Cleavage and Procofactor Activation by Thrombin†

    OpenAIRE

    Newell-caito, Jennifer L.; Griffiths, Amy E.; Fay, Philip J.

    2012-01-01

    Thrombin-catalyzed activation of factor VIII (FVIII) occurs through proteolysis at three P1 Arg residues: Arg372 and Arg740 in the FVIII heavy chain and Arg1689 in the FVIII light chain. Cleavage at the latter two sites is relatively fast compared with cleavage at Arg372, which appears rate limiting. Examination of the P3-P3? residues flanking each P1 site revealed that those sequences at Arg740 and Arg1689 are more optimal for thrombin cleavage than at Arg372, suggesting these sequences ma...

  13. Partial Regularity and Amplitude

    CERN Document Server

    Arapura, D

    2004-01-01

    This is a sequel to the paper "Frobenius amplitude and strong vanishing theorems for vector bundles" (math.AG/0202129). We introduce a more elementary variant of the notion of F-amplitude from the earlier paper which we call amplitude. This provides another measure of positivity of a vector bundle which is related to a number of preexisting positivity notions such as k-ampleness or q-convexity. We use this to refine the estimates of F-amplitude from the first paper, and to deduce some further vanishing theorems as a consequence. We also give some new proofs of some known vanishing theorems for Abelian and toric varieties by analogous methods. For technical reasons, we need to develop a theory of partial Castelnuovo-Mumford regularity which provides a rough measure of the cohomological complexity of a sheaf. Since this material may have independent interest, it is contained in a section which can be read on its own.

  14. Response maxima in modulated turbulence

    OpenAIRE

    Heydt, Anna Von; Grossmann, Siegfried; Lohse, Detlef

    2003-01-01

    Isotropic and homogeneous turbulence driven by an energy input modulated in time is studied within a variable range mean-field theory. The response of the system, observed in the second order moment of the large-scale velocity difference D(L,t)=~Re(t)^2$, is calculated for varying modulation frequencies w and weak modulation amplitudes. For low frequencies the system follows the modulation of the driving with almost constant amplitude, whereas for higher driving frequencies ...

  15. A naturally variable residue in the S1 subsite of M1 family aminopeptidases modulates catalytic properties and promotes functional specialization.

    Science.gov (United States)

    Dalal, Seema; Ragheb, Daniel R T; Schubot, Florian D; Klemba, Michael

    2013-09-01

    M1 family metallo-aminopeptidases fulfill a wide range of critical and in some cases medically relevant roles in humans and human pathogens. The specificity of M1-aminopeptidases is dominated by the interaction of the well defined S1 subsite with the side chain of the first (P1) residue of the substrate and can vary widely. Extensive natural variation occurs at one of the residues that contributes to formation of the cylindrical S1 subsite. We investigated whether this natural variation contributes to diversity in S1 subsite specificity. Effects of 11 substitutions of the S1 subsite residue valine 459 in the Plasmodium falciparum aminopeptidase PfA-M1 and of three substitutions of the homologous residue methionine 260 in Escherichia coli aminopeptidase N were characterized. Many of these substitutions altered steady-state kinetic parameters for dipeptide hydrolysis and remodeled S1 subsite specificity. The most dramatic change in specificity resulted from substitution with proline, which collapsed S1 subsite specificity such that only substrates with P1-Arg, -Lys, or -Met were appreciably hydrolyzed. The structure of PfA-M1 V459P revealed that the proline substitution induced a local conformational change in the polypeptide backbone that resulted in a narrowed S1 subsite. The restricted specificity and active site backbone conformation of PfA-M1 V459P mirrored those of endoplasmic reticulum aminopeptidase 2, a human enzyme with proline in the variable S1 subsite position. Our results provide compelling evidence that changes in the variable residue in the S1 subsite of M1-aminopeptidases have facilitated the evolution of new specificities and ultimately novel functions for this important class of enzymes. PMID:23897806

  16. Residuation theory

    CERN Document Server

    Blyth, T S; Sneddon, I N; Stark, M

    1972-01-01

    Residuation Theory aims to contribute to literature in the field of ordered algebraic structures, especially on the subject of residual mappings. The book is divided into three chapters. Chapter 1 focuses on ordered sets; directed sets; semilattices; lattices; and complete lattices. Chapter 2 tackles Baer rings; Baer semigroups; Foulis semigroups; residual mappings; the notion of involution; and Boolean algebras. Chapter 3 covers residuated groupoids and semigroups; group homomorphic and isotone homomorphic Boolean images of ordered semigroups; Dubreil-Jacotin and Brouwer semigroups; and loli

  17. Modulation of ligand–heme reactivity by binding pocket residues demonstrated in cytochrome c' over the femtosecond–second temporal range

    OpenAIRE

    Russell, Henry J.; Hardman, Samantha J. O.; Heyes, Derren J.; Hough, Michael A.; Greetham, Gregory M.; Towrie, Michael; Hay, Sam; Scrutton, Nigel S.

    2013-01-01

    The ability of hemoproteins to discriminate between diatomic molecules, and the subsequent affinity for their chosen ligand, is fundamental to the existence of life. These processes are often controlled by precise structural arrangements in proteins, with heme pocket residues driving reactivity and specificity. One such protein is cytochrome c', which has the ability to bind nitric oxide (NO) and carbon monoxide (CO) on opposite faces of the heme, a property that is shared with soluble guany...

  18. Residual stresses

    International Nuclear Information System (INIS)

    The principal effect of unloading a material strained into the plastic range is to create a permanent set (plastic deformation), which if restricted somehow, gives rise to a system of self-balancing within the same member or reaction balanced by other members of the structure., known as residual stresses. These stresses stay there as locked-in stresses, in the body or a part of it in the absence of any external loading. Residual stresses are induced during hot-rolling and welding differential cooling, cold-forming and extruding: cold straightening and spot heating, fabrication and forced fitting of components constraining the structure to a particular geometry. The areas which cool more quickly develop residual compressive stresses, while the slower cooling areas develop residual tensile stresses, and a self-balancing or reaction balanced system of residual stresses is formed. The phenomenon of residual stresses is the most challenging in its application in surface modification techniques determining endurance mechanism against fracture and fatigue failures. This paper discusses the mechanism of residual stresses, that how the residual stresses are fanned and what their behavior is under the action of external forces. Such as in the case of a circular bar under limit torque, rectangular beam under limt moment, reclaiming of shafts welds and peening etc. (author)

  19. Multiparticle superstring tree amplitudes

    International Nuclear Information System (INIS)

    Covariant functional integral methods are used to derive formulas for (type I, type II, and heterotic) superstring tree amplitudes having arbitrary numbers of external ground-state bosons, thereby obtaining superstring generalizations of the Koba-Nielsen formula. The disk and projective plane diagrams of the type I superstring are calculated, and the divergences are shown to cancel in the case of gauge group SO(32); the dilaton tadpole is shown to vanish for SO(32) when the contributions from the disk and projective plane are added. The gauge fixing of the odd elements of the invariance groups of the amplitudes is shown to play an essential role. (orig.)

  20. N=4 Scattering Amplitudes and the Deformed Graßmannian

    CERN Document Server

    Ferro, Livia; Staudacher, Matthias

    2014-01-01

    Some time ago the general tree-level scattering amplitudes of N=4 Super Yang-Mills theory were expressed as certain Grassmannian contour integrals. These remarkable formulas allow to clearly expose the super-conformal, dual super-conformal, and Yangian symmetries of the amplitudes. Using ideas from integrability it was recently shown that the building blocks of the amplitudes permit a natural multi-parameter deformation. However, this approach had been criticized by the observation that it seemed impossible to reassemble the building blocks into Yangian-invariant deformed non-MHV amplitudes. In this note we demonstrate that the deformations may be succinctly summarized by a simple modification of the measure of the Grassmannian integrals, leading to a Yangian-invariant deformation of the general tree-level amplitudes. Interestingly, the deformed building-blocks appear as residues of poles in the spectral parameter planes. Given that the contour integrals also contain information on the amplitudes at loop-leve...

  1. Amplitude function mismatch

    International Nuclear Information System (INIS)

    The authors develop the general equation of motion of an amplitude function mismatch in an accelerator lattice and look at its solution for some interesting cases. For a free ?-wave oscillation the amplitude of the mismatch is written in terms of the determinant of a single matrix made up of the difference between the new Courant-Snyder parameters and their ideal values. Using this result, once one calculates the mismatch of the amplitude function and its slope at one point in the lattice (at the end of a nearly matched insertion, for example), then the maximum mismatch downstream can be easily computed. The formalism is also used to describe emittance growth in a hadron synchrotron caused by amplitude function mismatches at injection. While most of the content of this paper is not new to the accelerator physics community, the authors thought it would be useful to place this important, basic information all in one place. Besides the classic work of Courant and Snyder, their sources include other papers, internal reports, and numerous discussions with colleagues

  2. A cascaded approach for correcting ionospheric contamination with large amplitude in HF skywave radars.

    Science.gov (United States)

    Li, Yajun; Wei, Yinsheng; Guo, Rujiang; Xu, Rongqing; Wang, Zhuoqun; Tang, Xiudong

    2014-01-01

    Ionospheric phase perturbation with large amplitude causes broadening sea clutter's Bragg peaks to overlap each other; the performance of traditional decontamination methods about filtering Bragg peak is poor, which greatly limits the detection performance of HF skywave radars. In view of the ionospheric phase perturbation with large amplitude, this paper proposes a cascaded approach based on improved S-method to correct the ionospheric phase contamination. This approach consists of two correction steps. At the first step, a time-frequency distribution method based on improved S-method is adopted and an optimal detection method is designed to obtain a coarse ionospheric modulation estimation from the time-frequency distribution. At the second correction step, based on the phase gradient algorithm (PGA) is exploited to eliminate the residual contamination. Finally, use the measured data to verify the effectiveness of the method. Simulation results show the time-frequency resolution of this method is high and is not affected by the interference of the cross term; ionospheric phase perturbation with large amplitude can be corrected in low signal-to-noise (SNR); such a cascade correction method has a good effect. PMID:24578656

  3. Quantitative Seismic Amplitude Analysis:

    OpenAIRE

    Dey, A. K.

    2011-01-01

    The Seismic Value Chain quantifies the cyclic interaction between seismic acquisition, imaging and reservoir characterization. Modern seismic innovation to address the global imbalance in hydrocarbon supply and demand requires such cyclic interaction of both feed-forward and feed-back processes. Currently, the seismic value chain paradigm is in a feed-forward mode. Modern seismic data now have the potential to yield the best images in terms of spatial resolution, amplitude accuracy, and incre...

  4. Monitoring a high--amplitude Delta Sct star for 152 days: discovery of 12 additional modes and modulation effects in the light curve of CoRoT 101155310

    CERN Document Server

    Poretti, Ennio; Weiss, Werner W; Bognar, Zsofia; Moya, Andy; Niemczura, Ewa; Suarez, Juan Carlos; Auvergne, Michel; Baglin, Annie; Baudin, Frederic; Benko, Jozsef M; Debosscher, Jonas; Garrido, Rafa; Mantegazza, Luciano; Paparo, Margit

    2011-01-01

    The detection of small-amplitude nonradial modes in high-amplitude Delta Sct (HADS) variables has been very elusive until at least five of them were detected in the light curve of V974 Oph obtained from ground-based observations. The combination of radial and nonradial modes has a high asteroseismic potential, thanks to the strong constraints we can put in the modelling. The continuous monitoring of ASAS 192647-0030.0=CoRoT 101155310 (P=0.1258 d, V=13.4) ensured from space by the CoRoT (Convection, Rotation and planetary Transits) mission constitutes a unique opportunity to exploit such potential. The 22270 CoRoT measurements were performed in the chromatic mode. They span 152 d and cover 1208 consecutive cycles. After the correction for one jump and the long-term drift, the level of the noise turned out to be 29 micromag. The phase shifts and amplitude ratios of the coloured CoRoT data, the HARPS spectra, and the period-luminosity relation were used to determine a self-consistent physical model. In turn, it ...

  5. Fusing gauge theory tree amplitudes into loop amplitudes

    International Nuclear Information System (INIS)

    We identify a large class of one-loop amplitudes for massless particles that can be constructed via unitarity from tree amplitudes, without any ambiguities. One-loop amplitudes for massless supersymmetric gauge theories fall into this class; in addition, many non-supersymmetric amplitudes can be rearranged to take advantage of the result. As applications, we construct the one-loop amplitudes for n-gluon scattering in N=1 supersymmetric theories with the helicity configuration of the Parke-Taylor tree amplitudes, and for six-gluon scattering in N=4 super-Yang-Mills theory for all helicity configurations. ((orig.))

  6. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire-KrF laser. Part 1. Regenerative amplification of subpicosecond pulses in a wide-aperture electron beam pumped KrF amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Zvorykin, V D; Ionin, Andrei A; Levchenko, A O; Mesyats, Gennadii A; Seleznev, L V; Sinitsyn, D V; Smetanin, Igor V; Sunchugasheva, E S; Ustinovskii, N N; Shutov, A V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2013-04-30

    Regenerative amplification of single and multiple ultrashort subpicosecond UV pulses in a wide-aperture KrF amplifier with an unstable confocal resonator was investigated on the GARPUN-MTW hybrid laser system. Amplitude-modulated 100-ns long UV radiation pulses with an energy of several tens of joules were obtained at the output of the system. The pulses were a combination of a quasi-stationary oscillation pulse and a train of amplified ultrashort pulses (USPs) with a peak power of 0.2-0.3 TW, which exceeded the power of free-running lasing pulse by three orders of magnitude. The population inversion recovery time in the active KrF laser medium was estimated: {tau}{sub c} {<=} 2.0 ns. Trains of USPs spaced at an interval {Delta}t Almost-Equal-To {tau}{sub c} were shown to exhibit the highest amplification efficiency. The production of amplitude-modulated UV pulses opens up the way to the production and maintenance of extended plasma channels in atmospheric air. (extreme light fields and their applications)

  7. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire—KrF laser. Part 1. Regenerative amplification of subpicosecond pulses in a wide-aperture electron beam pumped KrF amplifier

    International Nuclear Information System (INIS)

    Regenerative amplification of single and multiple ultrashort subpicosecond UV pulses in a wide-aperture KrF amplifier with an unstable confocal resonator was investigated on the GARPUN-MTW hybrid laser system. Amplitude-modulated 100-ns long UV radiation pulses with an energy of several tens of joules were obtained at the output of the system. The pulses were a combination of a quasi-stationary oscillation pulse and a train of amplified ultrashort pulses (USPs) with a peak power of 0.2–0.3 TW, which exceeded the power of free-running lasing pulse by three orders of magnitude. The population inversion recovery time in the active KrF laser medium was estimated: ?c ? 2.0 ns. Trains of USPs spaced at an interval ?t ? ?c were shown to exhibit the highest amplification efficiency. The production of amplitude-modulated UV pulses opens up the way to the production and maintenance of extended plasma channels in atmospheric air. (extreme light fields and their applications)

  8. Main results on the RF amplitude and phase regulation systems in operation at GANIL

    International Nuclear Information System (INIS)

    The general features of the amplitude and phase regulations and their control systems are briefly reviewed. These feedback control systems are fully under the control of the main computer aided by dedicated CAMAC microprocessors for actions such as starting, parameters tuning or phase stability surveying. Numerous results obtained with spectrum analysis method give the actual RF purity and the residual modulation and crossmodulation noise level for all RF signals picked up in the RF resonators. A typical value for the noise immunity is .80 dB below the carrier at 100 Hz deviation. Another set of results gives the actual long term phase drift between resonators (<0.2 RF degree within 6 hours). The stability of the RF phases is confirmed by on line beam phase measurements

  9. Modulation of the internal aldimine pK(a)'s of 1-aminocyclopropane-1-carboxylate synthase and aspartate aminotransferase by specific active site residues.

    Science.gov (United States)

    Eliot, Andrew C; Kirsch, Jack F

    2002-03-19

    The active sites of the homologous pyridoxal phosphate- (PLP-) dependent enzymes 1-aminocyclopropane-1-carboxylate (ACC) synthase and aspartate aminotransferase (AATase) are almost entirely conserved, yet the pK(a)'s of the two internal aldimines are 9.3 and 7.0, respectively, to complement the substrate pK(a)'s (S-adenosylmethionine pK(a) = 7.8 and aspartate pK(a) = 9.9). This complementation is required for maximum enzymatic activity in the physiological pH range. The most prominent structural difference in the active site is that Ile232 of ACC synthase is replaced by alanine in AATase. The I232A mutation was introduced into ACC synthase with a resulting 1.1 unit decrease (from 9.3 to 8.2) in the aldimine pK(a), thus identifying Ile232 as a major determinant of the high pK(a) of ACC synthase. The mutation also resulted in reduced k(cat) (0.5 vs 11 s(-1)) and k(cat)/K(m) values (5.0 x 10(4) vs 1.2 x 10(6) M(-1) s(-1)). The effect of the mutation is interpreted as the result of shortening of the Tyr233-PLP hydrogen bond. Addition of the Y233F mutation to the I232A ACC synthase to generate the double mutant I232A/Y233F raised the pK(a) from 8.2 to 8.8, because the Y233F mutation eliminates the hydrogen bond between that residue and PLP. The introduction of the retro mutation A224I into AATase raised the aldimine pK(a) of that enzyme from 6.96 to 7.16 and resulted in a decrease in single-turnover k(max) (108 vs 900 s(-1) for aspartate) and k(max)/K(m)(app) (7.5 x 10(4) vs 3.8 x 10(5) M(-1) s(-1)) values. The distance from the pyridine nitrogen of the cofactor to a conserved aspartate residue is 2.6 A in AATase and 3.8 A in ACC synthase. The D230E mutation introduced into ACC synthase to close this distance increases the aldimine pK(a) from 9.3 to 10.0, as would be predicted from a shortened hydrogen bond. PMID:11888303

  10. On triple-cut of scattering amplitudes

    International Nuclear Information System (INIS)

    It is analysed the triple-cut of one-loop amplitudes in dimensional regularisation within spinor-helicity representation. The triple-cut is defined as a difference of two double-cuts with the same particle contents, and a same propagator carrying, respectively, causal and anti-causal prescription in each of the two cuts. That turns out into an effective tool for extracting the coefficients of three-point functions (and higher-point ones) from one-loop amplitudes. The phase-space integration is oversimplified by using residues theorem to perform the integration on the spinor variables, via the holomorphic anomaly, and a trivial integration on the Feynman parameter. The results are valid for arbitrary values of dimensions

  11. Spinor Helicity Amplitudes Method

    Science.gov (United States)

    Niu, Li; Mao, Song; Gang, Li; Jian-You, Guo

    2015-02-01

    In this paper, we introduce the spinor helicity amplitude method. We provide the approaches to handle with massless fermions, massive spinors and polarization vectors respectively, then applied this method to some examples such as e + e -?? + ? -, e - ??e - ?, bar {q}q to gg processes. Among the examples, bar {q}qto gg process presented in the antecedent literatures, but we provide a more detailed calculation, and others are gave for the first time. We summarize all kinds of the situations, and give the needed formulas in appendix, which will be of use to collect these analysis formulas in one place.

  12. Scattering amplitudes at finite temperature

    International Nuclear Information System (INIS)

    We present a simple set of rules for obtaining the imaginary part of a self-energy diagram at finite temperature as a product of tree amplitudes. These diagrams correspond to physical scattering amplitudes

  13. Dosimetric effect of intrafraction motion and residual setup error for hypofractionated prostate intensity-modulated radiotherapy with online cone beam computed tomography image guidance.

    LENUS (Irish Health Repository)

    Adamson, Justus

    2012-02-01

    PURPOSE: To quantify the dosimetric effect and margins required to account for prostate intrafractional translation and residual setup error in a cone beam computed tomography (CBCT)-guided hypofractionated radiotherapy protocol. METHODS AND MATERIALS: Prostate position after online correction was measured during dose delivery using simultaneous kV fluoroscopy and posttreatment CBCT in 572 fractions to 30 patients. We reconstructed the dose distribution to the clinical tumor volume (CTV) using a convolution of the static dose with a probability density function (PDF) based on the kV fluoroscopy, and we calculated the minimum dose received by 99% of the CTV (D(99)). We compared reconstructed doses when the convolution was performed per beam, per patient, and when the PDF was created using posttreatment CBCT. We determined the minimum axis-specific margins to limit CTV D(99) reduction to 1%. RESULTS: For 3-mm margins, D(99) reduction was <\\/=5% for 29\\/30 patients. Using post-CBCT rather than localizations at treatment delivery exaggerated dosimetric effects by ~47%, while there was no such bias between the dose convolved with a beam-specific and patient-specific PDF. After eight fractions, final cumulative D(99) could be predicted with a root mean square error of <1%. For 90% of patients, the required margins were <\\/=2, 4, and 3 mm, with 70%, 40%, and 33% of patients requiring no right-left (RL), anteroposterior (AP), and superoinferior margins, respectively. CONCLUSIONS: For protocols with CBCT guidance, RL, AP, and SI margins of 2, 4, and 3 mm are sufficient to account for translational errors; however, the large variation in patient-specific margins suggests that adaptive management may be beneficial.

  14. Dosimetric Effect of Intrafraction Motion and Residual Setup Error for Hypofractionated Prostate Intensity-Modulated Radiotherapy With Online Cone Beam Computed Tomography Image Guidance

    International Nuclear Information System (INIS)

    Purpose: To quantify the dosimetric effect and margins required to account for prostate intrafractional translation and residual setup error in a cone beam computed tomography (CBCT)-guided hypofractionated radiotherapy protocol. Methods and Materials: Prostate position after online correction was measured during dose delivery using simultaneous kV fluoroscopy and posttreatment CBCT in 572 fractions to 30 patients. We reconstructed the dose distribution to the clinical tumor volume (CTV) using a convolution of the static dose with a probability density function (PDF) based on the kV fluoroscopy, and we calculated the minimum dose received by 99% of the CTV (D99). We compared reconstructed doses when the convolution was performed per beam, per patient, and when the PDF was created using posttreatment CBCT. We determined the minimum axis-specific margins to limit CTV D99 reduction to 1%. Results: For 3-mm margins, D99 reduction was ?5% for 29/30 patients. Using post-CBCT rather than localizations at treatment delivery exaggerated dosimetric effects by ?47%, while there was no such bias between the dose convolved with a beam-specific and patient-specific PDF. After eight fractions, final cumulative D99 could be predicted with a root mean square error of <1%. For 90% of patients, the required margins were ?2, 4, and 3 mm, with 70%, 40%, and 33% of patients requiring no right-left (RL), anteroposterior (AP), and superoinfernteroposterior (AP), and superoinferior margins, respectively. Conclusions: For protocols with CBCT guidance, RL, AP, and SI margins of 2, 4, and 3 mm are sufficient to account for translational errors; however, the large variation in patient-specific margins suggests that adaptive management may be beneficial.

  15. Statistical amplitude scale estimation for quantization-based watermarking:

    OpenAIRE

    Shterev, I. D.; Lagendijk, I. L.; Heusdens, R.

    2004-01-01

    Quantization-based watermarking schemes are vulnerable to amplitude scaling. Therefore the scaling factor has to be accounted for either at the encoder, or at the decoder, prior to watermark decoding. In this paper we derive the marginal probability density model for the watermarked and attacked data, when the attack channel consists of amplitude scaling followed by additive noise. The encoder is Quantization Index Modulation with Distortion Compensation. Based on this model we obtain two est...

  16. Closed string amplitudes as single-valued open string amplitudes

    International Nuclear Information System (INIS)

    We show that the single trace heterotic N-point tree-level gauge amplitude ANHET can be obtained from the corresponding type I amplitude ANI by the single-valued (sv) projection: ANHET=sv(ANI). This projection maps multiple zeta values to single-valued multiple zeta values. The latter represent a subclass of multiple zeta values originating from single-valued multiple polylogarithms at unity. Similar relations between open and closed string amplitudes or amplitudes of different string vacua can be established. As a consequence the ??-expansion of a closed string amplitude is dictated by that of the corresponding open string amplitude. The combination of single-valued projections, Kawai–Lewellen–Tye relations and Mellin correspondence reveal a unity of all tree-level open and closed superstring amplitudes together with the maximally supersymmetric Yang–Mills and supergravity theories

  17. Closed String Amplitudes as Single-Valued Open String Amplitudes

    CERN Document Server

    Stieberger, Stephan

    2014-01-01

    We show that the single trace heterotic N-point tree-level gauge amplitude A_HET can be obtained from the corresponding type I amplitude A_I by the single-valued (sv) projection: A_HET=sv(A_I). This projection maps multiple zeta values to single-valued multiple zeta values. The latter represent a subclass of multiple zeta values originating from single-valued multiple polylogarithms at unity. Similar relations between open and closed string amplitudes or amplitudes of different string vacua can be established. As a consequence the alpha'-expansion of a closed string amplitude is dictated by that of the corresponding open string amplitude. The combination of single-valued projections, Kawai-Lewellen-Tye relations and Mellin correspondence reveal a unity of all tree-level open and closed superstring amplitudes together with the maximally supersymmetric Yang-Mills and supergravity theories.

  18. Amplitude equations for stochastic partial differential equations

    CERN Document Server

    Blömker, Dirk

    2007-01-01

    Rigorous error estimates for amplitude equations are well known for deterministic PDEs, and there is a large body of literature over the past two decades. However, there seems to be a lack of literature for stochastic equations, although the theory is being successfully used in the applied community, such as for convective instabilities, without reliable error estimates at hand. This book is the first step in closing this gap. The author provides details about the reduction of dynamics to more simpler equations via amplitude or modulation equations, which relies on the natural separation of time-scales present near a change of stability. For students, the book provides a lucid introduction to the subject highlighting the new tools necessary for stochastic equations, while serving as an excellent guide to recent research.

  19. Direct modulation of 56 Gbps duobinary-4-PAM

    DEFF Research Database (Denmark)

    Suhr, Lau Frejstrup; Vegas Olmos, Juan José

    This paper reports on the direct modulation of externally modulated laser and transmission through single mode fiber of a 56 Gbps duobinary-4-pulse amplitude modulation signal through 10 GHz class optics.

  20. High Frequency Amplitude Detector for GMI Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Aktham Asfour

    2014-12-01

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

  1. Fringe free holographic measurements of large amplitude vibrations

    CERN Document Server

    Joud, Fadwa; Laloë, Franck; Michael, Atlan; Hare, Jean; Gross, Michel

    2010-01-01

    In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; due to the limited resolution of images, measurements of large amplitudes are not accessible. We demonstrate a technique that suppresses the necessity of fringe counting: frequency sideband imaging, where the order of the sideband is considered as a marker of the amplitude. The measurement is completely local: no comparison with another reference point on the object is necessary. It involves a sharp variation of a signal, which makes it robust against perturbations. The method is demonstrated in an experiment made with a vibrating clarinet reed; phase modulations as large as 1000 radians have been measured.

  2. Residual basins

    International Nuclear Information System (INIS)

    Exploration for uranium carried out over a major portion of the Rio Grande do Sul Shield has revealed a number of small residual basins developed along glacially eroded channels of pre-Permian age. Mineralization of uranium occurs in two distinct sedimentary units. The lower unit consists of rhythmites overlain by a sequence of black shales, siltstones and coal seams, while the upper one is dominated by sandstones of probable fluvial origin. (Author)

  3. Linearized rays, amplitude and inversion

    Science.gov (United States)

    Nowack, Robert L.; Lutter, William J.

    1988-03-01

    In this paper, ray theoretical amplitudes and travel times are calculated in slightly perturbed velocity models using perturbation analysis. Also, test inversions using travel time and amplitude are computed. The pertubation method is tested using a 3-D velocity model for NORSAR having velocity variations up to 8.0 percent. The perturbed amplitudes are found to be in excellent agreement with the calculated ray amplitudes. Velocity inversions based on travel time and amplitude are next investigated. Perturbation analysis using linearized ray equations is efficiently used to compute amplitude derivatives with respect to model parameters. The trial linearized inversions use smaller velocity variations of 1.7 percent to avoid possible effects due to ray shift, even though the perturbation analysis is valid for larger variations. The trial 2-D inversion results show that linearized amplitude inversions are complementary and not redundant to travel time inversions, even in smoothly varying models.

  4. Existence and propagation of finite amplitude upper hybrid solitary waves

    International Nuclear Information System (INIS)

    Known results on the coupling of upper hybrid waves with linear low-frequency background modulations are generalized to include finite amplitude density and magnetic field modulations. The present results are thus valid beyond the usual cubic nonlinear Schroedinger equation description. Conditions for the existence of envelope solitons are derived. Super- and sub-Alfvenic upper hybrid solitons with their associated density depressions or humps can appear. Special cases are discussed. (author)

  5. Dual-beam wavelength modulation spectroscopy for sensitive detection of water vapor

    Science.gov (United States)

    Wang, Qiang; Chang, Jun; Wei, Wei; Zhu, Cunguang; Tian, Changbin

    2014-12-01

    A technique was reported for sensitive detection of water vapor based on dual-beam wavelength modulation spectroscopy (WMS). Particular attention was focused on the problem of laser power variation (LPV) and residual amplitude modulation (RAM), which accounted for the absorption profile's distortion during application of WMS. Impact from LPV and RAM was eliminated by photocurrent normalization through a balanced ratiometric detector, which was a dual-beam technique with shot noise-level performance. When consideration of distortion was required, this could enormously simplify the spectra analysis procedure. In the experiment symmetry of the WMS, profile had gotten an improvement by a factor of about 102 compared with traditional single-beam method. During the application test of water vapor detection, the detected amplitude of WMS was well proportional to water vapor concentration ranging from 25 to 1,048 ppmv and the sensitivity was achieved to be 52 ppbv for just a 10-cm optical path length.

  6. Encouraging Early Clinical Outcomes With Helical Tomotherapy–Based Image-Guided Intensity-Modulated Radiation Therapy for Residual, Recurrent, and/or Progressive Benign/Low-Grade Intracranial Tumors: A Comprehensive Evaluation

    International Nuclear Information System (INIS)

    Purpose: To report early clinical outcomes of helical tomotherapy (HT)-based image-guided intensity-modulated radiation therapy (IMRT) in brain tumors of varying shape, size, and location. Materials and Methods: Patients with residual, recurrent, and/or progressive low-grade intracranial and skull-base tumors were treated on a prospective protocol of HT-based IMRT and followed clinicoradiologically. Standardized metrics were used for plan evaluation and outcome analysis. Results: Twenty-seven patients with 30 lesions were treated to a median radiotherapy dose of 54 Gy in 30 fractions. All HT plans resulted in excellent target volume coverage with steep dose-gradients. The mean (standard deviation) dose homogeneity index and conformity index was 0.07 (0.05) and 0.71 (0.08) respectively. At first response assessment, 20 of 30 lesions were stable, whereas 9 showed partial regression. One patient with a recurrent clival chordoma though neurologically stable showed imaging-defined progression, whereas another patient with stable disease on serial imaging had sustained neurologic worsening. With a median follow-up of 19 months (interquartile range, 11–26 months), the 2-year clinicoradiological progression-free survival and overall survival was 93.3% and 100% respectively. Conclusions: Careful selection of radiotherapy technique is warranted for benign/low-grade brain tumors to achieve durable local control with minimum long-term morbidity. Large or complex-shaped tumors bbidity. Large or complex-shaped tumors benefit most from IMRT. Our early clinical experience of HT-based IMRT for brain tumors has been encouraging.

  7. Multilevel Modulation formats for Optical Communication

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee

    2008-01-01

    This thesis studies the use of multilevel modulation formats for optical communication systems. Multilevel modulation is an attractive method of increasing the spectral efficiency of optical communication systems. Various modulation formats employing phase modulation, amplitude modulation or a combination of the two have been studied. The use of polarization multiplexing (PolMux) to double the bit rate has also been investigated. The impact of transmission impairments such as chromatic dispersion, self phase modulation and cross phase modulation has been investigated. The feasibility of multilevel modulation for network oriented scenarios has been demonstrated.

  8. Positive Amplitudes In The Amplituhedron

    CERN Document Server

    Arkani-Hamed, Nima; Trnka, Jaroslav

    2014-01-01

    The all-loop integrand for scattering amplitudes in planar N = 4 SYM is determined by an "amplitude form" with logarithmic singularities on the boundary of the amplituhedron. In this note we provide strong evidence for a new striking property of the superamplitude, which we conjecture to be true to all loop orders: the amplitude form is positive when evaluated inside the amplituhedron. The statement is sensibly formulated thanks to the natural "bosonization" of the superamplitude associated with the amplituhedron geometry. However this positivity is not manifest in any of the current approaches to scattering amplitudes, and in particular not in the cellulations of the amplituhedron related to on-shell diagrams and the positive grassmannian. The surprising positivity of the form suggests the existence of a "dual amplituhedron" formulation where this feature would be made obvious. We also suggest that the positivity is associated with an extended picture of amplituhedron geometry, with the amplituhedron sitting...

  9. Amplitude-mediated chimera states

    Science.gov (United States)

    Sethia, Gautam C.; Sen, Abhijit; Johnston, George L.

    2013-10-01

    We investigate the possibility of obtaining chimera state solutions of the nonlocal complex Ginzburg-Landau equation (NLCGLE) in the strong coupling limit when it is important to retain amplitude variations. Our numerical studies reveal the existence of a variety of amplitude-mediated chimera states (including stationary and nonstationary two-cluster chimera states) that display intermittent emergence and decay of amplitude dips in their phase incoherent regions. The existence regions of the single-cluster chimera state and both types of two-cluster chimera states are mapped numerically in the parameter space of C1 and C2, the linear and nonlinear dispersion coefficients, respectively, of the NLCGLE. They represent a new domain of dynamical behavior in the well-explored rich phase diagram of this system. The amplitude-mediated chimera states may find useful applications in understanding spatiotemporal patterns found in fluid flow experiments and other strongly coupled systems.

  10. Scattering amplitudes in gauge theories

    CERN Document Server

    Henn, Johannes M

    2014-01-01

    At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge.   These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum ...

  11. Amplitude death state for hearing

    CERN Document Server

    Ahn, Kang-Hun

    2012-01-01

    We propose amplitude death phenomenon as an underlying mechanism of auditory transduction. When non-identical auditory hair bundles are elastically coupled, their spontaneous oscillations can be quenched to form an amplitude death state. We show, in this state, the hair cells are quiet and ready to detect oscillatory stimulus with coupling-strength dependent amplification. Numerical demonstration of the mechanism suggests that the non-uniformity of coupled hair cells can contribute to noise-robust auditory transduction.

  12. Large amplitude electron plasma oscillations

    International Nuclear Information System (INIS)

    We consider a cold plasma in order to find new large-amplitude wave solutions in the long-wavelength limit. Accordingly we derive two generic coupled equations which describe the energy exchange between the electrostatic and electromagnetic waves. A new kind of quasi-periodic behavior is found. Our derivations may be considered as a prerequisite to extended studies of stimulated Raman scattering for cases where the wave amplitudes are so large that standard perturbation techniques are not applicable.

  13. Infrared singularities in QCD amplitudes

    OpenAIRE

    Magnea, Lorenzo

    2009-01-01

    We review recent progress in determining the infrared singularity structure of on-shell scattering amplitudes in massless gauge theories. We present a simple ansatz where soft singularities of any scattering amplitude of massless partons, to any loop order, are written as a sum over colour dipoles, governed by the cusp anomalous dimension. We explain how this formula was obtained, as the simplest solution to a newly-derived set of equations constraining the singularity struc...

  14. Motivic Amplitudes and Cluster Coordinates

    CERN Document Server

    Golden, John; Spradlin, Marcus; Vergu, Cristian; Volovich, Anastasia

    2014-01-01

    In this paper we study motivic amplitudes--objects which contain all of the essential mathematical content of scattering amplitudes in planar SYM theory in a completely canonical way, free from the ambiguities inherent in any attempt to choose particular functional representatives. We find that the cluster structure on the kinematic configuration space Conf_n(P^3) underlies the structure of motivic amplitudes. Specifically, we compute explicitly the coproduct of the two-loop seven-particle MHV motivic amplitude A_{7,2} and find that like the previously known six-particle amplitude, it depends only on certain preferred coordinates known in the mathematics literature as cluster X-coordinates on Conf_n(P^3). We also find intriguing relations between motivic amplitudes and the geometry of generalized associahedrons, to which cluster coordinates have a natural combinatoric connection. For example, the obstruction to A_{7,2} being expressible in terms of classical polylogarithms is most naturally represented by cer...

  15. Observation of Modulation Transfer Spectroscopy in the Deep Modulation Regime

    International Nuclear Information System (INIS)

    We observe the modulation transfer spectroscopy on the D2 line of 87Rb in a rubidium cell with acoustic-optic modulator in the deep modulation regime. In this regime, the sidebands of the pump beam are involved in the four-wave mixing processes, which increase the signal gradients and the peak-to-peak amplitudes of both the absorption and dispersion components. (fundamental areas of phenomenology(including applications))

  16. Observation of Modulation Transfer Spectroscopy in the Deep Modulation Regime

    Science.gov (United States)

    Zhou, Zi-Chao; Wei, Rong; Shi, Chun-Yan; Wang, Yu-Zhu

    2010-12-01

    We observe the modulation transfer spectroscopy on the D2 line of 87Rb in a rubidium cell with acoustic-optic modulator in the deep modulation regime. In this regime, the sidebands of the pump beam are involved in the four-wave mixing processes, which increase the signal gradients and the peak-to-peak amplitudes of both the absorption and dispersion components.

  17. Variable amplitude fatigue crack growth behavior - a short overview

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Konjengbam Darunkumar [Indian Institute of Technology, Guwahati (India); Parry, Matthew Roger [Airbus Operations Ltd, Bristol (United Kingdom); Sinclair, Ian [University of Southampton, Southampton (United Kingdom)

    2011-03-15

    A short overview concerning variable amplitude (VA) fatigue crack growth behavior is presented in this paper. The topics covered in this review encompass important issues pertaining to both single and repeated overload transients. Reviews on transient post overload effects such as plasticity induced crack closure, crack tip blunting, residual stresses, crack deflection and branching, activation of near threshold mechanisms, strain hardening are highlighted. A brief summary on experimental trends and finite element modelling of overload induced crack closure is also presented.

  18. Recognition of OFDM Modulation Method

    Directory of Open Access Journals (Sweden)

    K. Ulovec

    2008-04-01

    Full Text Available This contribution deals with asynchronous noncoherent recognition of modulation types. The main aim is to recognize OFDM modulation method from some other single-carrier analog and digital modulation types in the presence of AWGN noise. The described solution of recognizer uses key features of the received signal. The signal amplitude is observed at the output of the quadrature intermediate-frequency stage. The properties of the recognizer are verified by simulations using Matlab.

  19. Generator coordinate amplitude for scattering

    International Nuclear Information System (INIS)

    In the generator coordinate method for scattering the proper boundary conditions is accomplished by requiring the GC amplitude to satisfy an integral equation of the first kind. Attempts to solve this problem are first reviewed and then an improved approximation is proposed which is applicable to a wider class of scattering problems in addition to the Coulomb scattering. A better approximation is obtained in the asymptotic region, where the generator coordinate, i.e., the distance between two shell-model wells of the fragments, is larger than the touching distance of the colliding nuclei, by deriving partial differential equations of first order for the terms of an asymptotic series in 1/E, where E is the scattering energy. Extracting the information on the GC amplitude for small values of the generator parameter from the integral equation of the first kind is an ill-posed problem. It is shown that the method of statistical regularization offers a powerful and controllable procedure to uncover the GC amplitude. The unknown GC amplitude is treated as a random function with an a priori distribution of probability which is based on the assumption that the amplitude is bounded and that the errors in the input are random with zero expectation value. A useful procedure is found for fixing parameters of the a priori distribution. The solution for small values of the GC parameter is expressed in the form of a Dini series. The method is applied to the calculation of the GC amps applied to the calculation of the GC amplitude for scattering of two ?-particles at 15 MeV c.m. energy. The measure of the accuracy is the difference between the input wave function of relative motion and the result of folding of the GC amplitude with the kernel of the integral equation. The prescribed accuracy is reached with this method on a much larger interval than with any previously proposed method. (orig.)

  20. Practical analyticity of scattering amplitudes

    International Nuclear Information System (INIS)

    It is well known that a significant proportion of the rigorous results obtained in the framework of axiomatic quantum field theory is based on the use of the analytic properties of the scattering amplitude in the complex plane of the energy variable E. However, it is only for a restricted class of scattering processes and only for a restricted range of values of the square of the momentum transfer that one can prove analyticity of the amplitude in the entire complex E plane, except for cuts along the real axis. For other processes, which include, in particular, the practically very important process of nucleon-nucleon scattering, analyticity of the scattering amplitude in such a maximally large region cannot be proved for any values of the momentum transfer. In the general case of an arbitrary two-particle scattering process involving particles of nonzero mass only the following properties of analyticity of the amplitude with respect to the energy for fixed physical value of t have been proved: (a) the amplitude is analytic in the complete complex E plane except for the physical cuts and a certain region D in the neighborhood of the origin. The actual form of D is unknown - it is known only that it has a finite size (but, in general, this may be very large and increase with increasing t as |t|3); (b) the amplitude is analytic in some neighborhood (in general, arbitrarily small) of each physical point. It is shown that for an arbitrary two-particle scatterinat for an arbitrary two-particle scattering process one can, for any physical value of the momentum transfer, construct a function that is analytic in a maximally large region and simultaneously approximates with arbitrary good accuracy the scattering amplitude for physical values of the energy

  1. The face amplitude of spinfoam quantum gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, Eugenio; Regoli, Daniele; Rovelli, Carlo, E-mail: rovelli@cpt.univ-mrs.f [Centre de Physique Theorique de Luminy, Case 907, F-13288 Marseille (France)

    2010-09-21

    The structure of the boundary Hilbert space and the condition that amplitudes behave appropriately under compositions determine the face amplitude of a spinfoam theory. In quantum gravity the face amplitude turns out to be simpler than originally thought.

  2. The face amplitude of spinfoam quantum gravity

    OpenAIRE

    Bianchi, Eugenio; Regoli, Daniele; Rovelli, Carlo

    2010-01-01

    Abstract The structure of the boundary Hilbert-space and the condition that amplitudes behave appropriately under compositions determine the face amplitude of a spinfoam theory. In quantum gravity the face amplitude turns out to be simpler than originally thought.

  3. Face amplitude of spinfoam quantum gravity

    CERN Document Server

    Bianchi, Eugenio; Rovelli, Carlo

    2010-01-01

    The structure of the boundary Hilbert-space and the condition that amplitudes behave appropriately under compositions determine the face amplitude of a spinfoam theory. In quantum gravity the face amplitude turns out to be simpler than originally thought.

  4. Large amplitude oscillatory elongation flow

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Laillé, Philippe

    2008-01-01

    A filament stretching rheometer (FSR) was used for measuring the elongation flow with a large amplitude oscillative elongation imposed upon the flow. The large amplitude oscillation imposed upon the elongational flow as a function of the time t was defined as epsilon(t) =(epsilon) over dot(0)t + Lambda[1 - cos( 2 pi Omega(epsilon) over dot(0)t)] where epsilon is the Hencky strain, (epsilon) over dot(0) is a constant elongational rate for the base elongational flow, Lambda the strain amplitude ( Lambda >= 0), and Omega the strain frequency. A narrow molecular mass distribution linear polystyrene with a molecular weight of 145 kg/ mol was subjected to the oscillative flow. The onset of the steady periodic regime is reached at the same Hencky strain as the onset of the steady elongational viscosity ( Lambda = 0). The integral molecular stress function formulation within the 'interchain pressure' concept agrees qualitatively with the experiments.

  5. Topological amplitudes in string theory

    International Nuclear Information System (INIS)

    We show that certain type II string amplitudes at genus g are given by the topological partition Fg discussed recently by Bershadsky, Cecotti, Ooguri and Vafa. These amplitudes give rise to a term in the four-dimensional effective action of the form ?gFgW2g, where W is the chiral superfield of N = 2 supergravitational multiplet. The holomorphic anomaly of Fg is related to non-localities of the effective action due to the propagation of massless states. This result generalizes the holomorphic anomaly of the one loop case which is known to lead to non-harmonic gravitational couplings. (author). 22 refs, 2 figs

  6. Amplitude and phase modulation accompanying laser beam trapping in plasmas

    International Nuclear Information System (INIS)

    The self-trapping of laser beams in underdense plasmas or the propagation of laser beams in preformed favorable electron density distributions can be accompanied by gross distortions of pulse shape and spectrum. A simple theory is used to estimate the magnitude of these effects

  7. Thin Photoresponding Elements with Frequency and Amplitude Modulations.

    Czech Academy of Sciences Publication Activity Database

    Kluso?, Petr; Morozová, Magdalena; Dzik, P.; Veselý, M.

    Praha : ?eská spole?nost chemického inženýrství, 2013, s. 83. ISBN 978-80-02-02500-9. [Konference chemického a procesního inženýrství CHISA 2013 /60./. Srní, Šumava (CZ), 14.10.2013-17.10.2013] Institutional support: RVO:67985858 Keywords : metal oxide * electrochemical properties * photoelectrocatalytic activity Subject RIV: CI - Industrial Chemistry, Chemical Engineering www.chisa.cz/2013

  8. Intermittency in amplitude modulated dynamic atomic force microscopy

    International Nuclear Information System (INIS)

    From a mathematical point of view, the atomic force microscope (AFM) belongs to a special class of continuous time dynamical systems with intermittent impact collisions. Discontinuities of the velocity result from the collisions of the tip with the surface. Transition to chaos in non-linear systems can occur via the following four routes: bifurcation cascade, crisis, quasi-periodicity, and intermittency. For the AFM period doubling and period-adding cascades are well established. Other routes into chaos, however, also may play an important role. Time series data of a dynamic AFM experiment indicates a chaotic mode that is related to the intermittency route into chaos. The observed intermittency is characterized as a type III intermittency. Understanding the dynamics of the system will help improve the overall system performance by keeping the operation parameters of dynamic AFM in a range, where chaos can be avoided or at least controlled.

  9. AMPLITUDE AND PHASE MODULATION FOR ULTRASONIC WIRELESS COMMUNICATION

    OpenAIRE

    Nan Gao; Shigeru Shimamoto

    2014-01-01

    Short range wireless communications have been used more and more frequently in our life. But the electromagnetic fields waves also have some disadvantages. One of these disadvantages is health problems. Many studies shows the electromagnetic field waves using for communication may damage our health. And in most hospitals, they also have bans on the use of mobile phones and wide area networks because of Electromagnetic Interference. So this paper studied the use of ultrasound f...

  10. Wave instability under short-wave amplitude modulations

    International Nuclear Information System (INIS)

    The instabilities of nonlinear waves with a square-root dispersion ???(|k|) are studied. We present a new type of instability that affects wavelengths of the order of the carrier wave. This instability can initiate the formation of collapses and of narrow pulses.

  11. Various dielectrics used in DBD plasma discharge with amplitude modulation.

    Czech Academy of Sciences Publication Activity Database

    Uruba, Václav; Procházka, Pavel P.; Mat?jka, Milan

    -, ?. 6 (2009), s. 227-228. ISSN 1335-2938. [Stretnutie katedier mechaniky tekutín a termomechaniky. Jasná, Demanovská dolina, 24.06.2009-26.06.2009] R&D Projects: GA ?R GA101/08/1112 Institutional research plan: CEZ:AV0Z20760514 Keywords : plasma discharge * flow control * dielectric Subject RIV: BK - Fluid Dynamics

  12. Servo Control of High Degree of Linear Polarization Output from Polarization-Maintaining Fiber and its Application in Fiber-Component Based Frequency Modulation Spectroscopy

    Science.gov (United States)

    Ma, Weiguang; Li, Zhixin; Tan, Wei; Zhao, Gang; Fu, Xiaofang; Zhang, Lei; Dong, Lei; Yin, Wangbao; Jia, Suotang

    2013-11-01

    A novel servo control method has been developed to output a highly linear state of polarization (SOP) from a polarization-maintaining (PM) fiber. The correction signal is obtained using an SOP detection setup invented by Hänsch and Couillaud. This servo control method was then applied to fiber-component based frequency modulation spectroscopy experimentally to reduce the residual amplitude modulation (RAM) induced by nonlinear SOP incident to an electro-optic modulator. With active servo control, stable linear SOP output of PM fiber and pure frequency modulation lineshapes are obtained. Finally, long-term measurements of the dispersion background signal with feedback loop on and off are performed to evaluate the stability of RAM reduction.

  13. Large amplitude drop shape oscillations

    Science.gov (United States)

    Trinh, E. H.; Wang, T. G.

    1982-01-01

    An experimental study of large amplitude drop shape oscillation was conducted in immiscible liquids systems and with levitated free liquid drops in air. In liquid-liquid systems the results indicate the existence of familiar characteristics of nonlinear phenomena. The resonance frequency of the fundamental quadrupole mode of stationary, low viscosity Silicone oil drops acoustically levitated in water falls to noticeably low values as the amplitude of oscillation is increased. A typical, experimentally determined relative frequency decrease of a 0.5 cubic centimeters drop would be about 10% when the maximum deformed shape is characterized by a major to minor axial ratio of 1.9. On the other hand, no change in the fundamental mode frequency could be detected for 1 mm drops levitated in air. The experimental data for the decay constant of the quadrupole mode of drops immersed in a liquid host indicate a slight increase for larger oscillation amplitudes. A qualitative investigation of the internal fluid flows for such drops revealed the existence of steady internal circulation within drops oscillating in the fundamental and higher modes. The flow field configuration in the outer host liquid is also significantly altered when the drop oscillation amplitude becomes large.

  14. N-loop string amplitude

    International Nuclear Information System (INIS)

    Work on the derivation of an explicit perturbation series for string and superstring amplitudes is reviewed. The light-cone approach is emphasized, but some work on the Polyakov approach is also mentioned, and the two methods are compared. The calculation of the measure factor is outlined in the interacting-string picture

  15. N-loop string amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Mandelstam, S.

    1986-06-01

    Work on the derivation of an explicit perturbation series for string and superstring amplitudes is reviewed. The light-cone approach is emphasized, but some work on the Polyakov approach is also mentioned, and the two methods are compared. The calculation of the measure factor is outlined in the interacting-string picture. (LEW)

  16. Scattering amplitudes in gauge theories

    International Nuclear Information System (INIS)

    First monographical text on this fundamental topic. Course-tested, pedagogical and self-contained exposition. Includes exercises and solutions. At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge. These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum field theory. Bridging the gap between introductory courses on quantum field theory and state-of-the-art research, these concise yet self-contained and course-tested lecture notes are well-suited for a one-semester graduate level course or as a self-study guide for anyone interested in fundamental aspects of quantum field theory and its applications. The numerous exercises and solutions included will help readers to embrace and apply the material presented in the main text.

  17. Scattering amplitudes in gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Henn, Johannes M. [Institute for Advanced Study, Princeton, NJ (United States). School of Natural Sciences; Plefka, Jan C. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik

    2014-03-01

    First monographical text on this fundamental topic. Course-tested, pedagogical and self-contained exposition. Includes exercises and solutions. At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge. These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum field theory. Bridging the gap between introductory courses on quantum field theory and state-of-the-art research, these concise yet self-contained and course-tested lecture notes are well-suited for a one-semester graduate level course or as a self-study guide for anyone interested in fundamental aspects of quantum field theory and its applications. The numerous exercises and solutions included will help readers to embrace and apply the material presented in the main text.

  18. Seismic amplitude processing and inversion

    Science.gov (United States)

    Dev, Ashwani

    2008-10-01

    Hydrocarbon exploration requires reliable seismic amplitudes to identify oil and gas reservoirs. Erroneous seismic amplitude processing can potentially generate large economic losses. Correct seismic amplitude processing is pre-requisite for any amplitude dependent analysis. The accuracy of the subsurface image and estimation of the elastic properties of subsurface sediments depends upon the reliability of the amplitudes. Geophone groups are wavenumber filters that change the seismic amplitudes because of a wavenumber dependent information loss. Numerically defined filters deconvolve the recording group response from horizontal and the vertical component seismic data recorded with groups of uniform and non-uniform geophone sensitivity, different group lengths and spacing, and noise. The filtering effect of an array increases as the group length increases, and only the wavenumber range defined by the group interval can be correctly compensated for the group effect. A rigorous, explicit spatial antialias filter is designed and applied by removing the energy above the first Nyquist wavenumber in the horizontal slowness-frequency domain. The filter removes the spatially aliased frequencies selectively at each slowness. The aliased energy is dispersive and present at both small and large horizontal slownesses. The filter can be explicitly applied to regularly spaced or irregularly spaced traces and is independent of any event linearity assumption. An integrative interpretation approach defines the effect of the structural setting on gas hydrate and free-gas accumulation at a site at the East Casey fault zone in the Gulf of Mexico. At a well location, hydrates are interpreted as fracture fillings with maximum saturation ˜30% of the available pore space. Two low acoustic impedance (Ip) free-gas features terminating at the bottom simulating reflector (BSR) are interpreted from the 3D seismic data and the derived Ip volumes. The 2D Ip profile shows a contrast in BSR strength across the fault with limited lateral extent, and low-impedance freegas features along the fault suggest that fault is an active conduit for gas transport. Well logs, and the 2D and 3D Ip data suggest that the most readily available pore spaces determine the host formations for hydrate deposition, and that the distribution of hydrate and free-gas distributions depend largely on the faults within the localized depositional setting.

  19. Periodic instantons and scattering amplitudes

    International Nuclear Information System (INIS)

    We discuss the role of periodic euclidean solutions with two turning points and zero winding number (periodic instantons) in instanton induced processes below the sphaleron energy Esph. We find that the periodic instantons describe certain multiparticle scattering events leading to the transitions between topologically distinct vacua. Both the semiclassical amplitudes and inital and final states of these transitions are determined by the periodic instantons. Furthermore, the corresponding probabilities are maximal among all states of given energy. We show that at E ? Esph, the periodic instantons can be approximated by infinite chains of ordinary instantons and anti-instantons, and they naturally emerge as deformations of the zero energy instanton. In the framework of 2d abelian Higgs model and 4d electroweak theory we show, however, that there is not obvious relation between periodic instantons and two-particle scattering amplitudes. (orig.)

  20. SCRUNCHER phase and amplitude control

    International Nuclear Information System (INIS)

    The analog controller for phase and amplitude control of a 402.5 MHz super conducting cavity is described in this paper. The cavity is a single cell with niobium explosively bonded to a copper cavity. It is used as an energy compressor for pions at the Clinton P. Anderson Meson Physics Facility (LAMPF). The controller maintains cavity frequency to within 4 degrees in phase of the LAMPF beam frequency. Field amplitude is maintained to within 2 percent. This control is accomplished at critical coupling (Q loaded of 1 x 109) with the use of only a 30 watt rf amplifier for accelerating fields of 6 MV/m. The design includes the use of piezoelectric crystals for fast resonance control. Three types of control, self excited VCO, and a reference frequency driven, were tried on this cavity and we present a comparison of their performance

  1. High Amplitude Secondary Mass Drive

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-07-06

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

  2. Genus dependence of superstring amplitudes

    International Nuclear Information System (INIS)

    The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |Kn|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived

  3. Nonlinear graphene plasmonics: amplitude equation

    CERN Document Server

    Gorbach, A V

    2013-01-01

    Using perturbation expansion of Maxwell equations, the amplitude equation is derived for nonlinear TM and TE surface plasmon waves supported by graphene. The equation describes interplay between in-plane beam diffraction and nonlinerity due to light intensity induced corrections to graphene conductivity and susceptibility of dielectrics. For strongly localized TM plasmons, graphene is found to bring the superior contribution to the overall nonlinearity. In contrast, nonlinear response of the substrate and cladding dielectrics can become dominant for weakly localized TE plasmons.

  4. Amplitude dropout in coupled lasers

    International Nuclear Information System (INIS)

    We study the entrainment of coupled solid-state lasers by an external injected field. We show that the total output intensity exhibits unexpected nonmonotonic behavior as a function of the injected field and find the critical amplitude marking the transition to the low-intensity branch. In addition, we also show that substantial partial entrainment can be achieved for injected fields much weaker than that required for full entrainment

  5. Multiscalar amplitudes in perturbation theory

    International Nuclear Information System (INIS)

    It is shown that the high-multiplicity limit of amplitudes involving scalar particles (Higgs) does not respect unitary bounds at any order in perturbation theory. Possible restoration of a unitary-respecting behaviour within the Standard Model is discussed. It relies on the existence of relations that express the masses of all known elementary particles in terms of the mass of the Higgs particle. 1 fig., 14 refs

  6. Phase variation of hadronic amplitudes

    International Nuclear Information System (INIS)

    The phase variation with angle of hadronic amplitudes is studied with a view to understanding the underlying physical quantities that control it and how well it can be determined in free space. We find that unitarity forces a moderately accurate determination of the phase in standard amplitude analyses but that the nucleon-nucleon analyses done to date do not give the phase variation needed to achieve a good representation of the data in multiple scattering calculations. Models are examined that suggest its behavior near forward angles is related to the radii of the real and absorptive parts of the interaction. The dependence of this phase on model parameters is such that if these radii are modified in the nuclear medium (in combination with the change due to the shift in energy of the effective amplitude in the medium) then the larger magnitudes of the phase needed to fit the data might be attainable but only for negative values of the phase variation parameter

  7. Implementation of residual current protection in photovoltaic inverters

    OpenAIRE

    Sa?lli, Juha Timo Olavi

    2009-01-01

    The number of photovoltaic systems in distributed energy production is increasing rapidly, one advantage being pollution free energy production. Residual currents are, however, something that can disturb the operation of these systems. Residual currents are caused by the ground capacitance of the solar panels and the voltage created across this capacitance. All the choices made in the design of the system affect these problematic residual currents. The design choices include modulation techni...

  8. Simulation of Digital Modulation Techniques Using MATLAB

    OpenAIRE

    Neha Sharma, Yogendra Yadav

    2012-01-01

    In Digital modulation the message signal is in the digital form and the carrier wave is in sinusoidal form. In this technique the Amplitude, Frequency or Phase of carrier varies according to message (Baseband) signal. There are various type of digital modulation technique like Amplitude Shift Keying (ASK), Phase Shift Keying (PSK), Frequency Shift Keying (FSK), Quadature Phase Shift Keying (QPSK), Differential Phase Shift Keying (DPSK) and other digital demodulation technique. Simulation is t...

  9. RESIDUATED WEAK LATTICES

    Directory of Open Access Journals (Sweden)

    M. BASHEER AHAMED

    2010-12-01

    Full Text Available The concept of residuated lattices were developed by P. Jipsen, T. Kowalski, H. Ono and C. Tsinakis. The residuated lattices are in mathematical logic with contraction they have been investigated by R.P. Dilwoth, Krull, and M. Ward. In this paper, we introduce the residuated weak lattices by using the logical operators L , L . Finally we discuss some properties and direct product of residuated weak lattices with illustrations.

  10. Calculation of pulse amplitude in nuclear magnetic logging

    International Nuclear Information System (INIS)

    The problem of determining the amplitude of the free precession signal for the general case of placement of an NMR probe in a borehole is considered theoretically. In the analysis the probe was considered as two spools in the form of elongated frames, generally turned relative to each other at a definite angle. The expression obtained for the amplitude of the free precession signal calculates the effect of residual current, borehole diameter, size of the gap between the probe spools and the borehole walls, and the space orientation of the borehole and probe. This expression indicates that for the cases most frequently encountered the angle between the probe axis and the Earth's magnetic field direction may be calculated by interpretation, using a correction coefficient which, however, does not depend on other factors than this angle

  11. Forward amplitude in pion deuteron

    International Nuclear Information System (INIS)

    The data on total cross section for ?d scattering is analysed in terms of a single scattering calculation with Fermi motion dependence, in order to obtain a criterion to fix the value of the energy entering the two body meson nucleon amplitude. It is found that the prescription derived from the non-relativistic three body kinematics gives reasonable results. The introduction of a shift in the energy value, possibly representing nuclear binding effects, leads to a very good fitting of the data. The results are compared with those obtained in direct calculations of Faddeev equations and with the Brueckner model of fixed scatterers. (Author)

  12. Glueball Scattering Amplitudes from Holography

    CERN Document Server

    Mück, W; M\\"uck, Wolfgang; Prisco, Maurizio

    2004-01-01

    Using techniques developed in a previous paper three-point functions in field theories described by holographic renormalization group flows are computed. We consider a system of one active scalar and one inert scalar coupled to gravity. For the GPPZ flow, their dual operators create states that are interpreted as glueballs of the N=1 SYM theory, which lies at the infrared end of the renormalization group flow. The scattering amplitudes for three-glueball processes are calculated providing precise predictions for glueball decays in N=1 SYM theory. Numerical results for low-lying glueballs are included.

  13. 8-channel analog-to-digital converter based system for signal amplitude analysis of vertex detector of SVD-2 setup

    International Nuclear Information System (INIS)

    Multichannel electronic system of recording and signal amplitude analysis of semiconductor detectors is described for the experiment E-161 at a setup, namely spectrometer with vertex detector (SVD). 8-channel module of analog-to-digital conversion of AATD (amplitude analysis of vertex detector) is a base of the system. Converter sensitivity is 1 mV/indication, dynamic range is 8 binary digits, integral nonlinearity is 0.1%. The description of structure scheme and module basic parameters are given

  14. Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly

    CERN Document Server

    Nikolov, Nikolay M; Todorov, Ivan

    2013-01-01

    Configuration (x-)space renormalization of Euclidean Feynman amplitudes in a massless quantum field theory is reduced to the study of local extensions of associate homogeneous distributions. Primitively divergent graphs are renormalized, in particular, by subtracting the residue of an analytically regularized expression. Examples are given of computing residues that involve zeta values. The renormalized Green functions are again associate homogeneous distributions of the same degree that transform under indecomposable representations of the dilation group.

  15. BCFW construction of the Veneziano Amplitude

    CERN Document Server

    Fotopoulos, A

    2010-01-01

    In this note we demonstrate how one can compute the Veneziano amplitude for bosonic string theory using the BCFW method. We use an educated ansatz for the cubic amplitude of two tachyons and an arbitrary level string state.

  16. Constructing Amplitudes from Their Soft Limits

    Energy Technology Data Exchange (ETDEWEB)

    Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC

    2011-12-09

    The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.

  17. Factorization of bosonic string scattering amplitudes

    International Nuclear Information System (INIS)

    In an off-shell formulation, where scattering amplitudes for closed bosonic strings are defined as Polyakov path integrals over bordered world sheets, factorization of the amplitudes at the poles of exchanged particle states is shown in any order of perturbation theory. The same factorization is obtained for amplitudes defined via vertex operators, again for any number of loops. (orig.)

  18. Small amplitude liquid surface sloshing process detected by optical method

    Science.gov (United States)

    Miao, Yang; Wang, Shaoping

    2014-03-01

    A laser experimental set up to detect liquid surface sloshing wave excited by the instantaneous momentum was constructed. The sloshing parameters were determined by detecting the scattering light which is modulated by the surface sloshing wave. The analytical expressions which include the relationship between optical intensity and liquid surface sloshing wave and the expressions of the wave length as well as amplitude were derived theoretically. Optical patterns corresponding to static and sloshing liquid surface were obtained experimentally. The sloshing variation process including rising and damping was achieved. Both rising and damping processes are variable exponentially. The rising and damping coefficients and maximum amplitude as well as wavelength of the sloshing wave were also measured experimentally. The detection is nondestructive and real time.

  19. Waveform Sampler CAMAC Module

    International Nuclear Information System (INIS)

    A Waveform Sampler Module (WSM) for the measurement of signal shapes coming from the multi-hit drift chambers of the SLAC SLC detector is described. The module uses a high speed, high resolution analog storage device (AMU) developed in collaboration between SLAC and Stanford University. The AMU devices together with high speed TTL clocking circuitry are packaged in a hybrid which is also suitable for mounting on the detector. The module is in CAMAC format and provides eight signal channels, each recording signal amplitude versus time in 512 cells at a sampling rate of up to 360 MHz. Data are digitized by a 12-bit ADC with a 1 ?s conversion time and stored in an on-board memory accessible through CAMAC

  20. Waveform sampler CAMAC module

    International Nuclear Information System (INIS)

    A Waveform Sampler Module (WSM) for the measurement of signal shapes coming from the multi-hit drift chambers of the SLAC SLD detector is described. The module uses a high speed, high resolution analog storage device (AMU) developed in collaboration between SLAC and Stanford University. The AMU devices together with high speed TTL clocking circuitry are packaged in a hybrid which is also suitable for mounting on the detector. The module is in CAMAC format and provides eight signal channels, each recording signal amplitude versus time in 512 cells at a sampling rate of up to 360 MHz. Data are digitized by a 12-bit ADC with a 1 ?s conversion time and stored in an on-board memory accessible through CAMAC

  1. Calcium: amplitude, duration, or location?

    Science.gov (United States)

    Evans, R C; Blackwell, K T

    2015-02-01

    Calcium plays a role in long-term plasticity by triggering postsynaptic signaling pathways for both the strengthening (LTP) and weakening (LTD) of synapses. Since these are opposing processes, several hypotheses have been developed to explain how calcium can trigger LTP in some situations and LTD in others. These hypotheses fall broadly into three categories, based on the amplitude of calcium concentration, the duration of the calcium elevation, and the location of the calcium influx. Here we review the experimental evidence for and against each of these hypotheses and the recent computational models utilizing each. We argue that with new experimental techniques for the precise visualization of calcium and new computational techniques for the modeling of calcium diffusion, it is time to take a new look at the location hypothesis. PMID:25745102

  2. Holonomy-flux spinfoam amplitude

    CERN Document Server

    Perini, Claudio

    2012-01-01

    We introduce a holomorphic representation for the Lorentzian EPRL spinfoam on arbitrary 2-complexes. The representation is obtained via the Ashtekar-Lewandowski-Marolf-Mour\\~ao-Thiemann heat kernel coherent state transform. The new variables are classical holonomy-flux phase space variables $(h,X)\\simeq \\mathcal T^*SU(2)$ of Hamiltonian loop quantum gravity prescribing the holonomies of the Ashtekar connection $A=\\Gamma + \\gamma K$, and their conjugate gravitational fluxes. For small heat kernel `time' the spinfoam amplitude is peaked on classical space-time geometries, where at most countably many curvatures are allowed for non-zero Barbero-Immirzi parameter. We briefly comment on the possibility to use the alternative flipped classical limit.

  3. Learning Modules for an Electronics Curriculum

    Science.gov (United States)

    This site features twenty-four interactive learning modules and fifteen pilot modules offering educational technologies on electronics. All online modules run as Shockwave videos in a browser environment and a utilization guide is provided. The circuits signals and systems communications CCLI Modules available on this site include: Generic Voltage Divider, Caps and Inductors, Circuit Solver, Op-Amps CAD, 2nd Order Systems, Phasors in Circuit Analysis, Filters Introduction, Filters CAD, Time/Frequency Laplace Domains, Fourier Signal Generator, Wave Chooser, Fourier Transform, Convolution, Band Pass Filters, Sampling, Learning Styles Survey, Amplitude Modulation, A/D Conversion, Analog Modulation, Digital Modulation, Pulse Modulation, TDM, Frequency Division Multiplexing, and FDMA. The CCLI Pilot Modules include: DC Circuit (w/ Voltage Source), DC Circuit (w/ Current Source), Nodal Analysis, AC Voltage Regulation, Power Factor Correction, Transformer Utilization, Vectors, Pole-Zero Plots, Exploring Connectivity, and Exploring Resistance.

  4. Interaction of kink-lattice solitons with small-amplitude waves in finite-size superlattices

    International Nuclear Information System (INIS)

    Propagation of large-amplitude electromagnetic fields and their interactions with small-amplitude waves in finite superlattices are considered in the framework of the sine-Gordon theory. Finite-size effects result in modulating the large-amplitude fields to a lattice of kinked waves. This kink-lattice wave displays both a soliton feature and the particle property typical to nonlinear topological excitations. The interaction of the kink-lattice soliton with weak electromagnetic waves reveals an unusual number (exactly three) of bound states, which is attributed to the finite size of the propagation medium. (author)

  5. Phase and Amplitude Responses of Narrow-Band Optical Filter Measured by Microwave Network Analyzer

    CERN Document Server

    Wang, H C; Wang, Hsi-Cheng; Ho, Keang-Po

    2006-01-01

    The phase and amplitude responses of a narrow-band optical filter are measured simultaneously using a microwave network analyzer. The measurement is based on an interferometric arrangement to split light into two paths and then combine them. In one of the two paths, a Mach-Zehnder modulator generates two tones without carrier and the narrow-band optical filter just passes through one of the tones. The temperature and environmental variations are removed by separated phase and amplitude averaging. The amplitude and phase responses of the optical filter are measured to the resolution and accuracy of the network analyzer.

  6. Residual gas analysis

    International Nuclear Information System (INIS)

    Determination of the residual gas composition in vacuum systems by a special mass spectrometric method was presented. The quadrupole mass spectrometer (QMS) and its application in thin film technology was discussed. Results, partial pressure versus time curves as well as the line spectra of the residual gases in case of the vaporization of a Ti-Pd-Au alloy were demonstrated together with the possible construction schemes of QMS residual gas analysers. (Sz.J.)

  7. Study of new modulation data-transmission formats for dispersion-controlled high-bit-rate fibreoptic communication lines

    International Nuclear Information System (INIS)

    The results of simulation of the propagation of optical signals in a multichannel high-bit-rate fibreoptic communication line with a combined scheme for amplifying optical signals based on new modulation data-transmission formats are presented. A comparative characteristic of formats with the amplitude and phase modulations of the electromagnetic-wave carrier is presented. The results of numerical simulation show that phase-modulation formats have a considerable advantage over amplitude formats. The use of phase-modulation formats leads to an increase in the maximum range of high-quality communications by a factor of three on average compared to amplitude-modulation formats. It is shown that optimal propagation regimes both in the case of amplitude-modulation and phase-modulation formats are realised for the normal (negative) group-velocity dispersion. However, the dispersion value for amplitude-modulation formats proves to be considerably greater than for phase-modulation formats. (optical communication)

  8. Crack detection using nonlinear acoustics and piezoceramic transducers—instantaneous amplitude and frequency analysis

    International Nuclear Information System (INIS)

    This paper investigates the nonlinear vibro-acoustic modulation technique for damage detection in metallic structures. Surface-bonded, low-profile piezoceramic actuators are used to introduce a high-frequency ultrasonic wave and low-frequency modal vibration into an aluminium specimen. The response of the vibro-acoustic interaction is monitored by a third low-profile piezoceramic transducer. In contrast to previous applications analysing the response in the frequency domain, current investigations focus on the instantaneous characteristics of the response using the Hilbert–Huang transform. The study shows that both modulations, i.e. amplitude and frequency, are present in the acoustical responses when the aluminium plate is cracked. The intensity of amplitude modulation correlates far better with crack lengths than the intensity of frequency modulations

  9. Amplitude spectrum compensation and phase spectrum correction of seismic data based on the generalized S transform

    Science.gov (United States)

    Zhou, Huai-Lai; Wang, Jun; Wang, Ming-Chun; Shen, Ming-Cheng; Zhang, Xin-Kun; Liang, Ping

    2014-12-01

    We propose a method for the compensation and phase correction of the amplitude spectrum based on the generalized S transform. The compensation of the amplitude spectrum within a reliable frequency range of the seismic record is performed in the S domain to restore the amplitude spectrum of reflection. We use spectral simulation methods to fit the time-dependent amplitude spectrum and compensate for the amplitude attenuation owing to absorption. We use phase scanning to select the time-, space-, and frequencydependent phases correction based on the parsimony criterion and eliminate the residual phase effect of the wavelet in the S domain. The method does not directly calculate the Q value; thus, it can be applied to the case of variable Q. The comparison of the theory model and field data verify that the proposed method can recover the amplitude spectrum of the strata reflectivity, while eliminating the effect of the residual phase of the wavelet. Thus, the wavelet approaches the zero-phase wavelet and, the seismic resolution is improved.

  10. Faraday patterns in Bose-Einstein condensates. Amplitude equation for rolls in the parametrically driven, damped Gross-Pitaevskii equation

    OpenAIRE

    Valcarcel, German J.

    2002-01-01

    The parametrically driven, damped Gross-Pitaevskii equation, which models Bose-Einstein condensates in which the interatomic s-wave scattering length is modulated in time, is shown to support spatially modulated states in the form of rolls. A Landau equation with broken phase symmetry is derived, which governs the dynamics of the roll amplitude.

  11. Least Squares Residuals and Minimal Residual Methods.

    Czech Academy of Sciences Publication Activity Database

    Liesen, J.; Rozložník, Miroslav; Strakoš, Zden?k

    2002-01-01

    Ro?. 23, ?. 5 (2002), s. 1503-1525. ISSN 1064-8275 R&D Projects: GA AV ?R IAA1030103 Institutional research plan: AV0Z1030915 Keywords : linear systems * least squares problems * Krylov subspace methods * minimal residual methods * GMRES * convergence * rounding errors Subject RIV: BA - General Mathematics Impact factor: 1.291, year: 2002

  12. Notes on amplitude function mismatch

    International Nuclear Information System (INIS)

    The design process of modern high-energy synchrotrons involves the development of the accelerator lattice in pieces, typically an arc made up of repetitive cells interrupted by occasional matched insertions for injection, extraction, acceleration and various other systems required by the facility. The focusing elements of an insertion must be such that the periodic amplitude functions at the ends of the insertion match those of the cells on either side of the insertion. How well this match has to be and its sensitivity to the global betatron tunes of the accelerator as well as the particle momentum are the underlying themes of this report. Many of the relationships also are of use to the designers of beamlines which are used to transport and inject beams into a synchrotron. Most of the content of this paper is not new to the accelerator physics community, but we thought it would be useful to place this important, basic information all in one place. Besides the classic work of Courant and Snyder, our sources include other papers, internal reports, and numerous discussions with our colleagues

  13. Discontinuities of multi-Regge amplitudes

    CERN Document Server

    Fadin, V S

    2014-01-01

    In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for $n$-gluon amplitudes in the planar $N$=4 SYM at $n\\ge 6$. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.

  14. The Trace Formula of the Spinoriel Amplitude

    OpenAIRE

    Mekhfi, M.

    2009-01-01

    We re express the fermion's probability amplitude as a trace over spinor indices, which formulation surprisingly does not exist in literature. This formulation puts the probabilty amplitude and the the probabilty(squared amplitude) of a given process on equal footing at the compuational level and this is our principal motivation to write the present paper. We test the power of the trace formula in three applications: Calculation of the charge-current of fermions by using sym...

  15. Development of an electro-optic super modulator

    International Nuclear Information System (INIS)

    Full text: Optical phase modulators and amplitude modulators are commonplace in modern laser laboratories. In this talk, we present the development of a device that produces both amplitude modulation (AM) and phase modulation (PM), with a selectable phase relation between the two, on a single free-space Gaussian beam. We term this device a 'super modulator. The device is a version of the Mach-Zehnder modulator, where a beam is split, then separately phase modulated and recombined. Previous work has concentrated on one specific operating point, where the relative modulation phases and the interferometer phase are set to generate single sideband modulation, equivalent to an equal amount of AM and PM in quadrature. Here we are interested in the entire parameter space of amplitude modulation strength, phase modulation strength, and the phase relation between the two. The need for such a super modulator has arisen in the context of control systems for gravitational wave detection interferometers. Typical locking systems are based on the Pound-Drever-Hall method of locking which uses phase modulation. In principle, a super modulator could be used in a PDH configuration, when the locking point of the device will be tunable according to the quantity of AM injected (along with the obligatory PM) into the device

  16. Relaxation of Residual Stress Part 2: Relaxation of Stage 2

    Directory of Open Access Journals (Sweden)

    Omar S. Zaroog

    2009-01-01

    Full Text Available Problem statement: Compressive residual stress induced by surface treatment such as shot peening increased component?s fatigue life. However the initial induced residual stresses relax during component operating life and it is important to consider the relaxation in the design. Approach: In this study, a 2024-T351 aluminum alloy specimens were shot peened into three shot peening intensities condition to induce compressive residual stresses. Then fatigue test for two loads was performed for the 10, 1000 and 10000 cyclic loads. The initial residual stresses at the initial condition and after 10, 1000 and 10000 cycle of fatigue loading were measured using X-ray diffraction method. Results: The results showed that the relaxation of the residual stress for the load 15.5 kN is less than the relaxation of the load 30 kN for the three shot peening intensity. The maximum relaxation for load 15.5 kN is 46% of the initial residual stress at 10000 cycles for intensity 0.009 A while the maximum relaxation for load 30 kN is 54% at 10000 cycles for the intensity of 0.0054% A. this result indicated that the residual stress relaxation depended on the load amplitude. Conclusion: The initial residual stress did not remain stable during the component?s fatigue life. Within the second phase relaxation, micro-plastic strains accumulating from cycle to cycle. The residual stress relaxation for second phase is in logarithmic relationship.

  17. The quadrupole amplitude in the ?N ? ? transition

    International Nuclear Information System (INIS)

    The presence of the tensor part of the color hyperfine interactions between quarks leads to a small electric quadrupole amplitude in the ?N ? ? excitation. The difficulties in extracting this small amplitude with an appreciable background contribution from experiment is discussed. Furthermore, it is demonstrated that the available pion photoproduction data have a low sensitivity to the resonant (isospin 3/2) electric quadrupole amplitude, E1+(3/2). The authors show that ?p ? ?0p cross sections near 0 degrees and 180 degrees and also those with polarized ?-rays near 90 degrees will have the maximum sensitivity to the resonant E1+(3/2) amplitude. 23 refs., 3 figs

  18. Modulation light efficiency of diffractive lenses displayed in a restricted phase-mostly modulation display.

    Science.gov (United States)

    Moreno, Ignacio; Iemmi, Claudio; Márquez, Andrés; Campos, Juan; Yzuel, María J

    2004-12-01

    We present an analysis of the diffraction efficiency of diffractive lenses displayed on spatial light modulators that depends on the modulation response of the display. An ideal display would produce continuous phase-only modulation, reaching a maximum phase-modulation depth of 2pi. We introduce the concept of modulation diffraction efficiency that accounts for the effect of nonlinearities only in the phase modulation of the display. We review a diffractive model with which to evaluate this modulation efficiency, including modulation defects such as nonlinear phase modulation, coupled amplitude modulation, phase quantization, and a limited modulation depth. We apply this diffractive model to Fresnel lenses and show that these modulation defects produce a lens multiplex effect. Finally we demonstrate that the application of a minimum Euclidean projection principle leads to high modulation diffraction efficiency even if the phase-modulation depth is much less than 2pi. We demonstrate that the modulation efficiency can exceed 90% for a modulation depth of 1.4pi and can exceed 40% (the equivalent for a binary phase element) for a modulation depth of only 0.7pi. Experimental results from use of a twisted nematic liquid-crystal display are presented to confirm these conclusions. PMID:15619838

  19. Evidence of a transverse Langmuir modulational instability in a space plasma

    International Nuclear Information System (INIS)

    Electric field amplitude modulations of Langmuir waves were observed in the auroral ionosphere. The data are consistent with a transverse modulational instability resonant with lower hybrid or ion Bernstein waves. The envelopes appear to have been nearly saturated

  20. Thiometon residues in cucumber

    International Nuclear Information System (INIS)

    In the Islamic Republic of Iran, vegetables are treated repeatedly with pesticides to control pests and diseases. Crops harvested shortly after pesticide application are probably contaminated by pesticides that are toxic to humans. Pesticide residues in vegetables are especially important, since these crops are ingested directly by humans. In recent years, farmers have been using more persistent pesticides to protect their crops because of increasing pesticide prices. Field trials were carried out to determine the residues of thiometon, a systemic insecticide used on cucumber. In 1993 and 1994, Ekatin (a 25% thiometon emulsifiable concentrate) was applied with a knapsack sprayer to cucumber (var. Daminus) at late flowering at dilutions of 1:1000 and 2:1000. Plots were 25 m2 in three replicates and were sampled 3, 6, 10, 15, 19 and 24 days after application. The samples were extracted with acetonitrile and cleanup was carried out using thin layer chromatography. Thiometon and two metabolites (thiometon sulphide and thiometon sulphone) were analyzed by gas chromatography. In 1994, the amount of thiometon sulphide determined 24 days treatment was 2 ppm in the peeled cucumber, which exceeded the maximum residue limit of 0.5 ppm. The total thiometon residues were higher in the peeled cucumber than those in the cucumber peel. Thus, peeling is ineffective for reducing the systemic residues of thiometon. Likewise, in this experiment lower dilution caused higher ratxperiment lower dilution caused higher rather than lower thiometon residues in cucumber. The rapid disappearance of thiometon residues 2 weeks after treatment suggests that storing cucumbers at room temperature may be a better strategy for reducing excessive thiometon residues. Alternatively, a contact insecticide could be used. Thus, the bulk of the surface residues could be removed by washing or peeling. (author). 5 refs, 4 figs

  1. Travel time and amplitude analysis in seismic tomography

    Science.gov (United States)

    Bregman, Nina D.; Chapman, Christopher H.; Bailey, Richard C.

    1989-06-01

    In cross-hole tomography straight lines connecting the source and receiver are often used to approximate the true ray paths, thus linearizing the inverse problem. A recent paper by Bregman et al. (1989a) has shown that this approximation may be very poor in the regions of greatest interest where large velocity gradients cause significant ray curvature. The interpretation method presented by Bregman et al. (1989a) iteratively ray traces and updates the velocity model with model perturbations obtained by a damped least squares inversion of the travel time residuals. This paper presents a modification of the travel time tomography method so that it may be applied to the inversion of first motion amplitudes for inverse quality factor Q-1. After determining the velocity structure using travel time tomography the amplitudes are inverted using a similar scheme. No additional ray tracing is required for the amplitude inversions. The effect of the velocity structure previously determined through travel time tomography is taken into account so that amplitude variations due to the focusing and defocusing effects of the velocity structure are not interpreted as being due to attenuation structure. Both the travel time and amplitude tomography methods are applied here to field data from a cross-hole experiment in crystalline rock (Wong et al., 1983). The frequency range of the seismograms is 1-6.6 kHz, allowing resolution of velocity structure on a scale of several meters. The resulting velocity image shows good agreement with other geological and geophysical data. Reversing the model by placing the model boreholes on opposite sides relative to the original reconstruction yields almost identical results, indicating that the interpolation scheme used in the forward modeling has not biased the final model. Synthetic Maslov seismograms calculated for the derived velocity model agree well with the waveform data, further confirming the validity of the model. In addition, the amplitude tomography results place absorptive regions in the same location as the most pronounced low-velocity features which correlate with fractures in the boreholes. Highly transmissive regions also correlate well with high-velocity regions.

  2. Modulation masking produced by complex-tone modulators

    DEFF Research Database (Denmark)

    Ewert, Stephan; Verhey, J.L.

    2003-01-01

    Thresholds were measured for detecting sinusoidal amplitude modulation in the presence of a complex-tone masker modulation. Both modulations were applied to the same sinusoidal carrier. Two different masker modulations were used: (i) a pair of components beating at the difference frequency and (ii) a three-tone complex producing a sinusoidal amplitude modulation of the modulation depth at the difference frequency between adjacent components. Both maskers show a periodicity in the waveform that is not contained in the envelope spectrum itself but can be observed when the envelope of the envelope, referred to as the "venelope" [Ewert et al., J. Acoust. Soc. Am. 112. 2921-2931 (2002)], is calculated. For a signal frequency equal to the masker-venelope periodicity, modulation depth at threshold was measured as a function of the signal phase relative to the phase of the masker-venelope component. Signal frequencies of 5, 30, and 90 Hz were used. It was found that masking was phase dependent for all three signal frequencies. Thresholds were lower for the in-phase condition, where maxima in the signal waveform coincided with maxima in the masker-venelope waveform, than for the antiphase condition. The maximum threshold difference was 15 dB. The results are in contrast to recent data [Moore et al., J. Acoust. Soc. Am. 106, 908-918 (1999)], where lowest thresholds were reported for the antiphase condition in a similar experiment. The present data are in line with the idea that a nonlinearity prior to a modulation filterbank extracts the venelope of the masker modulator. However, a compressive nonlinearity such as that associated with the processing on the basilar membrane cannot account for the empirical findings, since it predicts the opposite phase effect.

  3. Suppression of backreflection noise in a resonator integrated optic gyro by hybrid phase-modulation technology.

    Science.gov (United States)

    Feng, Lishuang; Lei, Ming; Liu, Huilan; Zhi, Yinzhou; Wang, Junjie

    2013-03-10

    A method to suppress backreflection noise due to facet reflection in a resonator integrated optic gyro (RIOG) is demonstrated using hybrid phase-modulation technology (HPMT). First, calculations are carried out to evaluate the effect of the backreflection. Although its amplitude has been remarkably decreased by angle polishing, residual backreflection noise is still a severe factor in RIOGs. Next, a hybrid phase-modulation method to eliminate the backreflection noise is constructed, and the frequency spectra of the photodetector outputs before and after adopting HPMT are analyzed. Theoretical analysis shows that the backreflection noise spectra will split from each other as a result of the hybrid phase modulation. In association with the pectinate-filter characteristics of digital correlation detection, the backreflection noise can be suppressed. Finally, the RIOG experimental setup is established and compared with opposite-slope triangle phase-modulation technology. HPMT has the advantage of suppressing backreflection noise, with the RIOG bias stability greatly improved from 2.34 to 0.22 deg/s (10 s integration time). PMID:23478771

  4. BCFW construction of the Veneziano amplitude

    International Nuclear Information System (INIS)

    In this paper we demonstrate how one can compute the Veneziano amplitude for bosonic string theory using the Britto-Cachazo-Feng-Witten method. We use an educated ansatz for the cubic amplitude of two tachyons and an arbitrary level string state.

  5. On the nullification of threshold amplitudes

    CERN Document Server

    Gonera, J

    2002-01-01

    The nullification of threshold amplitudes is considered within the conventional framework of quantum field theory. The relevant Ward identities for the reduced theory are derived both on path-integral and diagrammatic levels. They are then used to prove the vanishing of tree-graph threshold amplitudes.

  6. Automation of loop amplitudes in numerical approach

    International Nuclear Information System (INIS)

    An automatic calculating system GRACE-L1 of one-loop Feynman amplitude is reviewed. This system can be applied to 2 to 2-body one-loop processes. A sample calculation of 2 to 3-body one-loop amplitudes is also presented. (orig.)

  7. Consistent Off-Shell Tree String Amplitudes

    OpenAIRE

    Liccardo, A.; Pezzella, F.; Marotta, R.

    1999-01-01

    We give a construction of off-shell tree bosonic string amplitudes, based on the operatorial formalism of the $N$-string Vertex, with three external massless states both for open and closed strings by requiring their being projective invariant. In particular our prescription leads, in the low-energy limit, to the three-gluon amplitude in the usual covariant gauge.

  8. On off-shell bosonic string amplitudes

    OpenAIRE

    Cappiello, L.; Marotta, R.; Pettorino, R.; Pezzella, F.

    1998-01-01

    We give a simple prescription for computing, in the framework of the bosonic string theory, off-shell one-loop amplitudes with any number of external massless particles, both for the open and for the closed string. We discuss their properties and, in particular, for the two-string one-loop amplitudes we show their being transverse.

  9. Symbolic calculation of multiparticle Feynman amplitudes

    OpenAIRE

    Cherzor, P.

    2003-01-01

    Using the newly modified method developed for symbolic evaluation of Feynman amplitudes we examine two processes $2\\to 2$ (including a case of Majorana fermions) at a tree level. Constructing special polarization basis for spinor particles, we obtain compact expressions for helicity amplitudes. We present the regular way for simplification of evaluated symbolic expressions.

  10. A New Approach for Analytic Amplitude Calculations

    OpenAIRE

    Qiao, Cong-feng

    2003-01-01

    We present a method for symbolic calculation of Feynman amplitudes for processes involving both massless and massive fermions. With this approach fermion strings in a specific amplitude can be easily evaluated and expressed as basic Lorentz scalars. The new approach renders the symbolic calculation of some complicated physical processes more feasible and easier, especially with the assistance of algebra manipulating codes for computer.

  11. Interfacial residual thermal strain

    Science.gov (United States)

    Kasen, M.; Santoyo, R.

    A method has been developed for assessing the influence of polymer chemical composition and of processing parameters on the magnitude of residual stress developed in glass-fibre-reinforced composites subjected to various cure cycles and subsequently cooled to cryogenic temperatures. The test method was applied to nine resin types, including epoxy, vinyl ester, polyester, cyanate ester and phenolic formulations. Results suggest that polyester resin develops substantially less overall residual strain than do the other resin systems.

  12. Conformal Modules

    OpenAIRE

    Cheng, Shun-jen; Kac, Victor

    1997-01-01

    In this paper we study a class of modules over infinite-dimensional Lie (super)algebras, which we call conformal modules. In particular we classify and construct explicitly all irreducible conformal modules over the Virasoro and the N=1 Neveu-Schwarz algebras, and over the current algebras.

  13. Pulse amplitude analysis of rare events measured in heavy-ion-induced nuclear reactions

    International Nuclear Information System (INIS)

    A complex analysis has been performed on the energy amplitude signals corresponding to rare events observed in nuclear reactions aimed at the synthesis of super heavy elements (SHE). In a few cases, the values of the amplitudes are anomalous. The reaction products in the analyzed experiments were detected by a PIPS detector characterized by a significant pulse height defect (PHD) associated with the detection of evaporation residues (EVR) and fission fragments (FF). After correction, the observations of anomalous EVR energy values provide a reason to reject an entire event

  14. Evidence for modulation of osteocalcin containing gamma-carboxyglutamic acid residues synthesis by insulin-like growth factor-I and vitamin K2 in human osteosarcoma cell line MG-63.

    Science.gov (United States)

    Kudo, Y; Iwashita, M; Takeda, Y; Muraki, T

    1998-04-01

    The effect of insulin-like growth factor-I (IGF-I) and 2-methyl-3-all-trans-tetraphenyl-1,4-naphtoquinone (vitamin K2) on the synthesis of osteocalcin containing gamma-carboxyglutamic acid (Gla) residues which is the physiologically relevant form in bone metabolism was studied in cultured human osteoblast-like (MG-63) cells. Both IGF-I and vitamin K2 stimulated 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-induced osteocalcin containing Gla secretion in a concentration-dependent manner. This stimulatory effect of IGF-I and vitamin K2 was additive. Vitamin K2-enhanced osteocalcin containing Gla secretion was selectively suppressed by 3-(alpha-acetonyl-benzyl)-4-hydroxy-coumarin (warfarin). The stimulatory effect of IGF-I was completely abolished by the presence of cycloheximide; in contrast the effect of vitamin K2 was still observed in the presence of cycloheximide. Treatment of MG-63 cells with IGF-I caused an approximately 2.2-fold increase in osteocalcin mRNA levels (determined by reverse transcription-polymerase chain reaction). Vitamin K2 had no effect on either the stimulation of mRNA level by IGF-I or the basal level. IGF-I-stimulated osteocalcin containing Gla secretion was inhibited by one of its binding proteins (insulin-like growth factor binding protein-4) in a concentration-dependent manner. These findings suggest that the modes of action of IGF-I and vitamin K2 on 1.25(OH)2D3-induced osteocalcin containing Gla secretion in MG-63 cells are different. PMID:9578515

  15. Paralleled Phase Shifted Carrier Pulse Width Modulation (PSCPWM) Schemes - A Fundamental Analysis.

    DEFF Research Database (Denmark)

    Christensen, Frank Schwartz; Frederiksen, Thomas Mansachs

    1999-01-01

    The paper presents a fundamental analysis of modulation schemes and their spectral aspects for a range of powerstage topologies, from a simple 2-level switching leg to more complex multi-level switching topologies. A family of modulation schemes are introduced and the double Fourier series based analysis leads to a redefinition of pulsewidth modulation including amplitude modulation.

  16. On the cascade mechanism of short surface wave modulation

    OpenAIRE

    Charnotskii, M.; Naugolnykh, K.; Ostrovsky, L.; Smirnov, A.

    2002-01-01

    Modulation of short surface ripples by long surface or internal waves by a cascade mechanism is considered. At the first stage, the orbital velocity of the long wave (LW) adiabatically modulates an intermediate length nonlinear gravity wave (GW), which generates a bound (parasitic) capillary wave (CW) near its crest in a wide spatial frequency band. Due to strong dependence of the CW amplitude on that of the GW, the resulting ripple modulation by LW can be strong. Adiabatic modulation ...

  17. Cascaded uncoupled dual-ring modulator

    CERN Document Server

    Gu, Tingyi; Wong, Chee Wei; Dong, Po

    2014-01-01

    We demonstrate that by coherent driving two uncoupled rings in same direction, the effective photon circulating time in the dual ring modulator is reduced, with increased modulation quality. The inter-ring detuning dependent photon dynamics, Q-factor, extinction ratio and optical modulation amplitude of two cascaded silicon ring resonators are studied and compared with that of a single ring modulator. Experimentally measured eye diagrams, together with coupled mode theory simulations, demonstrate the enhancement of dual ring configuration at 20 Gbps with a Q ~ 20,000.

  18. Residual Stress Studies Using the Cairo Fourier Diffractometer Facility

    International Nuclear Information System (INIS)

    The present paper deals with residual stress studies using the Cairo Fourier diffractometer facility CFDF. The CFDF is a reverse - time of -flight (RTOF) diffractometer; applies a Fourier chopper. The measurements were performed for copper samples in order to study the residual stress after welding. The maximum modulation of the Fourier chopper during the measurements was 136 khz; leading to a time resolution half-width of about 7 ? s. It has been found from the present measurements that, the resulting diffraction spectra could be successfully used for studying the residual stress; in the wavelength range between 0.7-2.9 A degree at ? 0.45 % relative resolution

  19. ?NNN-NNN problem: Connectedness, transition amplitudes, and quasiparticle approximation

    International Nuclear Information System (INIS)

    In this paper we review the present status of the ?NNN-NNN problem. In particular, we reconsider the chain-labeled approach recently proposed by us, and identify a class of graphs, previously overlooked, which prevents the kernel of the corresponding ?NNN-NNN equations from being connected. We propose some approximate schemes, yielding connected-kernel equations. A generalization of the residue method allows us to relate the transition amplitudes for the coupled ?NNN-NNN system to the chain-labeled formalism. The quasiparticle approach is extended to the present situation, where emission/absorption of particles is allowed. The open problems for the ?NNN-NNN system in light of the present and of previous approaches are finally discussed. copyright 1997 The American Physical Society

  20. PERFORMANCE ANALYSIS OF MIMO-SPACE TIME BLOCK CODING WITH DIFFERENT MODULATION TECHNIQUES

    Directory of Open Access Journals (Sweden)

    Shubhangi Chaudhary

    2012-03-01

    Full Text Available MIMO Diversity is the technique which takes the advantage of multipath and mitigates the effect of fading and increases signal strength. Space Time Block code (STBC is used in Multiple Input Multiple Output (MIMO system to improve the performance by maximizing diversity gain. In this paper Math Works-SIMULINK platform is used for simulation. The performance of MIMO, Space Time Block Code (STBC with different modulations, such as M-ary Phase Shift Keying (M-PSK, Binary phase shift modulation (BPSK, Quadrature phase shift modulation (QPSK, 8-PSK, and M-ary Quadrature Amplitude Modulation (M-QAM, 16-Quadrature Amplitude modulation (16-QAM and 64-Quadrature Amplitude modulation (64QAM, 256-Quadrature Amplitude modulation (256-QAM are studied on the basis of bit error rate (BER, signal-to-noise ratio (SNR and error probability.

  1. Module Configuration

    Science.gov (United States)

    Oweis, Salah (Ellicott City, MD); D'Ussel, Louis (Bordeaux, FR); Chagnon, Guy (Cockeysville, MD); Zuhowski, Michael (Annapolis, MD); Sack, Tim (Cockeysville, MD); Laucournet, Gaullume (Paris, FR); Jackson, Edward J. (Taneytown, MD)

    2002-06-04

    A stand alone battery module including: (a) a mechanical configuration; (b) a thermal management configuration; (c) an electrical connection configuration; and (d) an electronics configuration. Such a module is fully interchangeable in a battery pack assembly, mechanically, from the thermal management point of view, and electrically. With the same hardware, the module can accommodate different cell sizes and, therefore, can easily have different capacities. The module structure is designed to accommodate the electronics monitoring, protection, and printed wiring assembly boards (PWAs), as well as to allow airflow through the module. A plurality of modules may easily be connected together to form a battery pack. The parts of the module are designed to facilitate their manufacture and assembly.

  2. Relativistic amplitudes in terms of wave functions

    International Nuclear Information System (INIS)

    In the framework of the invariant diagram technique which arises at the formulation of the fueld theory on the light front the question about conditions at which the relativistic amplitudes may be expressed through the wave functions is investigated. The amplitudes obtained depend on four-vector ?, determining the light front surface. The way is shown to find such values of the four-vector ?, at which the contribution of diagrams not expressed through wave functions is minimal. The investigation carried out is equivalent to the study of the dependence of amplitudes of the old-fashioned perturbation theory in the in the infinite momentum frame on direction of the infinite momentum

  3. Helicity Amplitudes and Angular Decay Distributions

    CERN Document Server

    Körner, J G

    2014-01-01

    I discuss how to obtain angular decay distributions for sequential cascade decays using helicity methods. The angular decay distributions follow from a reasonably simple master formula involving bilinear forms of helicity amplitudes and Wigner's $d$ functions. I discuss in some detail the issue of gauge invariance for off-shell gauge bosons. As a technical exercise I calculate the linear relation between the helicity amplitudes and the invariant amplitudes of semileptonic and rare baryon decays. I discuss two explicit examples of angular decay distributions for (i) the decay $t\\to b+W^+(\\to \\ell^+\

  4. Observational studies of Cepheid amplitudes. II Metallicity dependence of pulsation amplitudes

    CERN Document Server

    Szabados, László

    2011-01-01

    Physical and phenomenological properties (radius, luminosity, shape of the light curve, etc.) of Cepheids strongly depend on the pulsation period, with the exception of the pulsation amplitude. A possible factor causing a wide range of pulsation amplitudes might be the different atmospheric metallicities of individual Cepheids. We studied the influence exerted by the atmospheric iron content, [Fe/H], on the pulsational amplitude of Galactic Cepheids. We searched for correlations between the [Fe/H] value and both the observed amplitudes and amplitude related parameters. The amplitude of the Cepheid pulsation slightly decreases with increasing iron abundance. This effect is more pronounced for the radial velocity variations and for the shorter pulsation periods. The wavelength dependence of photometric amplitudes is also found to be sensitive to the metallicity. Some of these effects are not consequences of differential line blanketing. Based on the calibrations of the metallicity sensitivity relationships, we ...

  5. Obliquity Modulation of the Incoming Solar Radiation

    Science.gov (United States)

    Liu, Han-Shou; Smith, David E. (Technical Monitor)

    2001-01-01

    Based on a basic principle of orbital resonance, we have identified a huge deficit of solar radiation induced by the combined amplitude and frequency modulation of the Earth's obliquity as possibly the causal mechanism for ice age glaciation. Including this modulation effect on solar radiation, we have performed model simulations of climate change for the past 2 million years. Simulation results show that: (1) For the past 1 million years, temperature fluctuation cycles were dominated by a 100-Kyr period due to amplitude-frequency resonance effect of the obliquity; (2) From 2 to 1 million years ago, the amplitude-frequency interactions. of the obliquity were so weak that they were not able to stimulate a resonance effect on solar radiation; (3) Amplitude and frequency modulation analysis on solar radiation provides a series of resonance in the incoming solar radiation which may shift the glaciation cycles from 41-Kyr to 100-Kyr about 0.9 million years ago. These results are in good agreement with the marine and continental paleoclimate records. Thus, the proposed climate response to the combined amplitude and frequency modulation of the Earth's obliquity may be the key to understanding the glaciation puzzles in paleoclimatology.

  6. Global Residues and Two-Loop Hepta-Cuts

    CERN Document Server

    Sogaard, Mads

    2013-01-01

    We derive remarkably compact analytic expressions for coefficients of master integrals with two-loop crossed box topology in four-point gauge theory amplitudes with arbitrary adjoint matter and massless kinematics, thereby providing additional steps towards automated computation of the full amplitude. The coefficients are uniquely obtained by assembling residues extracted through integration on linear combinations of higher-dimensional tori encircling global poles of the loop integrand. Several explicit calculations are provided. We also establish exact equivalence of our results and master integral coefficients recently obtained via integrand-level reduction in any renormalizable gauge theory.

  7. Covariant Residual Entropy

    CERN Document Server

    Hubeny, Veronika E

    2014-01-01

    A recently explored interesting quantity in AdS/CFT, dubbed 'residual entropy', characterizes the amount of collective ignorance associated with either boundary observers restricted to finite time duration, or bulk observers who lack access to a certain spacetime region. However, the previously-proposed expression for this quantity involving variation of boundary entanglement entropy (subsequently renamed to 'differential entropy') works only in a severely restrictive context. We explain the key limitations, arguing that in general, differential entropy does not correspond to residual entropy. Given that the concept of residual entropy as collective ignorance transcends these limitations, we identify two correspondingly robust, covariantly-defined constructs: a 'strip wedge' associated with boundary observers and a 'rim wedge' associated with bulk observers. These causal sets are well-defined in arbitrary time-dependent asymptotically AdS spacetimes in any number of dimensions. We discuss their relation, spec...

  8. Motivic Multiple Zeta Values and Superstring Amplitudes

    CERN Document Server

    Schlotterer, O

    2012-01-01

    The structure of tree-level open and closed superstring amplitudes is analyzed. For the open superstring amplitude we find a striking and elegant form, which allows to disentangle its alpha'-expansion into several contributions accounting for different classes of multiple zeta values. This form is bolstered by the decomposition of motivic multiple zeta values, i.e. the latter encapsulate the alpha'-expansion of the superstring amplitude. Moreover, a morphism induced by the coproduct maps the alpha'-expansion onto a non-commutative Hopf algebra. This map represents a generalization of the symbol of a transcendental function. In terms of elements of this Hopf algebra the alpha'-expansion assumes a very simple and symmetric form, which carries all the relevant information. Equipped with these results we can also cast the closed superstring amplitude into a very elegant form.

  9. Amplitude Variations in Pulsating Yellow Supergiants

    CERN Document Server

    Percy, John R

    2014-01-01

    It was recently discovered that the amplitudes of pulsating red giants and supergiants vary significantly on time scales of 20-30 pulsation periods. Here, we analyze the amplitude variability in 29 pulsating yellow supergiants (5 RVa, 4 RVb, 9 SRd, 7 long-period Cepheid, and 4 yellow hypergiant stars), using visual observations from the AAVSO International Database, and Fourier and wavelet analysis using the AAVSO's VSTAR package. We find that these stars vary in amplitude by factors of up to 10 or more (but more typically 3-5), on a mean time scale (L) of 33 +/- 4 pulsation periods (P). Each of the five sub-types shows this same behavior, which is very similar to that of the pulsating red giants, for which the median L/P was 31. For the RVb stars, the lengths of the cycles of amplitude variability are the same as the long secondary periods, to within the uncertainty of each.

  10. Transition amplitudes within the stochastic quantization scheme

    International Nuclear Information System (INIS)

    Quantum mechanical transition amplitudes are calculated within the stochastic quantization scheme for the free nonrelativistic particle, the harmonic oscillator and the nonrelativistic particle in a constant magnetic field; we close with free Grassmann quantum mechanics. (authors)

  11. [Role of ocular pulse amplitude in glaucoma].

    Science.gov (United States)

    Stürmer, J P E; Kniestedt, C

    2015-02-01

    The ocular pulse amplitude is defined as the difference between diastolic and systolic intraocular pressure. The ocular pulse is generated by the pulsatile ocular blood flow in the choroid. It is dependent on the dynamics of the cardiovascular system, the rigidity of the ocular vessels on one side and the biomechanical properties of the eye on the other side. In addition the influence of outflow facility of the aqueous humor, the level of the intraocular pressure itself and last but not least the rigidity of the sclera on the ocular pulse amplitude is until now not clear. Dynamic contour tonometry (Pascal®) does not only measure intraocular pressure almost independent of corneal thickness and curvature but also allows easy and fast measurement of ocular pulse amplitude on the slit lamp. The ocular pulse amplitude in healthy subjects is between 1.2 and 4?mmHg. If the ocular pulse amplitude is larger than 1.2?mmHg spontaneous pulsations of the central retinal vein are visible on fundoscopy. In patients with ocular hypertension the ocular pulse amplitude is larger than in normal subjects but this is mainly due to higher IOP levels. In patients with manifest open-angle glaucoma the ocular pulse amplitude stays initially within the normal range. In more advanced stages of the disease and especially in patients with ocular perfusion pressure dependent optic neuropathy the ocular pulse amplitude is gradually reduced. Due to the various factors influencing ocular pulse amplitude a direct correlation between reduced ocular pulse amplitude and reduced ocular perfusion pressure has not been established as yet. New approaches investigating the variations of the ocular pressure Fourier spectral analysis are promising, especially when simultaneous analysis of the arterial blood pressure is performed. These techniques may allow a fast and easy discrimination between healthy and glaucomatous patients in the near future. If ocular pulse amplitude exhibits a massive inter-ocular asymmetry in the presence of symmetrical ocular findings of extraocular vascular pathologies (i.e. carotid stenosis) are the most likely cause and therefore should be excluded. PMID:25700254

  12. Nucleon distribution amplitudes from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Kaltenbrunner, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (DE). John von Neumann-Inst. fuer Computing NIC] (and others)

    2008-04-15

    We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature. (orig.)

  13. Effective gluon interactions from superstring disk amplitudes

    International Nuclear Information System (INIS)

    In this thesis an efficient method for the calculation of the N-point tree-level string amplitudes is presented. Furthermore it is shown that the six-gluon open-superstring disk amplitude can be expressed by a basis of six triple hypergeometric functions, which encode the full ?' dependence. In this connection material for obtaining the ?' expansion of these functions is derived. Hereby many Euler-Zagier sums are calculated including multiple harmonic series. (HSI)

  14. Meson mixing amplitudes in asymmetric nuclear matter

    OpenAIRE

    Mori, Yoshiharu; Saito, Koichi

    2002-01-01

    Using a purely hadronic model, we study the charge-symmetry-breaking $\\rho$-$\\omega$, $\\sigma$-$\\delta$, $\\sigma$-$\\rho$ and $\\delta$-$\\omega$ mixing amplitudes in isospin asymmetric nuclear matter. The basic assumption of the model is that the mixing amplitude is generated by nucleon and anti-nucleon loops and hence driven entirely by the difference between proton and neutron Fermi momenta and the proton-neutron mass difference. We find that the behavior of the mixing ampli...

  15. Effective gluon interactions from superstring disk amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Oprisa, D.

    2006-05-15

    In this thesis an efficient method for the calculation of the N-point tree-level string amplitudes is presented. Furthermore it is shown that the six-gluon open-superstring disk amplitude can be expressed by a basis of six triple hypergeometric functions, which encode the full {alpha}' dependence. In this connection material for obtaining the {alpha}' expansion of these functions is derived. Hereby many Euler-Zagier sums are calculated including multiple harmonic series. (HSI)

  16. Path integral evaluation of Dbrane amplitudes

    OpenAIRE

    Chaudhuri, Shyamoli

    1999-01-01

    We extend Polchinski's evaluation of the measure for the one-loop closed string path integral to open string tree amplitudes with boundaries and crosscaps embedded in Dbranes. We explain how the nonabelian limit of near-coincident Dbranes emerges in the path integral formalism. We give a careful path integral derivation of the cylinder amplitude including the modulus dependence of the volume of the conformal Killing group.

  17. Subleading soft behavior of QCD amplitudes

    Science.gov (United States)

    Luo, Hui; Mastrolia, Pierpaolo; Torres Bobadilla, William J.

    2015-03-01

    We elaborate on the radiative behavior of tree-level scattering amplitudes in the soft regime. We show that the subleading soft term in single-gluon emission of quark-gluon amplitudes in QCD is controlled by differential operators, whose universal form can be derived from both on-shell recursion and gauge invariance, as it was shown to hold for graviton and gluon scattering.

  18. Topologically Modulated Signals and Predicate Gates For Their Processing

    CERN Document Server

    Kouzaev, G A

    2001-01-01

    In the paper electromagnetic signals distinguished by their discrete modulation of spatial distributions of fields and amplitudes are considered. Amplitudes of the impulses play a role of predicates and discrete spatial distributions of fields serve as predicate variables. Designed electronic gates are different by parallelism of the signal processing and allow to create a predicate processor for artificial intellect applications.

  19. Modulation masking produced by second-order modulators

    DEFF Research Database (Denmark)

    Füllgrabe, Christian; Moore, Brian C.J.

    2005-01-01

    Recent studies suggest that an auditory nonlinearity converts second-order sinusoidal amplitude modulation (SAM) (i.e., modulation of SAM depth) into a first-order SAM component, which contributes to the perception of second-order SAM. However, conversion may also occur in other ways such as cochlear filtering. The present experiments explored the source of the first-order SAM component by investigating the ability to detect a 5-Hz, first-order SAM probe in the presence of a second-order SAM masker beating at the probe frequency. Detection performance was measured as a function of masker-carrier modulation frequency, phase relationship between the probe and masker modulator, and probe modulation depth. In experiment 1, the carrier was a 5-kHz sinusoid presented either alone or within a notched-noise masker in order to restrict off-frequency listening. In experiment 2, the carrier was a white noise. The data obtained in both carrier conditions are consistent with the existence of a modulation distortion component. However, the phase yielding poorest detection performance varied across experimental conditions between 0° and 180°, confirming that, in addition to nonlinear mechanisms, cochlear filtering and off-frequency listening play a role in second-order SAM perception. The estimated magnitude of the modulation distortion component ranges from 5%–12%. ©2005 Acoustical Society of America.

  20. The piNNN--NNN problem. Connectedness, transition amplitudes and quasi-particle approximation

    OpenAIRE

    Cattapan, Giorgio; Canton, Luciano

    1997-01-01

    In this paper we review the present status of the piNNN--NNN problem. In particular, we re-consider the chain-labelled approach recently proposed by us, and identify a class of graphs, previously overlooked, which prevents the kernel of the corresponding piNNN--NNN equations from being connected. We propose some pproximate schemes, yielding connected-kernel equations. A generalization of the residue method allows to relate the transition amplitudes for the coupled piNNN--NNN...

  1. Intrinsic-normal-ordered vertex operators from the multiloop N-tachyon amplitude

    International Nuclear Information System (INIS)

    We construct vertex operators for arbitrary mass level states of the closed bosonic string. Starting from a generalization of the Koba-Nielsen amplitude which is suitable for an arbitrary genus Riemann surface, we read the vertex operators from the residues of the poles for the intermediate states. Since the original expression is metric independent and normal ordered without the need of inventing any regularization scheme, our vertex operators also possess these properties. We discuss their general features. (author). 17 refs

  2. Frequency Modulation of Spin-Transfer Oscillators

    CERN Document Server

    Pufall, M R; Kaka, S; Silva, T J; Russek, S E

    2004-01-01

    Spin-polarized dc electric current flowing into a magnetic layer can induce precession of the magnetization at a frequency that depends on current. We show that addition of an ac current to this dc bias current results in a frequency modulated (FM) spectral output, generating sidebands spaced at the modulation frequency. The sideband amplitudes and shift of the center frequency with drive amplitude are in good agreement with a nonlinear FM model that takes into account the nonlinear frequency-current relation generally induced by spin transfer. Single-domain simulations show that ac current modulates the cone angle of the magnetization precession, in turn modulating the frequency via the demagnetizing field. These results are promising for communications and signal processing applications of spin-transfer oscillators.

  3. Modulational development of nonlinear gravity-wave groups

    Science.gov (United States)

    Chereskin, T. K.; Mollo-Christensen, E.

    1985-01-01

    Observations of the development of nonlinear surface gravity-wave groups are presented, and the amplitude and phase modulations are calculated using Hilbert-transform techniques. With increasing propagation distance and wave steepness, the phase modulation develops local phase reversals whose locations correspond to amplitude minima or nodes. The concomitant frequency modulation develops jumps or discontinuities. The observations are compared with recent similar results for wavetrains. The observations are modelled numerically using the cubic nonlinear Schroedinger equation. The motivation is twofold: to examine quantitatively the evolution of phase as well as amplitude modulation, and to test the inviscid predictions for the asymptotic behavior of groups versus long-time observations. Although dissipation rules out the recurrence, there is a long-time coherence of the groups. The phase modulation is found to distinguish between dispersive and soliton behavior.

  4. Wave amplitude variation and energy flow in autoresonant collective ion acceleration

    International Nuclear Information System (INIS)

    An expression for the energy of small-amplitude waves in a radially inhomogeneous cold-fluid unneutralized relativistic electron beam is obtained in terms of the wave amplitudes. The result is employed together with conservation of wave energy to determine how the axial electric field strength and beam-edge modulation associated with slow cyclotron waves change with position in an electron beam propagating along the adiabatically spatially decreasing magnetic guide field of an autoresonant collective ion accelerator. The resulting axial profiles are found to depart markedly from those of earlier radially homogeneous beam calculations. Possible impacts of these findings on a planned autoresonant acceleration feasibility experiment are discussed

  5. Wood residues in Alberta

    International Nuclear Information System (INIS)

    The forest products industry is the third largest economic sector in Alberta, producing pulp and paper, dimensional lumber, paneling, and value added products, providing some 40,000 jobs . 'Value added' is a key component of expanding economic activity within the forest products sector. Wood residues can play a key role in obtaining more value from forest resources by providing new products, serving as feedstock to energy and chemical production, and playing a role in agriculture and land reclamation. One of the principal roles of the Forest Products Development Branch of the Alberta Economics Department is to encourage the development of the industry by creating new uses for these materials and developing awareness of the scope of the resource. Distances to markets, economic competition from conventional energy sources and coordination of research efforts are substantial barriers to further development that the Forest Products Development Branch has to face daily. Some notable successes in recent years are described. These include the Wood Residue Inventory and the Wood Residue Database that provide data on availability and principal location of wood residues, also a listing of contacts at the mills who produce the materials

  6. Phase and amplitude measurements for high bandwidth optical signals

    Science.gov (United States)

    Bulus Rossini, Laureano A.; Costanzo Caso, Pablo A.; Paulucci, Emanuel; Duchowicz, Ricardo; Sicre, Enrique E.

    2014-08-01

    In this paper a novel technique for obtaining the amplitude and phase of optical pulses with time extents as short as tens of ps is presented. The method which is based on the transport-of-intensity equation only requires, for a practical realization, of passive fiber optic devices. It employs as the main component a dispersive element with a known second order dispersion coefficient. Two different setup implementations are considered, for which simulations are carried out in order to test the method performance taking into account both, realizable models of the involved devices and typical pulses found in optical transmission systems. The characterization of optical pulses affected by dispersion and nonlinear effects, such as self-phase modulation, is used to evaluate the performance of the method and show the practical feasibility of the future implementation.

  7. Improved RF Phase and Amplitude Detection for ICRF Heating Experiments

    Science.gov (United States)

    Sanchez, A.; Pinsker, R. I.; Baity, F. W.; Eguizabal, A.; Fredd, E.; Greenough, N.; Nagy, A.

    2010-11-01

    For diagnosis and control of high-power rf heating systems, it is necessary to measure the rf amplitude and phase of signals at multiple points in the rf transmission lines. We are upgrading the signal processing modules used in the fast-wave system on the DIII-D tokamak to improve reliability and temporal resolution. The goal is to enable resolution of phenomena on microsecond timescales for studies of antenna arcing and ELMs. This work compares several possible approaches to this upgrade, including ICs that contain most of the functionality of the original designs on a single chip, schemes involving digitizing the rf in bursts, and updates of the existing systems. The techniques are compared in the achievable time resolution, accuracy, precision, dynamic range and unit cost.

  8. Displaced phase-amplitude variables for waves on finite background

    International Nuclear Information System (INIS)

    Wave amplification in nonlinear dispersive wave equations may be caused by nonlinear focussing of waves from a certain background. In the model of nonlinear Schroedinger equation we will introduce a transformation to displaced phase-amplitude variables with respect to a background of monochromatic waves. The potential energy in the Hamiltonian then depends essentially on the phase. Looking as a special case to phases that are time independent, the oscillator equation for the signal at each position becomes autonomous, with the change of phase with position as only driving force for a spatial evolution towards extreme waves. This is observed to be the governing process of wave amplification in classes of already known solutions of NLS, namely the Akhmediev-, Ma- and Peregrine-solitons. We investigate the case of the soliton on finite background in detail in this Letter as the solution that describes the complete spatial evolution of modulational instability from background to extreme waves

  9. Filamentation instability of large-amplitude Alfven waves

    Science.gov (United States)

    Kuo, S. P.; Whang, M. H.; Lee, M. C.

    1988-01-01

    An instability that leads to the filamentation of large-amplitude Alfven waves and gives rise to purely growing density and magnetic field fluctuations is studied. The dispersion relation of the instability is derived, from which the threshold conditions and the growth rates of the instability are analyzed quantitatively for applications to the solar wind plasma. Their dependence on the filamentation spectrum, the plasma beta, and the pump frequency and intensity was examined for both right-hand and left-hand circularly polarized Alfven waves. The excitation of filamentation instability for certain cases of interest is discussed and compared with that of the parametric decay and modulation instability. The relevance of the proposed instability to some observations is discussed.

  10. Amplitude and phase-locking adaptation of neural oscillation in the rat auditory cortex in response to tone sequence.

    Science.gov (United States)

    Noda, Takahiro; Kanzaki, Ryohei; Takahashi, Hirokazu

    2014-02-01

    Sensory adaptation allows stimulus sensitivity to be dynamically modulated according to stimulus statistics and plays pivotal roles in efficient neural computation. Here, it is hypothesized that in the auditory cortex, phase locking of local field potentials (LFPs) to test tones exhibits an adaptation property, i.e., phase-locking adaptation, which is distinct from the amplitude adaptation of oscillatory components. Series of alternating tone sequences were applied in which the inter-tone interval (ITI) and frequency difference (?F) between successive tones were varied. Then, adaptation was characterized by the temporal evolution of the band-specific amplitude and phase locking evoked by the test tones. Differences as well as similarities were revealed between amplitude and phase-locking adaptations. First, both amplitude and phase-locking adaptations were enhanced by short ITIs and small ?Fs. Second, the amplitude adaptation was more effective in a higher frequency band, while the phase-locking adaptation was more effective in a lower frequency band. Third, as with the adaptation of multiunit activities (MUAs), the amplitude adaptation occurred mainly within a second, while the phase-locking showed multi-second adaptation specifically in the gamma band for short ITI and small ?F conditions. Fourth, the amplitude adaptation and phase-locking adaptation were co-modulated in a within-second time scale, while this co-modulation was not observed in a multi-second time scale. These findings suggest that the amplitude and phase-locking adaptations have different mechanisms and functions. The phase-locking adaptation is likely to play more crucial roles in encoding a temporal structure of stimulus than the amplitude adaptation. PMID:24239971

  11. Modulation instability of spiral density waves

    International Nuclear Information System (INIS)

    The modulation instability of tightly wrapped spiral density waves in a differentially rotating flat subsystem of a galaxy is considered. The nonlinear equation determining the evolution of the amplitude of spiral density waves is obtained. For the typical parameters of spiral pattern instability occurs if the space scale of modulation is larger than the critical one. The time scale of instability is less or equal to the time of one complete revolution of the system

  12. Electronic structure of magnetically modulated graphene

    OpenAIRE

    Sabeeh, K.; Tahir, M.; Mackinnon, A.

    2008-01-01

    We present a theoretical study of the electronic structure of magnetically modulated graphene. We consider monolayer graphene in the presence of a perpendicular magnetic field and a unidirectional weak magnetic modulation. The density of states and the bandwidth of the Dirac electrons in this system are determined. We have found magnetic Weiss oscillations in the bandwidth and the density of states. These oscillations are out of phase and larger in amplitude than the ones in...

  13. Scattering amplitudes in open superstring theory

    International Nuclear Information System (INIS)

    The present thesis deals with the theme field of the scattering amplitudes in theories of open superstrings. Especially two different formalisms for the handling of superstrings are introduced and applied for the calaculation of tree-level amplitudes - the Ramond- Neveu-Schwarz (RNS) and the Pure-Spinor (PS) formalism. The RNS approach is proved as flexible in order to describe compactification of the initially ten flat space-time dimensions to four dimensions. We solve the technical problems, which result from the interacting basing world-sheet theory with conformal symmetry. This is used to calculate phenomenologically relevant scattering amplitudes of gluons and quarks as well as production rates of massive harmonic vibrations, which were already identified as virtual exchange particles on the massless level. In the case of a low string mass scale in the range of some Tev the string-specific signatures in parton collisions can be observed in the near future in the LHC experiment at CERN and indicated as first experimental proof of the string theory. THose string effects occur universally for a wide class of string ground states respectively internal geometries and represent an elegant way to avoid the so-called landscape problem of the string theory. A further theme complex in this thesis is based on the PS formalism, which allows a manifestly supersymmetric treatment of scattering amplitudes in ten space-time dimension with sixteen supercharges. We introduce a family of superfields, which occur in massless amplitudes of the open string and can be naturally identified with diagrams of three-valued knots. Thereby we reach not only a compact superspace representation of the n-point field-theory amplitude but can also write the complete superstring n-point amplitude as minimal linear combination of partial amplitudes of the field theory as well as hypergeometric functions. The latter carry the string effects and are analyzed from different perspectives, above all with regards to the duality between group-theoretical and kinematic contributions to tree-level amplitudes observed in the field theory.

  14. Scattering amplitudes in open superstring theory

    Energy Technology Data Exchange (ETDEWEB)

    Schlotterer, Oliver

    2011-07-15

    The present thesis deals with the theme field of the scattering amplitudes in theories of open superstrings. Especially two different formalisms for the handling of superstrings are introduced and applied for the calaculation of tree-level amplitudes - the Ramond- Neveu-Schwarz (RNS) and the Pure-Spinor (PS) formalism. The RNS approach is proved as flexible in order to describe compactification of the initially ten flat space-time dimensions to four dimensions. We solve the technical problems, which result from the interacting basing world-sheet theory with conformal symmetry. This is used to calculate phenomenologically relevant scattering amplitudes of gluons and quarks as well as production rates of massive harmonic vibrations, which were already identified as virtual exchange particles on the massless level. In the case of a low string mass scale in the range of some Tev the string-specific signatures in parton collisions can be observed in the near future in the LHC experiment at CERN and indicated as first experimental proof of the string theory. THose string effects occur universally for a wide class of string ground states respectively internal geometries and represent an elegant way to avoid the so-called landscape problem of the string theory. A further theme complex in this thesis is based on the PS formalism, which allows a manifestly supersymmetric treatment of scattering amplitudes in ten space-time dimension with sixteen supercharges. We introduce a family of superfields, which occur in massless amplitudes of the open string and can be naturally identified with diagrams of three-valued knots. Thereby we reach not only a compact superspace representation of the n-point field-theory amplitude but can also write the complete superstring n-point amplitude as minimal linear combination of partial amplitudes of the field theory as well as hypergeometric functions. The latter carry the string effects and are analyzed from different perspectives, above all with regards to the duality between group-theoretical and kinematic contributions to tree-level amplitudes observed in the field theory.

  15. Attenuation of ground-motion spectral amplitudes in southeastern Australia

    Science.gov (United States)

    Allen, T.I.; Cummins, P.R.; Dhu, T.; Schneider, J.F.

    2007-01-01

    A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for southeastern Australia (SEA). Events were recorded from 1993 to 2004 and range in size from moment magnitude 2.0 ??? M ??? 4.7. The decay of vertical-component Fourier spectral amplitudes is modeled by trilinear geometrical spreading. The decay of low-frequency spectral amplitudes can be approximated by the coefficient of R-1.3 (where R is hypocentral distance) within 90 km of the seismic source. From approximately 90 to 160 km, we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and Moho discontinuities. In this hypocentral distance range, geometrical spreading is approximately R+0.1. Beyond 160 km, low-frequency seismic energy attenuates rapidly with source-receiver distance, having a geometrical spreading coefficient of R-1.6. The associated regional seismic-quality factor can be expressed by the polynomial: log Q(f) = 3.66 - 1.44 log f + 0.768 (log f)2 + 0.058 (log f)3 for frequencies 0.78 ??? f ??? 19.9 Hz. Fourier spectral amplitudes, corrected for geometrical spreading and anelastic attenuation, are regressed with M to obtain quadratic source scaling coefficients. Modeled vertical-component displacement spectra fit the observed data well. Amplitude residuals are, on average, relatively small and do not vary with hypocentral distance. Predicted source spectra (i.e., at R = 1 km) are consistent with eastern North American (ENA) Models at low frequencies (f less than approximately 2 Hz) indicating that moment magnitudes calculated for SEA earthquakes are consistent with moment magnitude scales used in ENA over the observed magnitude range. The models presented represent the first spectral ground-motion prediction equations develooed for the southeastern Australian region. This work provides a useful framework for the development of regional ground-motion relations for earthquake hazard and risk assessment in SEA.

  16. Amplitude scaling of asymmetry-induced transport

    International Nuclear Information System (INIS)

    Our initial experiments on asymmetry-induced transport in non-neutral plasmas found the radial particle flux at small radii to be proportional to ?a2, where ?a is the applied asymmetry amplitude. Other researchers, however, using the global expansion rate as a measure of the transport, have observed a ?a1 scaling when the rigidity (the ratio of the axial bounce frequency to the azimuthal rotation frequency) is in the range one to ten. In an effort to resolve this discrepancy, we have extended our measurements to different radii and asymmetry frequencies. Although the results to date are generally in agreement with those previously reported (?a2 scaling at low asymmetry amplitudes falling off to a weaker scaling at higher amplitudes), we have observed some cases where the low amplitude scaling is closer to ?a1. Both the ?a2 and ?a1 cases, however, have rigidities less than ten. Instead, we find that the ?a1 cases are characterized by an induced flux that is comparable in magnitude but opposite in sign to the background flux. This suggests that the mixing of applied and background asymmetries plays an important role in determining the amplitude scaling of this transport

  17. Exchange process amplitudes in coherent pion production

    International Nuclear Information System (INIS)

    Calculations have been done that assess the importance of projectile-generated and target-generated pions for the exclusive reaction 12C+12C?12C(15.11 MeV)+12C+?0 below and near threshold. Both the amplitude for ? formation in the target with subsequent decay to ?0's while simultaneously exciting the projectile to the M1 giant resonant state at 15.11 MeV, and the exchange process amplitude, in which the target and projectile exchange roles, are included in the calculations for the pion triple differential cross sections. For the first time, results of the pion energy and pion angular and ejectile angular distributions are shown with both amplitudes properly included. Also for the first time in this work, pion and ejectile distributions are shown in the laboratory frame after the appropriate relativistic transformations are performed. The projectile-generated pion amplitude is the major contributor to the pion energy and ejectile angular distribution; whereas, both amplitudes are equally important in the pion angular distribution and give rise to a unique signature for coherent pion production as seen in the c.m. frame

  18. Residual charge of niobium spheres

    International Nuclear Information System (INIS)

    In 1964, Gell-Mann and Zweig hypothesized that the particles inside nuclei are composed of quarks with electric charges of ± 1/3 e and ± 1/2 e. Since then, many searches have been made for stable fractional charges. The experiment described in a Millikan-type electrometer with a sample 107 times heavier. A 0.28 mm diameter superconducting niobium ball is levitated magnetically between capacitor plates. The ball oscillates vertically on this magnetic spring and an electric field is applied at the oscillation frequency. The rate of change of the ball's oscillation amplitude is proportional to the force exerted on the ball by the electric field. The force on the ball is measured as a function of its position between the capacitor plates to discriminate against the background force due to the patch effect field gradient of the plates. There is one other background effect, due to the tilting of the ball's magnetic moment, which has sometimes manifested itself as a drift or occasionally as an offset in the measured force. An analysis presented in this thesis explains a mechanism for this effect and shows that we can eliminate it in our next run by spinning the ball about the vertical axis. The results are strong evidence for the existence of stable fractional charges of ± 1/3 e in matter. Out of 58 measurements on 20 balls, 9 have yielded results near - 1/3 e, 34 near 0, 13 near + 1/3e, one of the 0.19 e, and one of 0.44 e. Out of 38 repeat measurements, theree. Out of 38 repeat measurements, there have been 12 residual charge changes, 5 near - 1/3e and 7 near + 1/3 e

  19. Digital front-end module (DFEM) series; Digital front end module (DFEM) series

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    The digital front-end module (DFEM) is a module in which the processes ranging from the reception of digitally modulated radiofrequencies to the output of digital IF (Intermediate Frequency) signals or data streams are integrated. Beginning with a module for the MCNS (Multimedia Cable Network System) cable modem which was the first module in this business field approved by the Cable Labs, U.S., Toshiba has developed a series of DFEMs for various digital media for satellites, ground waves, and CATV (Cable Television) systems. The series is characterized by (1) the serialization of DFEMs compatible with various digital modulation techniques such as 8 PSK (Phase Shift Keying), OFDM (Orthogonal Frequency Division Multiplexing), and 256 QAM (Quadrature Amplitude Modulation), (2) easy connection with digital circuits thanks to the high shielding effect, and (3) the achievement of smaller size, higher performance, and lower power consumption. (translated by NEDO)

  20. Observability of hexagons in modulated Rayleigh--Benard convection

    International Nuclear Information System (INIS)

    The prediction of Roppo, Davis, and Rosenblat [Phys. Fluids 27, 796 (1984)] that hexagons should appear near threshold in a Rayleigh--Benard cell under external modulation of the temperature is reconsidered with a view to determining the experimental observability of the effect. It is found that in the limit of low-modulation amplitude ? considered by Roppo et al. the effects are qualitatively as given by these authors, but considerably smaller quantitatively. The validity limits of the small-? expansion are clarified and results of an alternative theory of hexagonal effects, valid at arbitrary amplitude ? and frequency ?, are briefly summarized. Hexagons will only be observable if large amplitudes can be achieved

  1. Modulation enhancement in the electrical signal improves perception of interaural time differences with bimodal stimulation.

    Science.gov (United States)

    Francart, Tom; Lenssen, Anneke; Wouters, Jan

    2014-08-01

    Interaural timing cues are important for sound source localization and for binaural unmasking of speech that is spatially separated from interfering sounds. Users of a cochlear implant (CI) with residual hearing in the non-implanted ear (bimodal listeners) can only make very limited use of interaural timing cues with their clinical devices. Previous studies showed that bimodal listeners can be sensitive to interaural time differences (ITDs) for simple single- and three-channel stimuli. The modulation enhancement strategy (MEnS) was developed to improve the ITD perception of bimodal listeners. It enhances temporal modulations on all stimulated electrodes, synchronously with modulations in the acoustic signal presented to the non-implanted ear, based on measurement of the amplitude peaks occurring at the rate of the fundamental frequency in voiced phonemes. In the first experiment, ITD detection thresholds were measured using the method of constant stimuli for five bimodal listeners for an artificial vowel, processed with either the advanced combination encoder (ACE) strategy or with MEnS. With MEnS, detection thresholds were significantly lower, and for four subjects well within the physically relevant range. In the second experiment, the extent of lateralization was measured in three subjects with both strategies, and ITD sensitivity was determined using an adaptive procedure. All subjects could lateralize sounds based on ITD and sensitivity was significantly better with MEnS than with ACE. The current results indicate that ITD cues can be provided to bimodal listeners with modified sound processing. PMID:24890714

  2. Automatic prediction of catalytic residues by modeling residue structural neighborhood

    OpenAIRE

    Passerini Andrea; Cilia Elisa

    2010-01-01

    Abstract Background Prediction of catalytic residues is a major step in characterizing the function of enzymes. In its simpler formulation, the problem can be cast into a binary classification task at the residue level, by predicting whether the residue is directly involved in the catalytic process. The task is quite hard also when structural information is available, due to the rather wide range of roles a functional residue can play and to the large imbalance between the number of catalytic...

  3. Modulated ECCD experiments on TCV

    International Nuclear Information System (INIS)

    Experiments were previously performed on TCV using Switched Electron Cyclotron Current Drive (SECCD) in which the total heating power and plasma current were kept nearly constant in time while the current density profile was modulated. It was observed that SECCD leads to relative electron diffusivity modulation amplitude of ±65%. A direct measurement of the current density profile is not available on TCV; however, electrodynamics calculations show that ±55% shear modulation (from s = 0.20 to 0.70) is achieved during SECCD experiments, and that the shear modulation is localized at the CD layer position. These results provide strong experimental evidence that electron heat transport is shearing dependent: heat transport is reduced when shear is low, confirming a general observation. New experiments have been performed to address some open issues raised after the previous campaign. The work is also aimed at confirmation of the electrodynamics model of the SECCD technique. To these ends, the experiments have been performed at different deposition radii, different SECCD amplitudes and different toroidal injection angles. It turned out that in most discharges an MHD activity develops, differentiated in the co and counter injection phases, which prevents an unambiguous conclusion in terms of heat or particle transport. It is shown that the MHD modes are affected by ECCD on the resonant magnetic surfaces, possibly according to the same physics underlying TM and NTM stabilize physics underlying TM and NTM stabilization process. Data analysis from this point of view is in progress. (author)

  4. Novel modulation techniques for collinear holographic data encoding

    Science.gov (United States)

    Jia, Wei; Chen, Zhongyu; Chung, Tsing; Wen, Fung Jacky; Chow, Yuk Tak; Chung, Po Sheun

    2012-03-01

    We describe two novel modulation techniques for collinear holographic data encoding, employing a spatial light modulator (SLM) based on twisted nematic LCD. In the Fourier transform holographic storage system, the reference beam in the outside part and the object beam in the inside part are simultaneously modulated by one single SLM, with different modulation techniques. In one of the modulation methods, the reference beam is phase modulated with a circular blazed grating pattern, and then diffracted into the central part to interfere with the amplitude modulated object beam. Multiple holograms can be recorded on the same location with reference beams of different grating period. Another modulation method is to modulate both the reference beam and the object beam with pure phase modulation by the SLM. The binary ones are encoded with random phase shift from 0 to 2?, while the binary zeroes are encoded with a constant phase of 0. When the dc component of the spatial frequency generated by the binary zeroes is blocked, a homogeneous hologram will be obtained, and the amplitude object will be reconstructed directly. In this paper, both of the two modulation methods are performed theoretically and experimentally. From the experimental results, it can be seen that the blazed-grating modulation technique gets a higher efficiency, while pure phase modulation method can reconstruct the images with more uniform intensity. These techniques are demonstrated to be attractive for applications in data storage and encryption systems.

  5. Scaling of saturation amplitudes in baroclinic instability

    International Nuclear Information System (INIS)

    By using finite-amplitude conservation laws for pseudomomentum and pseudoenergy, rigorous upper bounds have been derived on the saturation amplitudes in baroclinic instability for layered and continuously-stratified quasi-geostrophic models. Bounds have been obtained for both the eddy energy and the eddy potential enstrophy. The bounds apply to conservative (inviscid, unforced) flow, as well as to forced-dissipative flow when the dissipation is proportional to the potential vorticity. This approach provides an efficient way of extracting an analytical estimate of the dynamical scalings of the saturation amplitudes in terms of crucial non-dimensional parameters. A possible use is in constructing eddy parameterization schemes for zonally-averaged climate models. The scaling dependences are summarized, and compared with those derived from weakly-nonlinear theory and from baroclinic-adjustment estimates

  6. Residual Component Analysis

    OpenAIRE

    Kalaitzis, Alfredo A.; Lawrence, Neil D.

    2011-01-01

    Probabilistic principal component analysis (PPCA) seeks a low dimensional representation of a data set in the presence of independent spherical Gaussian noise, Sigma = (sigma^2)*I. The maximum likelihood solution for the model is an eigenvalue problem on the sample covariance matrix. In this paper we consider the situation where the data variance is already partially explained by other factors, e.g. covariates of interest, or temporal correlations leaving some residual varia...

  7. The geometry of one-loop amplitudes

    CERN Document Server

    Schnetz, Oliver

    2010-01-01

    We review a reduction formula by Petersson that reduces the calculation of a one-loop amplitude with N external lines in namplitude is shown to be equivalent to the calculation of the volume of a tetrahedron spanned by the momenta in (n-1)-dimensional hyperbolic space. The underlying geometry is intimately linked to the geometry of the reduction formula.

  8. Amplitude and phase in quantum optics

    International Nuclear Information System (INIS)

    A quantum description of light - what else could be meant than that light consists of photons? What could be more apparent than that a quantum description requires one to think in terms of photons? Nonetheless, in this paper, the author asks the reader to set aside the notion of photons and to think of light in nearly classical terms. A beam of light is viewed as an electromagnetic field with a nearly sinusoidal time dependence. The time dependence is characterized by a mean amplitude and a mean phase, on which are superposed fluctuations in amplitude and phase-fluctuations which when reduced to a minimum are quantum in origin

  9. Singularity structure of maximally supersymmetric scattering amplitudes.

    Science.gov (United States)

    Arkani-Hamed, Nima; Bourjaily, Jacob L; Cachazo, Freddy; Trnka, Jaroslav

    2014-12-31

    We present evidence that loop amplitudes in maximally supersymmetric (N=4) Yang-Mills theory (SYM) beyond the planar limit share some of the remarkable structures of the planar theory. In particular, we show that through two loops, the four-particle amplitude in full N=4 SYM has only logarithmic singularities and is free of any poles at infinity--properties closely related to uniform transcendentality and the UV finiteness of the theory. We also briefly comment on implications for maximal (N=8) supergravity theory (SUGRA). PMID:25615304

  10. Gluon scattering amplitudes at strong coupling

    CERN Document Server

    Alday, Luis F

    2007-01-01

    We describe how to compute planar gluon scattering amplitudes at strong coupling in N=4 super Yang Mills by using the gauge/string duality. The computation boils down to finding a certain classical string configuration whose boundary conditions are determined by the gluon momenta. The results are infrared divergent. We introduce the gravity version of dimensional regularization to define finite quantities. The leading and subleading IR divergencies are characterized by two functions of the coupling that we compute at strong coupling. We compute also the full finite form for the four point amplitude and we find agreement with a recent ansatz by Bern, Dixon and Smirnov.

  11. Transition amplitude for free massless particle

    International Nuclear Information System (INIS)

    The propagator for massless particle of arbitrary spin is represented as BFV-BRST path integral in index spinor formalism. The classical formulation of the theory is investigated and it is carried out its Hamiltonization procedure. The structure functions are obtained. The BRST-charge of the model is calculated and it is shown, that it has the first rank. The expression for transition amplitude is transformed to the form of amplitude for a system with only the first class constraints. it is shown, that complexification of some phase variable results in the Gupta-Bleuler formalism. In these frameworks it is considered quantization procedure

  12. Experimental measurement of resonance islands induced by rf voltage modulation

    International Nuclear Information System (INIS)

    Synchrotron motion with an external rf voltage modulation was studied experimentally. Beam particles, in the presence of electron cooling, were observed to damp to the basins of resonance islands, which were produced by the parametric resonance due to rf voltage modulation. The measured phase amplitudes of the centers of these resonance islands were found to agree well with theory

  13. Analysis of Peak-to-Peak Current Ripple Amplitude in Seven-Phase PWM Voltage Source Inverters

    OpenAIRE

    Gabriele Grandi; Jelena Loncarski

    2013-01-01

    Multiphase systems are nowadays considered for various industrial applications. Numerous pulse width modulation (PWM) schemes for multiphase voltage source inverters with sinusoidal outputs have been developed, but no detailed analysis of the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been reported. Determination of current ripple in multiphase PWM voltage source inverters is important for both design and control purposes. This paper gives the c...

  14. Use of the delta-t method for setting rf phase and amplitude for the AHF linac

    International Nuclear Information System (INIS)

    The delta-t procedure is a time-of-flight method of finding set points for the rf phase and amplitude for each module of a linac. Expected errors for LAMPF afterburner linacs which might be used for an advanced hadron facility (AHF) are calculated. The modified delta-t procedure used on modules 13 through 48 of the present linac appears adequate to set up the proposed AHF linacs. 24 refs., 7 figs., 1 tab

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

    Science.gov (United States)

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

    2009-06-01

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

  16. The use of TWT amplifiers in M-ary amplitude and phase shift keying systems

    Science.gov (United States)

    Weber, W. J., III

    1975-01-01

    A great deal of research is presently being conducted to study modulation schemes in order to reduce the bandwidth of digital communications. These M-ary amplitude and phase shift keying (MAPSK) modulation systems place new requirements on TWT amplifiers in space applications in that the various signal sets usually include two or more discrete output power levels as well as discrete phases at each power level. This paper presents a variety of predistortion schemes to circumvent the TWT problems of AM distortion and AM-to-PM conversion in order to produce MAPSK signal sets. A feedback scheme is presented to correct for long-term phase and amplitude drifts in the transmitter. A complete transmitter is proposed using predistortion to produce the desired MAPSK signal set at very high data rates including the possible use of a feedback stabilization scheme.

  17. Simulation study of the interaction between large-amplitude HF radio waves and the ionosphere

    CERN Document Server

    Eliasson, B; Eliasson, Bengt; Thid\\'e, Bo

    2006-01-01

    The time evolution of a large-amplitude electromagnetic (EM) wave injected vertically into the overhead ionosphere is studied numerically. The EM wave has a carrier frequency of 5 MHz and is modulated as a Gaussian pulse with a width of ca 0.1 milliseconds and a vacuum amplitude of 1.5 V/m. The pulse is propagated through the neutral atmosphere to the critical points of the magnetosphere where the ordinary (O) and extraordinary (X) modes are reflected, and back to the neutral atmosphere. We observe mode conversion of the O mode to electrostatic waves, as well as harmonic generation at the turning points of both the X and O modes, where their amplitudes rise to several times the original ones. The study has relevance for ionospheric interaction experiments in combination with ground-based and satellite or rocket observations.

  18. Modulational instability for nonlinear Schrodinger equations with a periodic potential

    CERN Document Server

    Bronski, J C; Bronski, Jared C.; Rapti, Zoi

    2005-01-01

    We study the stability properties of periodic solutions to the Nonlinear Schr\\"odinger (NLS) equation with a periodic potential. We exploit the symmetries of the problem, in particular the Hamiltonian structure and the $\\U(1)$ symmetry. We develop a simple sufficient criterion that guarantees the existence of a modulational instability spectrum along the imaginary axis. In the case of small amplitude solutions that bifurcate from the band edges of the linear problem this criterion becomes especially simple. We find that the small amplitude solutions corresponding to the band edges alternate stability, with the first band edge being modulationally unstable in the focusing case, the second band edge being modulationally unstable in the defocusing case, and so on. This small amplitude result has a nice physical interpretation in terms of the effective mass of a particle in the periodic potential. We also consider, in somewhat less detail, some sideband instabilities in the small amplitude limit. We find that, de...

  19. Electro-mechanically induced GHz rate optical frequency modulation in silicon

    CERN Document Server

    Tallur, Siddharth

    2012-01-01

    We present a monolithic silicon acousto-optic frequency modulator (AOFM) operating at 1.09GHz. Direct spectroscopy of the modulated laser power shows asymmetric sidebands which indicate coincident amplitude modulation and frequency modulation. Employing mechanical levers to enhance displacement of the optical resonator resulted in greater than 67X improvement in the opto-mechanical frequency modulation factor over earlier reported numbers for silicon nanobeams.

  20. Time Reversal UWB Communication System: A Novel Modulation Scheme with Experimental Validation

    OpenAIRE

    Khaleghi A; El Zein G; Ih, Naqvi

    2010-01-01

    A new modulation scheme is proposed for a time reversal (TR) ultra wide-band (UWB) communication system. The new modulation scheme uses the binary pulse amplitude modulation (BPAM) and adds a new level of modulation to increase the data rate of a TR UWB communication system. Multiple data bits can be transmitted simultaneously with a cost of little added interference. Bit error rate (BER) performance and the maximum achievable data rate of the new modulation scheme are theoretically analyzed...

  1. Simultaneous Amplitude and Phase Measurement for Periodic Optical Signals Using Time-Resolved Optical Filtering

    OpenAIRE

    Ho, Keangpo; Wang, Hsi-cheng; Chen, Hau-kai; Wu, Cheng-chen

    2005-01-01

    Time-resolved optical filtering (TROF) measures the spectrogram or sonogram by a fast photodiode followed a tunable narrowband optical filter. For periodic signal and to match the sonogram, numerical TROF algorithm is used to find the original complex electric field or equivalently both the amplitude and phase. For phase-modulated optical signals, the TROF algorithm is initiated using the craters and ridges of the sonogram.

  2. Children discover the spectral skeletons in their native language before the amplitude envelopes

    OpenAIRE

    Nittrouer, Susan; Lowenstein, Joanna H.; Packer, Robert

    2009-01-01

    Much of speech perception research has focused on brief spectro-temporal properties in the signal, but some studies have shown that adults can recover linguistic form when those properties are absent. In this experiment, seven-year-old English-speaking children demonstrated adult-like abilities to understand speech when only sine waves replicating the three lowest resonances of the vocal tract were presented, but failed to demonstrate comparable abilities when noise bands amplitude-modulated ...

  3. Machine for compacting solid residues

    International Nuclear Information System (INIS)

    Machine for compacting solid residues, particularly bulky radioactive residues, constituted of a horizontally actuated punch and a fixed compression anvil, in which the residues are first compacted horizontally and then vertically. Its salient characteristic is that the punch and the compression anvil have embossments on the compression side and interpenetrating plates in the compression position

  4. Lifetime and residual strength of materials

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1997-01-01

    The DVM-theory (Damaged Viscoelastic Material) previously developed by the author to predict lifetime of wood subjected to static loads is further developed in this paper such that harmonic load variations can also be considered. Lifetime (real time or number of cycles) is predicted as a function of load amplitude, load average, fractional time under maximum load, and load frequency.The analysis includes prediction of residual strength (re-cycle strength) during the process of load cycling. It is concluded that number of cycles to failure is a very poor design criterion. It is demonstrated how the theory developed can be generalized also to consider non-harmonic load variations.Algorithms are presented for design purposes which may be suggested as qualified alternatives to the Palmgren-Miner's methods normally used in fatigue analysis of materials under arbitrary load variations. Prediction by Palmgren-Miner methods may cause considerably overestimated time to failure of viscoelastic materials, especially at low frequencies.

  5. Particle Distribution Modification by Low Amplitude Modes

    Energy Technology Data Exchange (ETDEWEB)

    R.B. White, N. Gorelenkov, W.W. Heidbrink, and M.A. Van Zeeland

    2009-08-28

    Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

  6. Elastic amplitudes and power corrections in QCD

    International Nuclear Information System (INIS)

    We discuss two power-suppressed quantities in hadronic scattering: elastic amplitudes at fixed angles, and power corrections to inclusive hadronic cross sections. Generalized factorization theorems allow us to determine the asymptotic behavior of elastic scattering, and to relate 1/Q2 corrections in deeply inelastic scattering and the Drell-Yan process. 13 refs

  7. Constraints on low energy Compton scattering amplitudes

    International Nuclear Information System (INIS)

    We derive the constraints and correlations of fairly general type for Compton scattering amplitudes at energies below photoproduction threshold and fixed momentum transfer, following from (an upper bound on) the corresponding differential cross section above photoproduction threshold. The derivation involves the solution of an extremal problem in a certain space of vector - valued analytic functions. (author)

  8. Taming Tree Amplitudes In General Relativity

    CERN Document Server

    Benincasa, Paolo; Cachazo, Freddy; 10.1088/1126-6708/2007/11/057

    2008-01-01

    We give a proof of BCFW recursion relations for all tree-level amplitudes of gravitons in General Relativity. The proof follows the same basic steps as in the BCFW construction and it is an extension of the one given for next-to-MHV amplitudes by one of the authors and P. Svr\\v{c}ek in hep-th/0502160. The main obstacle to overcome is to prove that deformed graviton amplitudes vanish as the complex variable parameterizing the deformation is taken to infinity. This step is done by first proving an auxiliary recursion relation where the vanishing at infinity follows directly from a Feynman diagram analysis. The auxiliary recursion relation gives rise to a representation of gravity amplitudes where the vanishing under the BCFW deformation can be directly proven. Since all our steps are based only on Feynman diagrams, our proof completely establishes the validity of BCFW recursion relations. This means that many results in the literature that were derived assuming their validity become true statements.

  9. Cardiac phase: Amplitude analysis using macro programming

    International Nuclear Information System (INIS)

    The analysis of EKG gated radionuclide cardiac imaging data with Fourier amplitude and phase images is becoming a valuable clinical technique, demonstrating location, size, and severity of regional ventricular abnormalities. Not all commercially available nuclear medicine computer systems offer software for phase and amplitude analysis; however, many systems do have the capability of linear image arithmetic using simple macro commands which can easily be sequenced into stored macro-strings or programs. Using simple but accurate series approximations for the Fourier operations, macro programs have been written for a Digital Equipment Corporation Gamma-11 system to obtain phase and amplitude images from routine gated cardiac studies. In addition, dynamic cine-mode presentation of the onset of mechanical systole is generated from the phase data, using only a second set of macro programs. This approach is easily adapted to different data acquisition protocols, and can be used on any system with macro commands for image arithmetic. Key words: Fourier analysis, cardiac cycle, gated blood pool imaging, amplitude image, phase image

  10. Sum Rules for Parity Violating Compton Amplitudes

    Science.gov (United States)

    Lukaszuk, L.; Kurek, K.

    2006-03-01

    After discussion of legitimacy of the dispersive approach in the Standard Model sum rules (s.r.) for parity violating (p.v.) amplitudes are presented. These are s.r. for polarizabilities and p.v. analogue of the Gerasimov--Drell--Hearn sum rule. Phenomenological implications are reviewed.

  11. Simplifying the three point type I amplitude

    International Nuclear Information System (INIS)

    Full text: The superstring theory is the most promising model of the last decades for unifying all interactions of nature. Besides its importance, a covariant approach of quantization was an unsolved problem for a long time, until the development of the pure spinor formalism. In a previous work the type I effective action for supergravity was computed in this framework . In that work, the tree-level mixed amplitudes (for one closed string and two open strings) were computed. Roughly speaking, the basic steps followed in that analysis were: 1) write the amplitude involving the three vertex operators needed in the computation,2) use the cyclic symmetry to choose one closed and one open strings as fixed operators, 3) Simplify it by using OPE's inside the amplitude and 4), for the remaining terms, evaluate all combinations (term by term) with five theta's. For example, in step number 4, in order to make all necessary calculations, the GAMMA package (a program for MATHEMATICA) had to be used to evaluate products of gamma matrices inside the amplitude. The fact is that there is an important tool that have the power to simplify more these calculations: the cyclic symmetry prescription. It means that, no matter the three unintegrated vertex are, the result is the same for all possibilities you get. In this work we use this symmetry in the three point amplitude for choose the fermion operators as the unintegrated ones. This simplifies the computations in such a way that no prothe computations in such a way that no program is needed to find the right result, what gives a cleaner result. (author)

  12. Simplifying the three point type I amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Alencar, G.; Tahim, M.O.; Landim, R.R. [Universidade Estadual do Ceara (UECE), Fortaleza, CE (Brazil)

    2011-07-01

    Full text: The superstring theory is the most promising model of the last decades for unifying all interactions of nature. Besides its importance, a covariant approach of quantization was an unsolved problem for a long time, until the development of the pure spinor formalism. In a previous work the type I effective action for supergravity was computed in this framework . In that work, the tree-level mixed amplitudes (for one closed string and two open strings) were computed. Roughly speaking, the basic steps followed in that analysis were: 1) write the amplitude involving the three vertex operators needed in the computation,2) use the cyclic symmetry to choose one closed and one open strings as fixed operators, 3) Simplify it by using OPE's inside the amplitude and 4), for the remaining terms, evaluate all combinations (term by term) with five theta's. For example, in step number 4, in order to make all necessary calculations, the GAMMA package (a program for MATHEMATICA) had to be used to evaluate products of gamma matrices inside the amplitude. The fact is that there is an important tool that have the power to simplify more these calculations: the cyclic symmetry prescription. It means that, no matter the three unintegrated vertex are, the result is the same for all possibilities you get. In this work we use this symmetry in the three point amplitude for choose the fermion operators as the unintegrated ones. This simplifies the computations in such a way that no program is needed to find the right result, what gives a cleaner result. (author)

  13. Crack propagation under variable amplitude loading

    Scientific Electronic Library Online (English)

    Miloudi, Abdelkader; Zemri, Mokhtar; Benguediab, Mohamed; Mazari, Mohamed; Amrouche, Abdelwaheb.

    1161-11-01

    Full Text Available SciELO Brazil | Language: English Abstract in english Experience shows that a damage induced by a given cycle is dependent on the loading history. In this regard, the objective of this paper is to study and describe the phenomenology of the loading history on crack propagation. Different loading configuration has been considered for fatigue crack propa [...] gation of XC38 steel; overload cycles followed by underload and vice versa were considered during propagation. Measure of crack opening has been made using compliance method. It is shown that the main parameters which cause retardation are the residual compressive stresses and the crack closure. The finite element modeling is used to calculate the evolution of residual stress profiles before and after application of the overload-underload cycle. It corroborates the hypotheses on the mechanisms behind, including those proposed on the residual stresses at the crack tip.

  14. Thermal inertializing of solid incinerator residues

    International Nuclear Information System (INIS)

    Inertialization of residues is a key task of incinerators. Residues of conventional incineration processes may contain high levels of inorganic or organic pollutants and must be treated prior to recycling. the most effective process is thermal treatment above the melting point. This will destroy organic pollutants like dioxins/furans and pathogenic compounds, while the heavy metals will be partly volatilized. The glassy slag obtained as end product is low in heavy metals and more or less resistant to leaching. The The author describes a method for calculating activity coefficients of volatile components of diluted, liquid multicomponent systems. With these data, the data base for thermodynamic description of fluid mixtures was updated, and a set of characteristic data was established for describing transport in an inflatable module. Once the activity coefficients of interesting constituents of the slag are known along with the transport conditions in the volatilization process, it is possible to optimize the thermal treatment of critical ashes and dusts with a view to energy consumption and process control. In two different exemplary process concepts, the energy consumption for residue treatment is estimated. The processes proposed are compared with published process proposals, and their energy consumption is assessed in a comoparative study

  15. Experimental study on self-modulation of ion plasma oscillations

    International Nuclear Information System (INIS)

    Experimental study on the self-modulation of externally amplitude-modulated ion plasma oscillations is described. Oscillations were excited by applying an rf voltage with a frequency near the ion plasma frequency to a grid being a wall of the plasma container. The envelopes of such oscillations were observed to break up into several spikes if their amplitudes were above a value. Individual spikes thus formed were found to have similar properties to those of envelope solitons, although the spikes were observed not to move in the laboratory frame. The number of spikes per group was observed to depend strongly on various parameters. Frequency spectra of excited oscillations were studied over various amplitudes of the applied rf voltage. Comparison of these experimental results with theoretical ones indicates that the self-modulation of oscillations observed here occurs due to the modulational instability. (auth.)

  16. Study of the Residual Resistance of Superconducting Niobium Films at 1.5 GHz

    CERN Document Server

    Valente, A M; Calatroni, Sergio; Darriulat, Pierre; Peck, M A; Van't Hof, C A

    1999-01-01

    A study of the main potential contributions to the residual surface resistance of niobium-coated cavities is reviewed. They are the formation of hydride precipitates, the contamination by discharge gas atoms and the presence of macroscopic defects in the film, induced by defects in the substrate. It will be shown that residual resistances as low as those obtained for bulk niobium can be achieved, together with a very small dependence on the amplitude of the RF field.

  17. Multi-amplitude Differential Space-time Block Coding Scheme for Square/Non-Square Code Matrix in MIMO Systems

    Directory of Open Access Journals (Sweden)

    Xiangbin Yu

    2012-05-01

    Full Text Available Differential space-time coding (DSTC technique has become a good choice when channel estimations are difficult to obtain in multiple antennas system. On the basis of analyzing the existing DSTC schemes, by introducing multi-level quadrature amplitude modulation (MQAM and matrix transform method, we develop a multi-amplitude differential space-time block coding (STBC scheme for square or non-square code matrix in MIMO systems, and give the derivation of calculation formulae of the coding advantage in detail. The developed scheme can effectively avoid the performance loss of conventional DSTC schemes based on PSK modulation (i.e. single amplitude DSTC in high spectrum efficiency. It can be applied to non-square code matrix case, and thus overcomes the shortcoming that existing DSTC schemes are only suitable for square code matrix. Compared with single amplitude DSTC schemes, our scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes. Moreover, our scheme has linear decoding complexity, higher coding advantage, and higher code rate for more than two antennas. The simulations results show that the proposed scheme can provide lower BER than the existing single amplitude differential STBC schemes for both square and non-square code matrices.

  18. Bioenergy from sisal residues

    Energy Technology Data Exchange (ETDEWEB)

    Jungersen, G. [Dansk Teknologisk Inst. (Denmark); Kivaisi, A.; Rubindamayugi, M. [Univ. of Dar es Salaam (Tanzania, United Republic of)

    1998-05-01

    The main objectives of this report are: To analyse the bioenergy potential of the Tanzanian agro-industries, with special emphasis on the Sisal industry, the largest producer of agro-industrial residues in Tanzania; and to upgrade the human capacity and research potential of the Applied Microbiology Unit at the University of Dar es Salaam, in order to ensure a scientific and technological support for future operation and implementation of biogas facilities and anaerobic water treatment systems. The experimental work on sisal residues contains the following issues: Optimal reactor set-up and performance; Pre-treatment methods for treatment of fibre fraction in order to increase the methane yield; Evaluation of the requirement for nutrient addition; Evaluation of the potential for bioethanol production from sisal bulbs. The processing of sisal leaves into dry fibres (decortication) has traditionally been done by the wet processing method, which consumes considerable quantities of water and produces large quantities of waste water. The Tanzania Sisal Authority (TSA) is now developing a dry decortication method, which consumes less water and produces a waste product with 12-15% TS, which is feasible for treatment in CSTR systems (Continously Stirred Tank Reactors). (EG)

  19. MULTIGLUON AMPLITUDES IN THE HIGH-ENERGY LIMIT

    OpenAIRE

    Del Duca, Vittorio

    1995-01-01

    We give a unified description of tree-level multigluon amplitudes in the high-energy limit. We represent the Parke-Taylor amplitudes and the Fadin-Kuraev-Lipatov amplitudes in terms of color configurations that are ordered in rapidity on a two-sided plot. We show that for the helicity configurations they have in common the Parke-Taylor amplitudes and the Fadin-Kuraev-Lipatov amplitudes coincide.

  20. Integrable spin chains and scattering amplitudes

    International Nuclear Information System (INIS)

    In this review we show that the multi-particle scattering amplitudes in N=4 SYM at large Nc and in the multi-Regge kinematics for some physical regions have the high energy behavior appearing from the contribution of the Mandelstam cuts in the complex angular momentum plane of the corresponding t-channel partial waves. These Mandelstam cuts or Regge cuts are resulting from gluon composite states in the adjoint representation of the gauge group SU(Nc). In the leading logarithmic approximation (LLA) their contribution to the six point amplitude is in full agreement with the known two-loop result. The Hamiltonian for the Mandelstam states constructed from n gluons in LLA coincides with the local Hamiltonian of an integrable open spin chain. We construct the corresponding wave functions using the integrals of motion and the Baxter-Sklyanin approach. (orig.)

  1. Integrable spin chains and scattering amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Bartels, J.; Prygarin, A. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Lipatov, L.N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Petersburg Nuclear Physics Institute (Russian Federation); Sankt-Peterburgskij Univ., St. Petersburg (Russian Federation)

    2011-04-15

    In this review we show that the multi-particle scattering amplitudes in N=4 SYM at large N{sub c} and in the multi-Regge kinematics for some physical regions have the high energy behavior appearing from the contribution of the Mandelstam cuts in the complex angular momentum plane of the corresponding t-channel partial waves. These Mandelstam cuts or Regge cuts are resulting from gluon composite states in the adjoint representation of the gauge group SU(N{sub c}). In the leading logarithmic approximation (LLA) their contribution to the six point amplitude is in full agreement with the known two-loop result. The Hamiltonian for the Mandelstam states constructed from n gluons in LLA coincides with the local Hamiltonian of an integrable open spin chain. We construct the corresponding wave functions using the integrals of motion and the Baxter-Sklyanin approach. (orig.)

  2. Source amplitudes for active exterior cloaking

    International Nuclear Information System (INIS)

    The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the infinite region exterior to a set of circles defined by the relative positions of the sources. The results provide a direct solution to the inverse problem of determining the source amplitudes. They also define a broad class of non-radiating discrete sources. (paper)

  3. Limit on the pion distribution amplitude

    CERN Document Server

    Luna, E G S

    2014-01-01

    The pion distribution amplitude (DA) can be related to the fundamental QCD Green's functions as a function of the quark self-energy and the quark-pion vertex, which in turn are associated with the pion wave function through the Bethe-Salpeter equation. Considering the extreme hard asymptotic behavior in momentum space allowed for a pseudoscalar wave function, which is limited by its normalization condition, we compute the pion DA and its second moment. From the resulting amplitude, representing the field theoretical upper limit on the DA behavior, we calculate the photon-pion transition form factor $F_{\\pi\\gamma\\gamma^{\\ast}}(Q^{2})$. The resulting upper limit on the pion transition form factor is compared with existing data published by CLEO, BaBar and Belle collaborations.

  4. Optical twists in phase and amplitude

    DEFF Research Database (Denmark)

    Daria, Vincent R.; Palima, Darwin

    2011-01-01

    Light beams with helical phase profile correspond to photons having orbital angular momentum (OAM). A Laguerre-Gaussian (LG) beam is an example where its helical phase sets a phase-singularity at the optical axis and forms a ring-shaped transverse amplitude profile. Here, we describe a unique beam where both phase and amplitude express a helical profile as the beam propagates in free space. Such a beam can be accurately referred to as an optical twister. We characterize optical twisters and demonstrate their capacity to induce spiral motion on particles trapped along the twisters’ path. Unlike LG beams, the far field projection of the twisted optical beam maintains a high photon concentration even at higher values of topological charge. Optical twisters have therefore profound applications to fundamental studies of light and atoms such as in quantum entanglement of the OAM, toroidal traps for cold atoms and for optical manipulation of microscopic particles.

  5. Towards an amplitude analysis of exclusive ?? processes

    International Nuclear Information System (INIS)

    The potential of two photon processes to shed light on the parton content of resonances, we maintain, can only be realized in practice by moving towards an Amplitude Analysis of experimental data. By using the process ?? ? ?? as an example, the way to do this is discussed. Presently claimed uncertainties in the ?? width of even the well-known f2 (1270) are shown to be over-optimistic and the fitted couplings of the overlapping scalar states in the 1 GeV region meaningless. Only the use of Amplitude Analysis techniques on the new higher statistics data from SLAC and DESY can resolve these uncertainties and lead to definite and significant results. 37 refs., 18 figs

  6. Large amplitude waves and fields in plasmas

    International Nuclear Information System (INIS)

    In this review, based mostly on the results of the recent workshop on ''Large Amplitude Waves and Fields in Plasmas'' held at ICTP (Trieste, Italy) in May 1989 during the Spring College on Plasma Physics, I will mostly concentrate on underdense, cold, homogeneous plasmas, discussing some of the alternative (to fusion) uses of laser-plasma interaction. In Part I an outline of some basic non-linear processes is given, together with some recent experimental results. The processes are chosen because of their relevance to the applications or because new interesting developments have been reported at the ICTP workshop (or both). In Part II the excitation mechanisms and uses of large amplitude plasma waves are presented: these include phase-conjugation in plasmas, plasma based accelerators (beat-wave, plasma wake-field and laser wake-field), plasma lenses and plasma wigglers for Free Electron Lasers. (author)

  7. Bounds on scattering amplitudes and form factors

    International Nuclear Information System (INIS)

    In these lectures, some aspects, physical as well as mathematical, are discussed of several problems of bounds in the physics of particles. The problem of the determination of rigorous bounds on two-body scattering amplitudes, in the framework of Axiomatic Quantum Field Theory (AQFT) is discussed. One of the motivations for looking at such bounds could be to test experimentally the validity of the axioms of QFT, by comparing these bounds with experimental data. Needless to say, no violation has been observed so far. But it is remarkable that from general properties of scattering amplitudes such as analyticity, crossing and unitarity, one is able to get bounds on observable quantities that are quite close to experimental data. (Auth.)

  8. ZZ brane amplitudes from matrix models

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Akira; Tsuchiya, Asato [Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)]. E-mail: tsuchiya@phys.sci.osaka-u.ac.jp

    2005-02-01

    We study instanton contribution to the partition function of the one matrix model in the k-th multicritical region, which corresponds to the (2,2k-1) minimal model coupled to Liouville theory. The instantons in the one matrix model are given by local extrema of the effective potential for a matrix eigenvalue and identified with the ZZ branes in Liouville theory. We show that the 2-instanton contribution in the partition function is universal as well as the 1-instanton contribution and that the connected part of the 2-instanton contribution reproduces the annulus amplitudes between the ZZ branes in Liouville theory. Our result serves as another nontrivial check on the correspondence between the instantons in the one matrix model and the ZZ branes in Liouville theory, and also suggests that the expansion of the partition function in terms of the instanton numbers are universal and gives systematically ZZ brane amplitudes in Liouville theory. (author)

  9. Quadrupole and monopole large amplitude vibrations

    International Nuclear Information System (INIS)

    A set of nonlinear dynamical equations for quadrupole and monopole moments of nuclei is derived from the TDHF equation with the help of the so-called Wigner function moments. It allows the description of coupled large amplitude monopole and quadrupole vibrations. These equations are solved numerically for 208Pb and 40Ca in a model with separable forces. The giant quadrupole and monopole resonances are reproduced very well. However the essential feature of the large amplitude motion is the existence of multiphonon states. They are analyzed in detail. The classical and quantum aspects of the analytically solvable one-dimensional pure monopole model are studied to clarify the problem of the anharmonicity of the collective spectrum. 26 refs., 2 figs., 2 tabs

  10. Source amplitudes for active exterior cloaking

    OpenAIRE

    Norris, Andrew N.; Amirkulova, Feruza A.; Parnell, William J.

    2012-01-01

    The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the i...

  11. Finiteness of type II superstring amplitudes

    International Nuclear Information System (INIS)

    All possible divergences arising from vanishing dividing or handle geodesics are analysed for massless amplitudes for type II superstrings. In particular putative divergences arising from coincidence of interaction vertices are shown to cancel on integration over phases. Nor do any infinities arise when there are vanishing dividing geodesics. We conclude that type II superstrings are finite, and are excellent candidates to give a finite theory of quantum gravity. (orig.)

  12. Baryon poles in proton decay amplitudes

    International Nuclear Information System (INIS)

    The decay rate of the p ? ?0e+ mode is calculated in SU(5) grand unified theory using a pole model with proton and 1/2- baryon poles. Baryon-to-vacuum amplitudes are calculated in the framework of the MIT bag model. It is found that the partial decay rate [approx. equal to (5 x 1031 yr)-1] is close to the partial decay rates calculated by different methods. (orig.)

  13. Ward identities for amplitudes with reggeized gluons

    Energy Technology Data Exchange (ETDEWEB)

    Bartles, J. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Universidad Tecnica Federico Santa Maria, Valparaiso (Chile). Dept. de Fisica; Lipatov, L.N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; St. Petersburg Nuclear Physics Institute (Russian Federation); Vacca, G.P. [INFN, Sezione di Bologna (Italy)

    2012-05-15

    Starting from the effective action of high energy QCD we derive Ward identities for Green's functions of reggeized gluons. They follow from the gauge invariance of the effective action, and allow to derive new representations of amplitudes containing physical particles as well as reggeized gluons. We explicitly demonstrate their validity for the BFKL kernel, and we present a new derivation of the kernel.

  14. Automatic Generation of Tree Level Helicity Amplitudes

    OpenAIRE

    Stelzer, T.; Long, W. F.

    1994-01-01

    The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.

  15. Nucleon and $N^* (1535)$ Distribution Amplitudes

    CERN Document Server

    Braun, V M; Göckeler, M; Hagen, C; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schäfer, A; Schiel, R W; Schierholz, G; Stüben, H; Zanotti, J M

    2010-01-01

    The QCDSF collaboration has investigated the distribution amplitudes and wavefunction normalization constants of the nucleon and its parity partner, the $N^* (1535)$. We report on recent progress in the calculation of these quantities on configurations with two dynamical flavors of $\\mathcal{O}(a)$-improved Wilson fermions. New data at pion masses of approximately 270 MeV helps in significantly reducing errors in the extrapolation to the physical point.

  16. Annulus amplitude of FZZT branes revisited

    CERN Document Server

    Oh, Jae-Hyuk; Rim, Chaiho

    2011-01-01

    We revisit the annulus amplitude of FZZT branes with general matter sectors (r,s) using the recent development of matrix model and minimal Liouville gravity. Following the boundary description of the 1-matrix model and bulk resonance transformation between primary operators we find the consistency of the brane decomposition into (1,1)-branes. We also investigate the corresponding results obtained directly from the minimal Liouville gravity and demonstrate the perfect agreement with the matrix results.

  17. The pion-pion scattering amplitude

    OpenAIRE

    Pelaez, J. R.; Yndurain, F. J.

    2004-01-01

    We obtain reliable $\\pi\\pi$ scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy ($s^{1/2}\\leq1.42 {\\rm GeV}$) phase shifts and inelasticities with expressions that incorporate analyticity and unitarity. In particular, for the S wave with isospin~0, we discuss in detail several sets of experimental data. This provides low energy partial wa...

  18. Propagation of large amplitude pulsar waves

    International Nuclear Information System (INIS)

    The oblique vacuum model predicts a value of 3 for the braking index of the pulsar whereas the observed or computed values are different, a realistic model therefore has to include both the relativistic plasma outflow and the electromagnetic wave emission. The vacuum wave model has been changed to include self-consistent plasma effects in plane geometry and inhomogeneities linked to spherical geometry. This results in very restrictive conditions for the possibility of propagation of the large amplitude waves. (Auth.)

  19. Normalization Factors, Reflection Amplitudes and Integrable Systems

    OpenAIRE

    Fateev, V. A.

    2001-01-01

    We calculate normalization factors and reflection amplitudes in the W-invariant conformal quantum field theories. Using these CFT data we derive vacuum expectation values of exponential fields in affine Toda theories and related perturbed conformal field theories. We apply these results to evaluate explicitly the expectation values of order parameters in the field theories associated with statistical systems, like XY, Z_n-Ising and Ashkin-Teller models. The same results are ...

  20. Deep Inelastic Scattering at the Amplitude Level

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; /SLAC

    2005-08-04

    The deep inelastic lepton scattering and deeply virtual Compton scattering cross sections can be interpreted in terms of the fundamental wavefunctions defined by the light-front Fock expansion, thus allowing tests of QCD at the amplitude level. The AdS/CFT correspondence between gauge theory and string theory provides remarkable new insights into QCD, including a model for hadronic wavefunctions which display conformal scaling at short distances and color confinement at large distances.

  1. Pion distribution amplitude within the instanton model

    International Nuclear Information System (INIS)

    The leading-twist pion distribution amplitude is obtained at a low normalization scale of an order of the inverse average size of an instanton ?c. The pion dynamics, consistent with gauge invariance and low energy theorems, is considered within the instanton vacuum model. The results are QCD evolved to higher momentum-transfer values, and are in agreement with recent data from CLEO on pion transition form factor. We also show that previous calculations violate the axial Ward-Takahashi identity

  2. Continuous phase and amplitude holographic elements

    Science.gov (United States)

    Maker, Paul D. (inventor); Muller, Richard E. (inventor)

    1995-01-01

    A method for producing a phase hologram using e-beam lithography provides n-ary levels of phase and amplitude by first producing an amplitude hologram on a transparent substrate by e-beam exposure of a resist over a film of metal by exposing n is less than or equal to m x m spots of an array of spots for each pixel, where the spots are randomly selected in proportion to the amplitude assigned to each pixel, and then after developing and etching the metal film producing a phase hologram by e-beam lithography using a low contrast resist, such as PMMA, and n-ary levels of low doses less than approximately 200 micro-C/sq cm and preferably in the range of 20-200 micro-C/sq cm, and aggressive development using pure acetone for an empirically determined time (about 6 s) controlled to within 1/10 s to produce partial development of each pixel in proportion to the n-ary level of dose assigned to it.

  3. Transversity Amplitudes in Hypercharge Exchange Processes

    International Nuclear Information System (INIS)

    ' In this work we present several techniques developed for the extraction of the. Transversity amplitudes governing quasi two-body meson baryon reactions with hypercharge exchange. We review the methods used in processes having a pure spin configuration, as well as the more relevant results obtained with data from Kp and Tp interactions at intermediate energies. The predictions of the additive quark model and the ones following from exchange degeneracy and etoxicity are discussed. We present a formalism for amplitude analysis developed for reactions with mixed spin configurations and discuss the methods of parametric estimation of the moduli and phases of the amplitudes, as well as the various tests employed to check the goodness of the fits. The calculation of the generalized joint density matrices is given and we propose a method based on the generalization of the idea of multipole moments, which allows to investigate the structure of the decay angular correlations and establishes the quality of the fits and the validity of the simplifying assumptions currently used in this type of studies. (Author) 43 refs

  4. Identifying Key Residues for Protein Allostery through Rigid Residue Scan.

    Science.gov (United States)

    Kalescky, Robert; Liu, Jin; Tao, Peng

    2015-03-01

    Allostery is a ubiquitous process for protein regulatory activity in which a binding event can change a protein's function carried out at a distal site. Despite intensive theoretical and experimental investigation of protein allostery in the past five decades, effective methods have yet to be developed that can systematically identify key residues involved in allosteric mechanisms. In this study, we propose the rigid residue scan as a systematic approach to identify important allosteric residues. The third PDZ domain (PDZ3) in the postsynaptic density 95 protein (PSD-95) is used as a model system, and each amino acid residue is treated as a single rigid body during independent molecular dynamics simulations. Various indices based on cross-correlation matrices are used, which allow for two groups of residues with different functions to be identified. The first group is proposed as "switches" that are needed to "turn on" the binding effect of protein allostery. The second group is proposed as "wire residues" that are needed to propagate energy or information from the binding site to distal locations within the same protein. Among the nine residues suggested as important for PDZ3 intramolecular communication in this study, eight have been reported as critical for allostery in PDZ3. Therefore, the rigid residue scan approach is demonstrated to be an effective method for systemically identifying key residues in protein intramolecular communication and allosteric mechanisms. PMID:25437403

  5. Joint Acoustic and Modulation Frequency

    Directory of Open Access Journals (Sweden)

    Les Atlas

    2003-06-01

    Full Text Available There is a considerable evidence that our perception of sound uses important features which is related to underlying signal modulations. This topic has been studied extensively via perceptual experiments, yet there are few, if any, well-developed signal processing methods which capitalize on or model these effects. We begin by summarizing evidence of the importance of modulation representations from psychophysical, physiological, and other sources. The concept of a two-dimensional joint acoustic and modulation frequency representation is proposed. A simple single sinusoidal amplitude modulator of a sinusoidal carrier is then used to illustrate properties of an unconstrained and ideal joint representation. Added constraints are required to remove or reduce undesired interference terms and to provide invertibility. It is then noted that the constraints would also apply to more general and complex cases of broader modulation and carriers. Applications in single-channel speaker separation and in audio coding are used to illustrate the applicability of this joint representation. Other applications in signal analysis and filtering are suggested.

  6. Automobile shredder residue gasification.

    Science.gov (United States)

    De Filippis, Paolo; Pochetti, Fausto; Borgianni, Carlo; Paolucci, Martino

    2003-10-01

    Automobile Shredder Residue (ASR) shows a broad chemical composition owing to the presence of different materials, and its high organic content makes it interesting as a source of energy. In this work, a bench scale two-stage reactor is used for gasifying ASR. The reactor shows an efficient ASR gasification, avoiding the formation of difficult to manage char and tar and allowing an easy recovery of energy. The results of the investigation were used to test a simple model based on mass and energy balances and chemical equilibrium, predicting syngas composition including the presence of problematic elements such as sulphur and chlorine. Gasification data calculated by the model agree in a satisfactory way with the experimental ones. Due to the large variation in ASR composition, the model predicts that ASR gasification is industrially feasible only if a blend of ASR and RDF is used as a reactor feed. PMID:14661893

  7. Residual gas analyzer calibration

    Science.gov (United States)

    Lilienkamp, R. H.

    1972-01-01

    A technique which employs known gas mixtures to calibrate the residual gas analyzer (RGA) is described. The mass spectra from the RGA are recorded for each gas mixture. This mass spectra data and the mixture composition data each form a matrix. From the two matrices the calibration matrix may be computed. The matrix mathematics requires the number of calibration gas mixtures be equal to or greater than the number of gases included in the calibration. This technique was evaluated using a mathematical model of an RGA to generate the mass spectra. This model included shot noise errors in the mass spectra. Errors in the gas concentrations were also included in the valuation. The effects of these errors was studied by varying their magnitudes and comparing the resulting calibrations. Several methods of evaluating an actual calibration are presented. The effects of the number of gases in then, the composition of the calibration mixture, and the number of mixtures used are discussed.

  8. residue and shunting pinholes

    Science.gov (United States)

    Gorji, Nima E.

    2014-09-01

    The present work considers two observable phenomena through the experimental fabrication and electrical characterization of the rf-sputtered CdS/CdTe thin film solar cells that extremely reduce the overall conversion efficiency of the device: CdCl2 residue on the surface of the semiconductor and shunting pinholes. The former happens through nonuniform treatment of the As-deposited solar cells before annealing at high temperature and the latter occurs by shunting pinholes when the cell surface is shunted by defects, wire-like pathways or scratches on the metallic back contact caused from the external contacts. Such physical problems may be quite common in the experimental activities and reduce the performance down to 4-5 % which leads to dismantle the device despite its precise fabrication. We present our electrical characterization on the samples that received wet CdCl2 surface treatment (uniform or nonuniform) and are damaged by the pinholes.

  9. Thermionic modules

    Science.gov (United States)

    King, Donald B. (Albuquerque, NM); Sadwick, Laurence P. (Salt Lake City, UT); Wernsman, Bernard R. (Clairton, PA)

    2002-06-18

    Modules of assembled microminiature thermionic converters (MTCs) having high energy-conversion efficiencies and variable operating temperatures manufactured using MEMS manufacturing techniques including chemical vapor deposition. The MTCs incorporate cathode to anode spacing of about 1 micron or less and use cathode and anode materials having work functions ranging from about 1 eV to about 3 eV. The MTCs also exhibit maximum efficiencies of just under 30%, and thousands of the devices and modules can be fabricated at modest costs.

  10. Experimental determination of residual stress

    Science.gov (United States)

    Ferguson, Milton W.

    1991-01-01

    Residual stresses in finished parts have often been regarded as factors contributing to premature part failure and geometric distortions. Currently, residual stresses in welded structures and railroad components are being investigated. High residual stresses formed in welded structures due primarily to the differential contractions of the weld material as it cools and solidifies can have a profound effect on the surface performance of the structure. In railroad wheels, repeated use of the brakes causes high residual stresses in the rims which may lead to wheel failure and possible derailment. The goals of the study were: (1) to develop strategies for using x-ray diffraction to measure residual stress; (2) to subject samples of Inconel 718 to various mechanical and heat treatments and to measure the resulting stress using x-ray diffraction; and (3) to measure residual stresses in ferromagnetic alloys using magnetoacoustics.

  11. High-order UWB pulses scheme to generate multilevel modulation formats based on incoherent optical sources.

    Science.gov (United States)

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2013-11-18

    We present a high-order UWB pulses generator based on a microwave photonic filter which provides a set of positive and negative samples by using the slicing of an incoherent optical source and the phase inversion in a Mach-Zehnder modulator. The simple scalability and high reconfigurability of the system permit a better accomplishment of the FCC requirements. Moreover, the proposed scheme permits an easy adaptation to pulse amplitude modulation, bi phase modulation, pulse shape modulation and pulse position modulation. The flexibility of the scheme for being adaptable to multilevel modulation formats permits to increase the transmission bit rate by using hybrid modulation formats. PMID:24514405

  12. Materials recovery from shredder residues

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, E. J.; Jody, B. J.; Pomykala, J., Jr.

    2000-07-24

    Each year, about five (5) million ton of shredder residues are landfilled in the US. Similar quantities are landfilled in Europe and the Pacific Rim. Landfilling of these residues results in a cost to the existing recycling industry and also represents a loss of material resources that are otherwise recyclable. In this paper, the authors outline the resources recoverable from typical shredder residues and describe technology that they have developed to recover these resources.

  13. Study of the residual surface resistance of niobium films at 1.5 GHz

    CERN Document Server

    Calatroni, Sergio; Darriulat, Pierre; Peck, M A; Valente, A M; Van't Hof, C A

    2001-01-01

    Potential contributions to the residual surface resistance of niobium films exposed to 1.5 GHz microwaves are reviewed and studied. These include the oxidation of the film surface, the formation of hydride precipitates, the contamination by noble gas atoms and the presence of macroscopic film defects such as those resulting from the roughness of the substrate. Particular attention is given to the dependence of the residual resistance on the amplitude of the microwave. Results similar to those obtained for bulk niobium provide strong evidence against the conjecture that the small size of the film grains should be a fundamental limitation to the production of films having a low residual resistance.

  14. Modulating the Neutron Flux from a Mirror Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D D

    2011-09-01

    A 14-MeV neutron source based on a Gas-Dynamic Trap will provide a high flux of 14 MeV neutrons for fusion materials and sub-component testing. In addition to its main goal, the source has potential applications in condensed matter physics and biophysics. In this report, the author considers adding one more capability to the GDT-based neutron source, the modulation of the neutron flux with a desired frequency. The modulation may be an enabling tool for the assessment of the role of non-steady-state effects in fusion devices as well as for high-precision, low-signal basic science experiments favoring the use of the synchronous detection technique. A conclusion is drawn that modulation frequency of up to 1 kHz and modulation amplitude of a few percent is achievable. Limitations on the amplitude of modulations at higher frequencies are discussed.

  15. Virtual Color-Kinematics Duality: 6-pt 1-Loop MHV Amplitudes

    CERN Document Server

    Yuan, Ellis Ye

    2012-01-01

    We study 1-loop MHV amplitudes in N=4 super Yang-Mills theory and in N=8 supergravity. For Yang-Mills we find that the simple form for the full amplitude presented by Del Duca, Dixon and Maltoni naturally leads to one that has physical residues on all compact contours. After expanding the simple form in terms of standard scalar integrals, we introduce redundancies under certain symmetry considerations to impose the color-kinematics duality of Bern, Carrasco and Johansson (BCJ). For five particles we directly find the results of Carrasco and Johansson as well as a new compact form for the supergravity amplitude. For six particles we find that all kinematic dual Jacobi identities are encapsulated in a single functional equation relating the expansion coefficients. By the BCJ double-copy construction we obtain a formula for the corresponding N=8 supergravity amplitude. Quite surprisingly, all physical information becomes independent of the expansion coefficients modulo the functional equation. In other words, th...

  16. Virtual color-kinematics duality: 6-pt 1-loop MHV amplitudes

    Science.gov (United States)

    Yuan, Ellis Ye

    2013-05-01

    We study 1-loop MHV amplitudes in {N} = 4 super Yang-Mills theory and in {N} = 8 supergravity. For Yang-Mills we find that the simple form for the full amplitude presented by Del Duca, Dixon and Maltoni naturally leads to one that has physical residues on all compact contours. After expanding the simple form in terms of standard scalar integrals, we introduce redundancies under certain symmetry considerations to impose the color-kinematics duality of Bern, Carrasco and Johansson (BCJ). For five particles we directly find the results of Carrasco and Johansson as well as a new compact form for the supergravity amplitude. For six particles we find that all kinematic dual Jacobi identities are encapsulated in a single functional equation relating the expansion coefficients. By the BCJ double-copy construction we obtain a formula for the corresponding {N} = 8 super-gravity amplitude. Quite surprisingly, all physical information becomes independent of the expansion coefficients modulo the functional equation. In other words, there is no need to solve the functional equation at all. This is quite welcome as the functional equation we find, using our restricted set of redundancies, actually has no solutions. For this reason we call these results virtual color-kinematics duality. We end with speculations about the meaning of an interesting global vs. local feature of the functional equation and the situation at higher points.

  17. Module amenability for Banach modules

    Scientific Electronic Library Online (English)

    D, Ebrahimi Bagha; M, Amini.

    2011-06-01

    Full Text Available SciELO Chile | Language: English Abstract in spanish Se estudia el módulo de receptividad de los módulos de Banach. Esta es una generalización natural de la receptividad de Johnson de las álgebras de Banach. Como ejemplo se muestra que para un grupo abeliano discreto G l p(G) es receptivo como un G l p(G)- módulo, si y sólo si G es receptivo, donde l¹ [...] (G) es un álgebra de Banach con producto punto. Abstract in english We study the module amenability of Banach modules. This is a natural generalization of Johnson’s amenability of Banach algebras. As an example we show that for a discrete abelian group G, l p(G) is amenable as an l¹(G)-module if and only if G is amenable, where l¹(G) is a Banach algebra with pointwi [...] se multiplication.

  18. Valves Module

    Science.gov (United States)

    The Center for the Advancement of Process Technology presents this free sample module on valves in the process industries. The interactive resource includes 55 screens and will help learners with both the details of valve systems and the process technician's role in valve operation and maintenance.

  19. Simulation of Digital Modulation Techniques Using MATLAB

    Directory of Open Access Journals (Sweden)

    Neha Sharma, Yogendra Yadav

    2012-12-01

    Full Text Available In Digital modulation the message signal is in the digital form and the carrier wave is in sinusoidal form. In this technique the Amplitude, Frequency or Phase of carrier varies according to message (Baseband signal. There are various type of digital modulation technique like Amplitude Shift Keying (ASK, Phase Shift Keying (PSK, Frequency Shift Keying (FSK, Quadature Phase Shift Keying (QPSK, Differential Phase Shift Keying (DPSK and other digital demodulation technique. Simulation is the imitation of the operation of a real-world process or system over time. The act of simulating something first requires that a model be developed; this model represents the key characteristics or behaviors of the selected physical or abstract system or process. The model represents the system itself, whereas the simulation represents the operation of the system over time. Simulation is used in many contexts, such as simulation of technology for performance optimization, safety engineering, testing, training, education, and video games. So in this paper we will simulate and verify the waveform of modulating wave, carrier wave and modulated wave of Amplitude Shift Keying (ASK, Phase Shift Keying (PSK, Frequency Shift Keying FSK, Quadature Phase Shift keying (QPSK.

  20. Ethnic differences in electrocardiographic amplitude measurements

    International Nuclear Information System (INIS)

    There is a controversy regarding ethnic differences in electrocardiographic (ECG) patterns because of the potentially confounding socioeconomic, nutritional, environmental and occupational factors. We reviewed the first 1000 medical files of a multiethnic community, where all individuals shared similar living conditions. Only healthy adults age 15 to 60 years were included. Wave amplitudes were measured manually from the standard 12lead ECG. Minnesota coding was used. ECG from 597 subjects were included in the study: 350 Saudi Arabians, 95 Indians, 17 Sri-Lankans, 39 Filipinos, and 57 Caucasians; 349 were men. the mean +-SD of Sokolow-Lyon voltage (SLV) in men was signifcantly different among ethnic groups (2.9+-0.86, 2.64+-0.79, 2.73+-0.72, 3.23+-0.61, 2.94+-0.6, 2.58+-0.79 mV, P=0.0006, for Saudi's, Indians, Jordanians, Filipinos, Sri-Lankans, and Caucasians, respectively). SLV was similar among ethnic groups in women. The prevalence of early transition pattern was also different among ethnic groups in men but not women (15.8%, 34.6%, 17.9%, 21.7%, 35.3%, 26.8% in Suadi, Indian, Jordanian, Filipino, Sri-Lankan, and Caucasian, respectively, P=0.037). T wave amplitude was significantly different among ethnic groups in selected lead. ECG wave amplitude differs with ethnic region even when other factors are similar. Using SLV of 3.5 mV as a criterion may overestimate the incidence of left ventricular hypertrophy in some ethnic groups. The pattern of high R wave in lead roups. The pattern of high R wave in lead V1is common in healthy adults in certain ethnic groups. T wave height differs with ethnic origin and sex. (author)