Residual amplitude modulation in interferometric gravitational wave detectors.
Kokeyama, Keiko; Izumi, Kiwamu; Korth, William Z; Smith-Lefebvre, Nicolas; Arai, Koji; Adhikari, Rana X
2014-01-01
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 optomechanical spring, which also perturbs the sensing matrix. We use our simulations to derive requirements on RAM for the Advanced LIGO (aLIGO) detectors, and show that the RAM expected in aLIGO will not limit its sensitivity. PMID:24561943
International Nuclear Information System (INIS)
Three independent mechanisms are described that contaminate the phase-modulated pump beam of an optical frequency reference stabilized by modulation transfer spectroscopy (MTS) with residual amplitude modulation (RAM). The electro-optic modulator, the beam geometry and the absorption of the saturated medium all separately generate undesired RAM that degrades the accuracy of the optical frequency reference. An analysis is presented that shows how frequency shifts introduced by the different mechanisms can be evaluated in typical MTS set-ups and minimized. The analysis also shows how the detector phase can be used to measure the total RAM in the system and how the phase required to remove any remaining frequency offsets can be evaluated
Sathian, Juna; Jaatinen, Esa
2013-05-20
Residual amplitude modulation (RAM) is an unwanted noise source in electro-optic phase modulators. The analysis presented shows that while the magnitude of the RAM produced by a MgO:LiNbO(3) modulator increases with intensity, its associated phase becomes less well defined. This combination results in temporal fluctuations in RAM that increase with intensity. This behavior is explained by the presented phenomenological model based on gradually evolving photorefractive scattering centers randomly distributed throughout the optically thick medium. This understanding is exploited to show that RAM can be reduced to below the 10(-5) level by introducing an intense optical beam to erase the photorefractive scatter. PMID:23736449
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
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)
Pulse amplitude modulated chlorophyll fluorometer
Energy Technology Data Exchange (ETDEWEB)
Greenbaum, Elias; Wu, Jie
2015-12-29
Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.
Mechanical models of amplitude and frequency modulation
Energy Technology Data Exchange (ETDEWEB)
Bellomonte, L; Guastella, I; Sperandeo-Mineo, R M [GRIAF - Research Group on Teaching/Learning Physics, DI.F.TE.R. -Dipartimento di Fisica e Tecnologie Relative, University of Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy)
2005-05-01
This paper presents some mechanical models for amplitude and frequency modulation. The equations governing both modulations are deduced alongside some necessary approximations. Computer simulations of the models are carried out by using available educational software. Amplitude modulation is achieved by using a system of two weakly coupled pendulums, whereas the frequency modulation is obtained by using a pendulum of variable length. Under suitable conditions (small oscillations, appropriate initial conditions, etc) both types of modulation result in significantly accurate and visualized simulations.
Amplitude modulation of wind turbine noise
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).
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
Amplitude modulation of Langmuir waves: Vlasov simulation
Umeda, T.
2006-12-01
Mechanisms for the generation of Langmuir wave packets are studied by performing a one-dimensional electrostatic Vlasov simulation. The present simulation of a weak-electron-beam instability without ion dynamics suggests two new processes for the amplitude modulation of Langmuir waves. The beam instability excites Langmuir modes over a wide wavenumber range, but the saturation of the most unstable Langmuir mode "filters" the growth of sideband modes. Specific upper and lower sideband modes linearly grow to a high saturation level. Then the primary Langmuir mode is amplified and strongly modulated through interaction with the sideband modes.
Modulator-free quadrature amplitude modulation signal synthesis
Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O'Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan
2014-12-01
The ability to generate high-speed on-off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5?Gbit?s-1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on-off-keyed 10?Gbit?s-1 systems and is absolutely prohibitive for today’s (>)100?Gbit?s-1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions.
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 li...
Correlation of amplitude modulation to inflow characteristics
DEFF Research Database (Denmark)
Aagaard Madsen, Helge; Bertagnolio, Franck
2014-01-01
Amplitude modulation (AM) of noise from wind turbines and its more extreme version named “other amplitude modulation” OAM have been investigated intensively during the last few years due to the additional annoyance impact this type of noise has compared to broad band noise. In a recent published research by RenewableUK the hypothesis has been that one of the causes of OAM is transient stall on the blade due to non uniform inflow such as shear. Part of the RenewableUK research work was a contribution by DTU on analysis of data from the DANAERO MW experiment from 2009. In the DANAERO experiment a new 38.8m test blade for a 2MW NM80 turbine was manufactured and equipped with a massive instrumentation comprising flush mounted surface microphones, pressure taps and five hole pitot tubes. The correlation of the spectra from the surface microphones and the measured inflow angle (IA) confirmed the strong increase in the noise source for high IA. As only few 10min data sets were measured in the DANAERO project a data set with measured inflow angle from 2003 on the same turbine has been used to explore the statistical properties of AM and OAM based on assumed correlation to IA.
Factorization of residues of off-shell string amplitudes
International Nuclear Information System (INIS)
All normalization factors are supplied for the calculation of off-shell string amplitudes in the formalism of Cohen et al. Wave function normalization constants are determined from the residues of poles in the two-point function. For amplitudes with one or two strings off-shell and an arbitrary number of on-shell particles, the residue of a pole in an off-shell channel factorizes into the product of the square root of the wave function normalization constant and the correctly normalized amplitude with the particle in the relevant channel on-shell. Factorization requires the same relation between the coupling constant defined by the topological term in the action and the coupling constant appearing in vertex operators that was derived previously from unitarity of S-matrix elements. (orig.)
Quantum model for electro-optical amplitude modulation
Capmany, Jose; Fernandez-Pousa, Carlos R.
2011-01-01
We present a quantum model for electro-optic amplitude modulation, which is built upon quantum models of the main photonic components that constitute the modulator, that is, the guided-wave beamsplitter and the electro-optic phase modulator and accounts for all the different available modulator structures. General models are developed both for single and dual drive configurations and specific results are obtained for the most common configurations currently employed. Finally...
Quantum model for electro-optical amplitude modulation
Capmany, Jose; 10.1364/OE.18.025127
2011-01-01
We present a quantum model for electro-optic amplitude modulation, which is built upon quantum models of the main photonic components that constitute the modulator, that is, the guided-wave beamsplitter and the electro-optic phase modulator and accounts for all the different available modulator structures. General models are developed both for single and dual drive configurations and specific results are obtained for the most common configurations currently employed. Finally, the operation with two-photon input for the control of phase-modulated photons and the important topic of multicarrier modulation are also addressed.
Suprathreshold effects of adaptation produced by amplitude modulation
Wojtczak, Magdalena; Viemeister, Neal F.
2003-08-01
This work extends the study of adaptation to amplitude modulation (AM) to the perception of highly detectable modulation. A fixed-level matching procedure was used to find perceptually equivalent modulation depths for 16-Hz modulation imposed on a 1-kHz standard and a 4-kHz comparison. The modulation depths in the two stimuli were compared before and after a 10-min exposure to a 1-kHz tone (adaptor) 100% modulated in amplitude at different rates. For modulation depths of 63% (20 log m=-4) and smaller, the perceived modulation depth was reduced after exposure to the adaptor that was modulated at the same rate as the standard. The size of this reduction expressed as a difference between the post- and pre-exposure AM depths was similar to the increase in AM-detection threshold observed after adaptation. Postexposure suprathreshold modulation depth was not appreciably reduced when the modulation depth of the standard was large (approached 100%). A much smaller or no reduction in the perceived modulation depth was also observed when the modulation rates of the adaptor and the standard tone were different. The tuning of the observed effect of the adaptor appears to be much sharper than the tuning shown by modulation-masking results.
San Paulo, Álvaro; García García, Ricardo
2001-01-01
Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the...
International Nuclear Information System (INIS)
In many situations of interest amplitude modulation AFM is characterized by the coexistence of two solutions with different physical properties. Here, we compare the performance of those solutions in the imaging of cobalt nanoparticles. We show that imaging with the high amplitude solution implies an irreversible deformation of the nanoparticles while repeated imaging with the low solution does not produce noticeable changes in the nanoparticles. Theoretical simulations show that the maximum tip-surface force in the high amplitude solution is about 14 nN while in the low amplitude solution is about -4 nN. We attribute the differences in the high and low amplitude images to the differences in the exerted forces on the sample
Amplitude Modulated Sinusoidal Signal Decomposition for Audio Coding
DEFF Research Database (Denmark)
Christensen, M. G.; Jacobson, A.; Andersen, S. V.; Jensen, Søren Holdt
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 critic...
Amplitude modulated sinusoidal signal decomposition for audio coding
Christensen, Mads Græsbøll; Jakobsson, Andreas; Andersen, Søren Vang; Jensen, Søren Holdt
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 cr...
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.
Amplitude Modulation in the ? Sct star KIC 7106205
Directory of Open Access Journals (Sweden)
Bowman Dominic. M.
2015-01-01
Full Text Available The ? Sct star KIC 7106205 showed amplitude modulation in a single p mode, whilst all other p and g modes remained stable in amplitude and phase over 1470 d of the Kepler dataset. The data were divided into 30 time bins of equal length and a series of consecutive Fourier transforms was calculated. A fixed frequency, calculated from a least-squares fit of all data, allowed amplitude and phase for every mode in each time bin to be tracked. The missing p mode energy was not transferred to any other visible modes.
AMPLITUDE AND PHASE MODULATION FOR ULTRASONIC WIRELESS COMMUNICATION
Directory of Open Access Journals (Sweden)
Nan Gao
2014-04-01
Full Text Available 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 for wireless communication in air, instead of using electromagnetic field wave. In order to find an advisable modulation method for ultrasound wireless communication, Amplitude modulation method and Phased modulation method has been test.
Superposed pulse amplitude modulation for visible light communication.
Li, J F; Huang, Z T; Zhang, R Q; Zeng, F X; Jiang, M; Ji, Y F
2013-12-16
We propose and experimentally demonstrate a novel modulation scheme called superposed pulse amplitude modulation (SPAM) which is low-cost, insensitive to non-linearity of light emitting diode (LED). Multiple optical pulses transmit parallelly from different spatial position in the LED array and overlap linearly in free space to realize SPAM. With LED arrangement, the experimental results show that using the modulation we proposed the data rate of 120 Mbit/s with BER 1 × 10(-3) can be achieved with an optical blue filter and RC post-equalization. PMID:24514674
Computational evaluation of amplitude modulation for enhanced magnetic nanoparticle hyperthermia.
Soetaert, Frederik; Dupré, Luc; Ivkov, Robert; Crevecoeur, Guillaume
2015-10-01
Magnetic nanoparticles (MNPs) can interact with alternating magnetic fields (AMFs) to deposit localized energy for hyperthermia treatment of cancer. Hyperthermia is useful in the context of multimodality treatments with radiation or chemotherapy to enhance disease control without increased toxicity. The unique attributes of heat deposition and transfer with MNPs have generated considerable attention and have been the focus of extensive investigations to elucidate mechanisms and optimize performance. Three-dimensional (3D) simulations are often conducted with the finite element method (FEM) using the Pennes' bioheat equation. In the current study, the Pennes' equation was modified to include a thermal damage-dependent perfusion profile to improve model predictions with respect to known physiological responses to tissue heating. A normal distribution of MNPs in a model liver tumor was combined with empirical nanoparticle heating data to calculate tumor temperature distributions and resulting survival fraction of cancer cells. In addition, calculated spatiotemporal temperature changes were compared among magnetic field amplitude modulations of a base 150-kHz sinusoidal waveform, specifically, no modulation, sinusoidal, rectangular, and triangular modulation. Complex relationships were observed between nanoparticle heating and cancer tissue damage when amplitude modulation and damage-related perfusion profiles were varied. These results are tantalizing and motivate further exploration of amplitude modulation as a means to enhance efficiency of and overcome technical challenges associated with magnetic nanoparticle hyperthermia (MNH). PMID:26351900
Response of plasmonic terahertz detectors to amplitude modulated signals
Rupper, Greg; Rudin, Sergey; Shur, Michael
2015-09-01
We present theoretical study of the response of two-dimensional gated electron gas to an amplitude modulated signals with carrier frequency in the terahertz range. The model is based on complete hydrodynamic equations, and includes effects of viscosity, pressure gradients and thermal transport in the conduction channel of a high electron mobility semiconductor transistor (HEMT). The modulation response was evaluated as a function of modulation frequency fM for a wide range of mobility values. Maximum modulation frequency fMAX was evaluated as a function of channel mobility, with typical values of fMAX in the subterahertz range of frequencies. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet all the requirements for applications as terahertz detectors and modulators in ultra high-speed wireless communication circuits.
About the Phasor Pathways in Analogical Amplitude Modulation
de Oliveira, H M
2015-01-01
The Phasor diagrams have long been used in Physics and Engineering. In telecommunications, this is particularly useful to clarify how the modulations work. This paper addresses rotating phasor pathways derived from different standard Amplitude Modulation Systems (e.g. A3E, H3E, J3E, C3F). A cornucopia of algebraic curves is then derived assuming a single tone or a double tone modulation signal. The ratio of the frequency of the tone modulator (fm) and carrier frequency (fc) is considered in two distinct cases, namely: fm/fc=1. The geometric figures are some sort of Lissajours figures. Different shapes appear looking like epicycloids (including cardioids), rhodonea curves, Lemniscates, folium of Descartes or Lam\\'e curves. The role played by the modulation index is elucidated in each case.
Cusack, Benedict J; Sheard, Benjamin S; Shaddock, Daniel A.; Gray, Malcolm B; Lam, Ping Koy; Whitcomb, Stan E
2003-01-01
We report on the analysis and prototype-characterization of a dual-electrode electro-optic modulator that can generate both amplitude and phase modulations with a selectable relative phase, termed a universally tunable modulator (UTM). All modulation states can be reached by tuning only the electrical inputs, facilitating real-time tuning, and the device is shown to have good suppression and stability properties. A mathematical analysis is presented, including the developmen...
Pulse Amplitude and Delay Modulation: Design and performance analysis
Slaiman, Iskandar; Tang, Tong Boon; Hamid, Nor Hisham
2015-06-01
Power efficient modulation techniques have previously been proposed to provide the uplink in visible light communication systems. However, such techniques have poor bandwidth utilization as multiple bits are mapped to single narrow pulse. When the bandwidth is limited, it has been found that degradation in optical power becomes very high and data rate poor. In this paper we introduce a new modulation technique called Pulse Amplitude and Delay Modulation (PADM). We compare its performance with Dual Header Pulse Interval Modulation (DH-PIM) that has the best reported bandwidth efficiency. Experiment results show that the data rate could be enhanced from 3.2 kps to 4.3 kbs using a red link (640 nm) under same error rate. This suggests PADM has better bandwidth efficiency than DH-PIM.
Modulator-free quadrature amplitude modulation signal synthesis
Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O’Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan
2014-01-01
The ability to generate high-speed on–off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5?Gbit?s?1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modula...
Vlasov simulation of amplitude-modulated Langmuir waves
Umeda, Takayuki
2006-09-01
Mechanisms for the generation of Langmuir wave packets are studied by performing a one-dimensional electrostatic Vlasov simulation. The present simulation of a weak-electron-beam instability without ion dynamics suggests two new processes for the amplitude modulation of Langmuir waves. The beam instability excites Langmuir modes over a wide wave number range, but the saturation of the most unstable Langmuir mode "filters" the growth of sideband modes. Specific upper and lower sideband modes linearly grow to a high saturation level. Then the primary Langmuir mode is amplified and strongly modulated through interaction with the sideband modes.
Vlasov simulation of amplitude-modulated Langmuir waves
International Nuclear Information System (INIS)
Mechanisms for the generation of Langmuir wave packets are studied by performing a one-dimensional electrostatic Vlasov simulation. The present simulation of a weak-electron-beam instability without ion dynamics suggests two new processes for the amplitude modulation of Langmuir waves. The beam instability excites Langmuir modes over a wide wave number range, but the saturation of the most unstable Langmuir mode 'filters' the growth of sideband modes. Specific upper and lower sideband modes linearly grow to a high saturation level. Then the primary Langmuir mode is amplified and strongly modulated through interaction with the sideband modes
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
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.
Amplitude Modulation in the ZZ Ceti Star GD 244
Bognár, Zs.; Paparó, M.; Molnár, L.; Plachy, E.; Sódor, Á.
2015-06-01
Previous studies of GD 244 revealed seven pulsation frequencies (two doublets and three single periods) in the light variations of the star. The data obtained at McDonald Observatory between 2003 and 2006, and our additional measurements in 2006 and 2007 at Konkoly Observatory, allow the investigation of the long-term pulsational behaviour of GD 244. We found that the 307.1 s period component of one of the doublets show long-term, periodic amplitude modulation with a time scale of ˜ 740 days. Possible explanations are that nonlinear resonant mode coupling is operating among the rotationally split frequency components, or two modes, unresolved in the yearly data are excited at ˜ 307.1 s. This is the first time that such long-term periodic amplitude modulation is published on a ZZ Ceti star.
Amplitude Modulation in the ZZ Ceti Star GD 244
Bognár, Zs; Molnár, L; Plachy, E; Sódor, Á
2015-01-01
Previous studies of GD 244 revealed seven pulsation frequencies (two doublets and three single periods) in the light variations of the star. The data obtained at McDonald Observatory between 2003 and 2006, and our additional measurements in 2006 and 2007 at Konkoly Observatory, allow the investigation of the long-term pulsational behaviour of GD 244. We found that the 307.1 s period component of one of the doublets show long-term, periodic amplitude modulation with a time scale of ~740 days. Possible explanations are that nonlinear resonant mode coupling is operating among the rotationally split frequency components, or two modes, unresolved in the yearly data are excited at ~307.1 s. This is the first time that such long-term periodic amplitude modulation is published on a ZZ Ceti star.
Optical field terahertz amplitude modulation by graphene nanoribbons
Zhang, Hong; Miyamoto, Yoshiyuki; Cheng, Xinlu; Rubio, Angel
2015-11-01
In this study, first-principles time-dependent density functional theory calculations were used to demonstrate the possibility to modulate the amplitude of the optical electric field (E-field) near a semiconducting graphene nanoribbon. A significant enhancement of the optical E-field was observed 3.34 Å above the graphene nanoribbon sheet, with an amplitude modulation of approximately 100 fs, which corresponds to a frequency of 10 THz. In general, a six-fold E-field enhancement could be obtained, which means that the power of the obtained THz is about 36 times that of incident UV light. We suggest the use of semiconducting graphene nanoribbons for converting visible and UV light into a THz signal.
Texture in amplitude modulated (AM) and phase derivative (PD) echograms
International Nuclear Information System (INIS)
The information about the condition of parenchymal tissues is obscured by the performance characteristics of echographic equipment. The authors investigated by realistic 3-D simulations the so-called beam diffraction effects on two echographic imaging modalities: amplitude modulated (AM) and phase derivative (PD) echograms. Furthermore the modification of the image texture by attenuation was quantified. In order to assess the potentials of statistical analysis of texture for medical diagnostics the effects caused by varying the density of scattering particles in a homogeneous medium were studied. It is concluded, that unless beam diffraction effects are either prevented, or adequately corrected for, quantitative texture analysis is not meaningful. In addition, the data have to be corrected for the nonlinear and time dependent amplifier characteristics. Data-acquisition and pre-processing equipment performing these tasks has been developed at the authors' laboratory
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.
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 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.
High-efficiency electro-optic amplitude modulation with delayed coherent addition.
Ohmae, Noriaki; Moriwaki, Shigenori; Mio, Norikatsu
2011-01-15
Amplitude modulation of laser light is required for resonant sideband extraction employed in gravitational-wave detectors. Amplitude modulation with electro-optic phase modulators is realized by interferometric phase-to-amplitude conversion. Although two outputs modulated at opposite phases to each other are obtained, usually only one of them is utilized and the other is abandoned. The reuse of this abandoned light improves the power efficiency of the modulation. This can be realized by inverting the modulation phase of one output with a delay line and adding it to the other coherently. Moreover, this system selects a high-efficiency operating point and modulates the light in a linear range. We demonstrate that the modulation system can be operated with a power loss that is due only to the losses of the optical components. PMID:21263512
Optical binary switch and amplitude modulator micromirror arrays
Kolesar, Edward S., Jr.; Allen, Peter B.; Boydston, Noah C.; Howard, Jeffrey T.; Ko, Simon Y.; Wilken, Josh M.
1999-09-01
Five types of micromirror arrays were designed and fabricated using a three-level, polysilicon, surface micromachined, micro-electromechanical systems (MEMS) process. The electrostatically deflectable micromirror designs included arrays of simple cantilever beams, torsion beams, tethered (piston-style) beams, circular membranes, and oval membranes. The smallest micromirror element was the simple cantilever beam, measuring 50 micrometer square. The largest micromirror element was the oval membrane; it possessed an active optical surface that was 320 micrometer by 920 micrometer. Each of the remaining micromirror designs have gold-coated polysilicon optical surfaces with geometries between these two limits. Electrostatically induced vertical deflections on the order of 2.75 micrometer were achieved. The torsion beam micromirror design exhibits both in-plane and out-of-plane deflection. The other micromirror designs only manifest in-plane deflections. The modeling phase focused on the microdynamical behavior of the torsion beam micromirror. The IntelliCADR finite element analysis program was used to generate a plot of the micromirror's deflection (d) versus applied direct current voltage (V). The data was least-squares fitted to the well- established V varies direct as d3/2 relationship. A resonant frequency analysis predicted an approximate switching speed of 6 microseconds. The reliability (number of operational cycles) of each micromirror design, when operated with a rectified 60 Hz alternating current (ac) signal, was measured to exceed more than 1 million flexure events. Experimental evidence supporting the potential for using micromirrors as binary optical switches and amplitude modulators is also addressed.
Trellis-coded pulse amplitude modulation for indoor visible light communication
Wang, Yu; Yang, Aiying; Wu, Yongsheng; Feng, Lihui; Sun, Yu-nan; Li, Yankun
2013-12-01
Trellis-coded pulse-amplitude modulation (TC-PAM) is applied in visible light communication (VLC) system using RGB-LED. Based on natural modulation, we propose a modified modulation to yield performance enhancement. Further, a decoding method of combing soft-decision Viterbi algorithm with most significant bit (MSB) decoding is developed. Finally, the results of Monte-Carlo simulation are presented to verify the best modulation and decoding method among the mentioned modulation and decoding techniques.
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.
International Nuclear Information System (INIS)
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
DEFF Research Database (Denmark)
Eiselt, Nicklas; Griesser, Helmut
2015-01-01
Numerical and experimental investigations are undertaken to analyze and compare the performance of different equalizers for four-level pulse amplitude modulation, which is considered a promising candidate for the next generation of data center interconnects.
Dugué, Pierre; Le Bouquin Jeannès, Régine; Faucon, Gérard
2007-01-01
Amplitude modulation is an important feature of communication sounds. A phenomenological model of the auditory pathway that reproduces amplitude modulation coding from the outer ear to the inferior colliculus is presented. It is based on Hewitt and Meddis' work. To improve the temporal coding for high level stimuli, high spontaneous rate and low spontaneous rate auditory nerve fibers innervate chopper cells of the cochlear nucleus. Wideband inhibitory interneurons which limit high spontaneous...
Miyamoto, Tatsuya; Yada, Hiroyuki; Yamakawa, Hiromichi; Okamoto, Hiroshi
2013-01-01
Ferroelectrics sometimes show large electro-optical and non-linear optical effects, available for polarization rotation and frequency conversion of light, respectively. If the amplitude of ferroelectric polarization is modulated in the picosecond time domain, terahertz repetition of optical switching via electro-optical and non-linear optical effects would be achieved. Here we show that polarization amplitude can be rapidly modulated by a terahertz electric field in an organic ferroelectric, ...
Amplitude control of solid-state modulators for precision fast kicker applications
International Nuclear Information System (INIS)
A solid-state modulator with very fast rise and fall times, pulse width agility, and multi-pulse burst and intra-pulse amplitude adjustment capability for use with high speed electron beam kickers has been designed and tested at LLNL (Lawrence Livermore National Laboratory). The modulator uses multiple solid-state modules stacked in an inductive-adder configuration. Amplitude adjustment is provided by controlling individual modules in the adder, and is used to compensate for transverse e-beam motion as well as the dynamic response and beam-induced steering effects associated with the kicker structure. A control algorithm calculates a voltage based on measured e-beam displacement and adjusts the modulator to regulate beam centroid position. This paper presents design details of amplitude control along with measured performance data from kicker operation on the ETA-II accelerator at LLNL. (author)
Amplitude Control of Solid-State Modulators for Precision Fast Kicker Applications
International Nuclear Information System (INIS)
A solid-state modulator with very fast rise and fall times, pulse width agility, and multi-pulse burst and intra-pulse amplitude adjustment capability for use with high speed electron beam kickers has been designed and tested at LLNL. The modulator uses multiple solid-state modules stacked in an inductive-adder configuration. Amplitude adjustment is provided by controlling individual modules in the adder, and is used to compensate for transverse e-beam motion as well as the dynamic response and beam-induced steering effects associated with the kicker structure. A control algorithm calculates a voltage based on measured e-beam displacement and adjusts the modulator to regulate beam centroid position. This paper presents design details of amplitude control along with measured performance data from kicker operation on the ETA-II accelerator at LLNL
Czech Academy of Sciences Publication Activity Database
Pokorný, Pavel; Náhlík, Luboš; Huta?, Pavel
Vol. C. Amsterdam : Elsevier Ltd, 2015 - (Papuga, J.; Ruži?ka, M.), s. 380-385 ISSN 1877-7058. - (Procedia Engineering. 101). [VAL 2015 - International Conference on Material and Component Performance under Variable Amplitude Loading /3./. Praha (CZ), 23.03.2015-26.03.2015] R&D Projects: GA MŠk(CZ) EE2.3.20.0214 Institutional support: RVO:68081723 Keywords : railway axle * residual fatigue lifetime * fatigue crack * EA4T Subject RIV: JL - Materials Fatigue, Friction Mechanics http://www.sciencedirect.com/science/article/pii/S187770581500644X
A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...
Plasma based optical guiding of an amplitude-modulated electromagnetic beam
Singh, Mamta; Gupta, D. N.
2015-06-01
We propose the stronger optical guiding of an electromagnetic beam in a plasma by considering the amplitude modulation of the fundamental beam. With the advent of high power source of electromagnetic radiation, the electron velocity in a plasma may become quite large (comparable to the light velocity in free space). Thus, the effect of relativistic mass variation must be taken into account. The relativistic effect of the laser propagation in a plasma leads to self-focusing because of the dielectric constant of a plasma being an increasing function of the intensity. The ponderomotive force of the laser beam pushes the electrons out of the region of high intensity, which reduces the local electron density and increases the plasma dielectric function further, leading to even more selffocusing of the laser. In this work, we consider a short pulse laser of finite spot size as an amplitude modulation in time. Our findings show an efficient optical guiding mechanism based on amplitude modulation signal propagation in plasmas. Medium nonlinearity becomes stronger if an amplitude modulated beam is introduced, which contributes significantly in laser guiding in plasmas. Furthermore, the rate of laser self-focusing is increased with modulation index due the fact of stronger Kerr effect. The study related to amplitude modulated optical signal may be useful for communication technology.
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)
Analysis of amplitude modulation atomic force microscopy in aqueous salt solutions
International Nuclear Information System (INIS)
Highlights: • Imaging contrast during AM-AFM performed in salt solutions is numerically analyzed. • Imaging contrast is only marginally improved (?15%) at high amplitude setpoints. • Sample indentation and maximum interaction force values remain relatively unaffected. - Abstract: We present a numerical analysis of amplitude modulation atomic force microscopy in aqueous salt solutions, by considering the interaction of the microscope tip with a model sample surface consisting of a hard substrate and soft biological material through Hertz and electrostatic double layer forces. Despite the significant improvements reported in the literature concerning contact-mode atomic force microscopy measurements of biological material due to electrostatic interactions in aqueous solutions, our results reveal that only modest gains of ?15% in imaging contrast at high amplitude setpoints are expected under typical experimental conditions for amplitude modulation atomic force microscopy, together with relatively unaffected sample indentation and maximum tip–sample interaction values
Amplitude modulation of sound from wind turbines under various meteorological conditions.
Larsson, Conny; Öhlund, Olof
2014-01-01
Wind turbine (WT) sound annoys some people even though the sound levels are relatively low. This could be because of the amplitude modulated "swishing" characteristic of the turbine sound, which is not taken into account by standard procedures for measuring average sound levels. Studies of sound immission from WTs were conducted continually between 19 August 2011 and 19 August 2012 at two sites in Sweden. A method for quantifying the degree and strength of amplitude modulation (AM) is introduced here. The method reveals that AM at the immission points occur under specific meteorological conditions. For WT sound immission, the wind direction and sound speed gradient are crucial for the occurrence of AM. Interference between two or more WTs could probably enhance AM. The mechanisms by which WT sound is amplitude modulated are not fully understood. PMID:24437746
Superpixel-based spatial amplitude and phase modulation using a digital micromirror device
Sebastianus A. Goorden; Jacopo Bertolotti; Allard P. Mosk
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. We combine square regions of nearby micromirrors into superpixels by low pass filtering in a Fourier plane of the DMD. At each superpixel we are able to independently modulate the phase and the amplitude of light, while retaining a high resolution and the very high speed of a DMD. The method achieves a measured f...
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- ...
Energy Technology Data Exchange (ETDEWEB)
Ow, Y.S., E-mail: g0601170@nus.edu.s [Physics Department, National University of Singapore, Lower Kent Ridge Road, Singapore 119260 (Singapore); Breese, M.B.H.; Leng, Y.R.; Azimi, S.; Teo, E.J. [Physics Department, National University of Singapore, Lower Kent Ridge Road, Singapore 119260 (Singapore); Sun, X.W. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)
2010-05-01
Silicon has been machined on lateral resolutions of micrometers and on depth resolutions of nanometers using a recently-developed process based on ion irradiation and electrochemical anodisation. Here we investigate its use as a recording medium for computer generated hologram patterns. We describe the fabrication of both amplitude and phase binary modulated reflective computer generated hologram patterns on a silicon surface with pixel sizes of 5 mum. We further discuss the use of micromachined silicon to variably modulate both amplitude and phase in a continuous, rather than a binary fashion.
International Nuclear Information System (INIS)
Silicon has been machined on lateral resolutions of micrometers and on depth resolutions of nanometers using a recently-developed process based on ion irradiation and electrochemical anodisation. Here we investigate its use as a recording medium for computer generated hologram patterns. We describe the fabrication of both amplitude and phase binary modulated reflective computer generated hologram patterns on a silicon surface with pixel sizes of 5 ?m. We further discuss the use of micromachined silicon to variably modulate both amplitude and phase in a continuous, rather than a binary fashion.
Evidence of amplitude modulation due to Resonant Mode Coupling in the delta Scuti star KIC5892969
Forteza, S Barceló; Cortés, T Roca; García, R A
2015-01-01
A study of the star KIC5892969 observed by the Kepler satellite is presented. Its three highest amplitude modes present a strong amplitude modulation. The aim of this work is to investigate amplitude variations in this star and their possible cause. Using the 4 years-long observations available, we obtained the frequency content of the full light curve. Then, we studied the amplitude and phase variations with time using shorter time stamps. The results obtained are compared with the predicted ones for resonant mode coupling of an unstable mode with lower frequency stable modes. Our conclusion is that resonant mode coupling is consistent as an amplitude limitation mechanism in several modes of KIC5892969 and we discuss to which extent it might play an important role for other delta Scuti stars.
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.
International Nuclear Information System (INIS)
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
Energy Technology Data Exchange (ETDEWEB)
Rahman, Ata-ur-, E-mail: ata797@yahoo.com [Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan); Department of Physics, Islamia College Peshawar, Khyber Pakhtunkhwa (Pakistan); Kerr, Michael Mc, E-mail: mjamckerr@gmail.com; Kourakis, Ioannis, E-mail: IoannisKourakisSci@gmail.com [Centre for Plasma Physics, Department of Physics and Astronomy, Queen' s University Belfast, BT7 1NN Northern Ireland (United Kingdom); El-Taibany, Wael F., E-mail: eltaibany@hotmail.com [Department of Physics, Faculty of Science, Damietta University, New Damietta, P.O. Box 34517 (Egypt); Department of Physics, College of Science for Girls in Abha, King Khalid University, P.O. Box 960, Abha (Saudi Arabia); Qamar, A., E-mail: anisaqamar@gmail.com [Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan)
2015-02-15
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.
The effects of continuous and amplitude-modulated radiofrequency electromagnetic waves on calcium efflux from 45Ca preloaded frog hearts were examined. rog hearts, electrically stimulated at their natural beating frequency, were exposed for 30 min to 240 MHz radiowaves in a Crawf...
Radar transponder operation with compensation for distortion due to amplitude modulation
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.
NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS
International Nuclear Information System (INIS)
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 have 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 artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts of acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.
A Compact QPSK Modulator with Low Amplitude and Phase Imbalance for Remote Sensing Applications
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.
O’Connor, Kevin N.; Johnson, Jeffrey S; Niwa, Mamiko; Noriega, Nigel C.; Marshall, Elizabeth A.; Sutter, Mitchell .L.
2011-01-01
Previous observations show that humans outperform non-human primates on some temporally-based auditory discrimination tasks, suggesting there are species differences in the proficiency of auditory temporal processing among primates. To further resolve these differences we compared the abilities of rhesus macaques and humans to detect sine-amplitude modulation (AM) of a broadband noise carrier as a function of both AM frequency (2.5 Hz–2 kHz) and signal duration (50–800 ms), under similar test...
Schreiner, C E; Urbas, J V
1988-01-01
The responses of neuronal clusters to amplitude-modulated tones were studied in five auditory cortical fields of the anesthetized cat: the primary auditory field (AI), second auditory field (AII), anterior auditory field (AAF), posterior auditory field (PAF) and the ventro-posterior auditory field (VPAF). Modulation transfer functions (MTFs) for amplitude-modulated tones were obtained at 172 cortical locations. MTFs were constructed by measuring firing rate (rate-MTFs) and response synchronization (synchronization-MTFs) to sinusoidal and rectangular waveform modulation of CF-tones. The MTFs were characterized by their 'best-modulation frequency' (BMF) and a measure of their quality of 'sharpness' (Q2dB). These characteristics were compared for the five fields. Rate and synchronization MTFs for sinusoidal and rectangular modulation produced similar estimates of BMF and Q2dB. Comparison of averaged BMFs between the cortical fields revealed relatively high BMFs in AAF (mean: 31.1 Hz for synchronization to sinusoidal AM) and moderately high BMFs in AI (14.2 Hz) whereas BMFs encountered in AII, VPAF and PAF were generally low (7.0, 5.2, and 6.8 Hz). The MTFs were relatively broadly tuned (low Q2dB) in AAF and sharper in a low modulation group containing AII, PAF and VPAF. The ventro-posterior field was the most sensitive to changes in the modulation waveform. We conclude that there are significant differences between auditory cortical fields with respect to their temporal response characteristics and that the assessment of these response characteristics reveals important aspects of the functional significance of auditory cortical fields for the coding and representation of complex sounds. PMID:3350774
International Nuclear Information System (INIS)
High voltage, solid state, inductive adder, pulse generators have found increasing application as fast kicker pulse modulators for charged particle beams. The solid state, inductive adder, pulse generator is similar in operation to the linear induction accelerator. The main difference is that the solid state, adder couples energy by transformer action from multiple primaries to a voltage summing stalk, instead of an electron beam. Ideally, the inductive adder produces a rectangular voltage pulse at the load. In reality, there is usually some voltage variation at the load due to droop on primary circuit storage capacitors, or, temporal variations in the load impedance. Power MOSFET circuits have been developed to provide analog modulation of the output voltage amplitude of a solid state, inductive adder, pulse generator. The modulation is achieved by including MOSFET based, variable subtraction circuits in the multiple primary stack. The subtraction circuits can be used to compensate for voltage droop, or, to tailor the output pulse amplitude to provide a desired effect in the load. Power MOSFET subtraction circuits have been developed to modulate short, temporal (60-400 ns), voltage and current pulses. MOSFET devices have been tested up to 20 amps and 800 Volts with a band pass of 50 MHz. An analog modulation cell has been tested in a five cell high, voltage adder stack
Resonance monochromatization of transverse amplitude-modulated waves in a plasma
International Nuclear Information System (INIS)
Resonance interaction of plasma particles with transverse nonmonochromatic waves for which the group velocity coincides with the rate of energy transfer is considered on the basis of dynamical invariants of charged particles existing in the plane electromagnetic waves. The effect of decreasing of amplitude modulation (monochromatization) existing in such waves is studied both in a homogeneous plasma with rare collisions and a inhomogeneous collisionless plasma. It is shown that the effect of collisionless monochromatization in the inhomogeneous plasma is more significant and can lead to appearing of accelerated particles with the total absorption of amplitude modulation. The accuracy of preservation of the adiabatic invariant describing the confinement of the captured particles is investigated. It is shown the adiabatic invariant is preserved with an exponential accuracy while the condition of adiabaticity is fulfilled
Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light
Gruji?, Z D
2013-01-01
In recent years diode laser sources have become widespread and reliable tools in magneto-optical spectroscopy. In particular, laser-driven atomic magnetometers have found a wide range of practical applications. More recently, so-called magnetically silent variants of atomic magnetometers have been developed. While in conventional magnetometers the magnetic resonance transitions between atomic sublevels are phase-coherently driven by a weak oscillating magnetic field, silent magnetometers use schemes in which either the frequency (FM) or the amplitude (AM) of the light beam is modulated. Here we present a theoretical model that yields algebraic expressions for the parameters of the multiple resonances that occur when either amplitude-, frequency- or polarization-modulated light of circular polarization is used to drive the magnetic resonance transition in a transverse magnetic field. The relative magnitudes of the resonances that are observed in the transmitted light intensity at harmonic m of the Larmor frequ...
Maillard, J.; Sansonetti, P.
1992-01-01
The emission properties of an Amplitude Modulated diffraction limited external cavity multi-stripe high power laser diode are here reported. When resolving the resulting electric phase in the far field, a stabilization of a factor of 10 is obtained compared to the free running laser diode. Such a device is of interest for free space optical communication and range-finding. An original method based on white-light interferometry is also reported for measuring the reflection coefficient of the a...
Zhelyazkova, V.; Hogan, S. D.
2015-01-01
Dipole-dipole interactions between helium atoms in Rydberg-Stark states with principal quantum number $n=53$ and approximately linear Stark energy shifts, resulting from induced electric dipole moments of approximately 7900 D, have been investigated experimentally. The experiments were performed in pulsed supersonic metastable helium beams, with particle number densities of up to $\\sim10^9$ cm$^{-3}$. In the presence of amplitude-modulated, radio-frequency electric fields, c...
Amplitude modulation depth discrimination in hearing-impaired and normal-hearing listeners
DEFF Research Database (Denmark)
Ewert, Stephan D.; Volmer, Jutta; Dau, Torsten; Verhey, Jesko
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)...
Broadband homonuclear TOCSY with amplitude and phase-modulated RF mixing schemes
Energy Technology Data Exchange (ETDEWEB)
Kirschstein, Anika; Herbst, Christian; Riedel, Kerstin; Carella, Michela; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai [Fritz Lipmann Institute, Research Group Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany)], E-mail: raman@fli-leibniz.de
2008-04-15
We have explored the design of broadband scalar coupling mediated {sup 13}C-{sup 13}C and cross-relaxation suppressed {sup 1}H-{sup 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 deg. 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 {sup 1}H-{sup 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.
Broadband homonuclear TOCSY with amplitude and phase-modulated RF mixing schemes
International Nuclear Information System (INIS)
We have explored the design of broadband scalar coupling mediated 13C-13C and cross-relaxation suppressed 1H-1H 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 deg. 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 1H-1H 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
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.
Differential pulse amplitude modulation for multiple-input single-output OWVLC
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.
International Nuclear Information System (INIS)
The correspondance between amplitude and frequency modulations for a synchrocyclotron R.F. Voltage is firstly established. Optimal shapes are determined for these modulations for the Orsay synchrocyclotron. Shape of the rotative condenser static blades is then calculated to obtain the desired frequency modulation. Comparison is made between expected and obtained data. Values of working parameters are then proposed
Catalano, George D.
1998-06-01
The effects of noise modulation on the power spectral density functions of a sinusoidal wave are calculated in closed form. Frequency, phase, and amplitude modulation are considered. Noise processes are modeled using Butterworth filters of various integer orders. Increasing the order of the Butterworth filter increases the signal-to-noise ratio of the modulated sinusoidal wave.
Miyamoto, Tatsuya; Yada, Hiroyuki; Yamakawa, Hiromichi; Okamoto, Hiroshi
2013-01-01
Ferroelectrics sometimes show large electro-optical and non-linear optical effects, available for polarization rotation and frequency conversion of light, respectively. If the amplitude of ferroelectric polarization is modulated in the picosecond time domain, terahertz repetition of optical switching via electro-optical and non-linear optical effects would be achieved. Here we show that polarization amplitude can be rapidly modulated by a terahertz electric field in an organic ferroelectric, tetrathiafulvalene-p-chloranil (TTF-CA). In this compound, alternately stacked donor (TTF) and acceptor (CA) molecules are dimerized via the spin-Peierls mechanism, and charge transfer within each dimer results in a new type of ferroelectricity called electronic-type ferroelectricity. Using a terahertz field, the intradimer charge transfer is strongly modulated, producing a subpicosecond change in the macroscopic polarization, which is demonstrated by transient reflectivity and second-harmonic generation measurements. Subsequently, coherent oscillation of the dimeric molecular displacements occur, which is explained by the modulation of the spin moment of each molecule. PMID:24131938
Energy Technology Data Exchange (ETDEWEB)
Sell, J. F.; Gulyuz, K.; Sprouse, G. D. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794 (United States)
2009-12-15
Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized {sup 208-210}Fr ion beams at beam energies of 5 keV and intensities of 10{sup 5} s{sup -1}. Efficient neutralization ({>=}80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.
Sell, J. F.; Gulyuz, K.; Sprouse, G. D.
2009-12-01
Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized F208-210r ion beams at beam energies of 5 keV and intensities of 105 s-1. Efficient neutralization (?80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.
Heteronuclear J cross-polarisation in liquids using amplitude and phase modulated mixing sequences
Energy Technology Data Exchange (ETDEWEB)
Kirschstein, Anika; Herbst, Christian; Riedel, Kerstin; Carella, Michela; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai [Leibniz Institute for Age Research, Fritz Lipmann Institute, Research group Biomolecular NMR spectroscopy (Germany)], E-mail: raman@fli-leibniz.de
2008-04-15
The design of mixing sequences for heteronuclear J cross-polarisation in the liquid state has been examined employing supercycles of amplitude/phase modulated RF pulses. The Fourier coefficients defining the modulation profiles of the pulses were optimised numerically so as to achieve efficient magnetisation transfer within the desired range of resonance offsets. A variety of supercycles, pulsewidths and RF field strengths were considered in implementing heteronuclear anisotropic and isotropic mixing sequences. The coherence transfer characteristics of the sequences obtained were evaluated by numerical simulations. The experimental performances of the sequences were tested by measurements carried out on a moderate sized protein at 750 MHz. The results presented demonstrate that the approach adopted in this study can be employed effectively to tailor, as per the experimental requirements and constraints, the RF-field modulation profiles of the pulses constituting the mixing scheme for generating heteronuclear J cross-polarisation sequences.
Heteronuclear J cross-polarisation in liquids using amplitude and phase modulated mixing sequences
International Nuclear Information System (INIS)
The design of mixing sequences for heteronuclear J cross-polarisation in the liquid state has been examined employing supercycles of amplitude/phase modulated RF pulses. The Fourier coefficients defining the modulation profiles of the pulses were optimised numerically so as to achieve efficient magnetisation transfer within the desired range of resonance offsets. A variety of supercycles, pulsewidths and RF field strengths were considered in implementing heteronuclear anisotropic and isotropic mixing sequences. The coherence transfer characteristics of the sequences obtained were evaluated by numerical simulations. The experimental performances of the sequences were tested by measurements carried out on a moderate sized protein at 750 MHz. The results presented demonstrate that the approach adopted in this study can be employed effectively to tailor, as per the experimental requirements and constraints, the RF-field modulation profiles of the pulses constituting the mixing scheme for generating heteronuclear J cross-polarisation sequences
Nelson, Paul C.; Carney, Laurel H.
2006-01-01
Neural responses to amplitude-modulated (AM) tones in the unanesthetized rabbit inferior colliculus (IC) were studied in an effort to establish explicit relationships between physiological and psychophysical measures of temporal envelope processing. Specifically, responses to variations in modulation depth (m) at the cell’s best modulation frequency, with and without modulation maskers, were quantified in terms of average rate and synchronization to the envelope over the entire perceptual dyn...
Directory of Open Access Journals (Sweden)
Yunlong Yang
2013-01-01
Full Text Available In order to solve the limitation of data rate caused by long rise and fall time of light emitting diodes, m-ary return-to-zero optical pulse amplitude modulation is proposed in this paper for improving the bandwidth efficiency of indoor visible light communication. M-ary return-to-zero optical pulse amplitude modulation transmits information through a subtle change of illumination intensity and supports both flicker mitigation and dimming control functions. An indoor communication link establishing process is introduced as a parameter training method based on the principle of successive approximation. Theoretical analysis shows that, m-ary return-to-zero optical pulse amplitude modulation can be used to achieve higher bandwidth efficiency without sacrificing the symbol error rate and bit error rate performance of an indoor visible light communication system. When the ratio of a_slot-a_BS is 0.1, then m-ary return-to-zero optical pulse amplitude modulation can provide 1.47 times bandwidth efficiency than that of on-off keying, 3.5 times than that of digital pulse interval modulation and 5.9 times than that of pulse position modulation. M-ary return-to-zero optical pulse amplitude modulation can be used as a candidate bandwidth efficiency modulation scheme to improving data rate of an indoor visible light communication system.
Yunlong Yang; Shengyang He; Guanghui Ren
2013-01-01
In order to solve the limitation of data rate caused by long rise and fall time of light emitting diodes, m-ary return-to-zero optical pulse amplitude modulation is proposed in this paper for improving the bandwidth efficiency of indoor visible light communication. M-ary return-to-zero optical pulse amplitude modulation transmits information through a subtle change of illumination intensity and supports both flicker mitigation and dimming control functions. An indoor communication link establ...
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.
Energy Technology Data Exchange (ETDEWEB)
Santos, Sergio [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Barcons, Victor [Departament de Disseny i Programacio de Sistemes Electronics, UPC - Universitat Politecnica de Catalunya Av. Bases, 61, 08242 Manresa (Spain); Verdaguer, Albert [Centre d' Investigacio en Nanociencia i Nanotecnologia (CIN2) (CSIC-ICN), Esfera UAB, Campus de la UAB, Edifici CM-7, 08193-Bellaterra, Catalunya (Spain); Chiesa, Matteo [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307 (United States)
2011-12-01
In ambient conditions, nanometric water layers form on hydrophilic surfaces covering them and significantly changing their properties and characteristics. Here we report the excitation of subharmonics in amplitude modulation atomic force microscopy induced by intermittent water contacts. Our simulations show that there are several regimes of operation depending on whether there is perturbation of water layers. Single period orbitals, where subharmonics are never induced, follow only when the tip is either in permanent contact with the water layers or in pure noncontact where the water layers are never perturbed. When the water layers are perturbed subharmonic excitation increases with decreasing oscillation amplitude. We derive an analytical expression which establishes whether water perturbations compromise harmonic motion and show that the predictions are in agreement with numerical simulations. Empirical validation of our interpretation is provided by the observation of a range of values for apparent height of water layers when subharmonic excitation is predicted.
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.
Regime of a wideband phase-amplitude modulation in a CW magnetron transmitter with a phase control
Kazakevich, G; Chase, B; Pasquinelli, R; Yakovlev, V
2014-01-01
A model of the CW high-power transmitter, utilizing frequency-locked magnetrons with a phase control studied initially as a prototype of controllable in phase and power an RF source for intensity-frontier superconducting linacs, was considered for telecommunication as a model of magnetron source, acceptable for a wideband phase-amplitude modulation at a precisely stable carrier frequency. The R&D conducted with CW, 2.45 GHz, 1 kW, microwave oven magnetrons demonstrated that the frequency locking of the magnetrons by the phase-modulated signal provides wideband phase and amplitude modulation at the modulating frequency at least up to 3 MHz and large magnitude, keeping the carrier frequency precisely stable, without broadening of the spectral line width. Performed experiments with power combining verified applicability of the transmitter based on the frequency-locked magnetrons for wideband phase and amplitude modulation, which may be used for telecommunication. Results of the experiments are described in t...
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.
Temporal coding of 200% amplitude modulated signals in the ventral cochlear nucleus of cat.
Rhode, W S
1994-06-15
The quasiperiodicity in the acoustic waveform in speech and music is a pervasive feature in our acoustic environment. The use of 200% amplitude modulated (AM) signals allows the study of rate and temporal envelope coding using three equal amplitude components, a situation that is frequently approximated in natural vocalizations. The recordings reported here were made in the ventral cochlear nucleus of the cat, a site of auditory signal feature enhancement and the origin of several ascending auditory pathways. The discharge rate vs modulation frequency relation was nearly always all-pass in shape for all unit types indicating that discharge rate is not a code for modulation frequency. Onset cells, especially onset-choppers and onset-I units, exhibited remarkable phase locking to the signal envelope, nearly to the exclusion of phase locking to the AM components. They exhibited lowpass temporal modulation transfer functions (tMTF) that occasionally had corner frequencies greater than 1 kHz. Primary-like, primary-like with notch, and onset-L units all exhibited considerable variability in their coding properties with tMTFs that varied from lowpass to bandpass in shape. The bandpass shape became more frequent with increasing stimulus levels. A common feature in cochlear nucleus units was less sensitivity to the level of the AM stimulus than is present in the auditory nerve. Phase locking to the envelope persisted over a wider range of stimulus levels than rate changes in a subset of the units studied. The tMTFs for a 100% sinusoidally modulated, spectrally-flat noise was similar in amplitude and bandwidth to those obtained for AM stimuli. The tMTF was relatively insensitive to carrier frequencies different than the unit characteristic frequency. AM synchrony vs level curves exhibited systematic shifts that equaled or exceeded dynamic rate shifts that occur with increasing levels of a noise masker. Phase locking to the envelope was robust under a wide variety of signal conditions in all unit types. The ordering of response types based on the maximum of the tMTF is onset-I = onset-chop > choppers = primarylike-with-notch = onset-L > primarylike. PMID:7928738
Strickland, E A; Dhar, S
2000-08-01
Experiments were performed to determine under what conditions quasi-frequency-modulated (QFM) noise and random-sideband noise are suitable comparisons for AM noise in measuring a temporal modulation transfer function (TMTF). Thresholds were measured for discrimination of QFM from random-sideband noise and AM from QFM noise as a function of sideband separation. In the first experiment, the upper spectral edge of the noise stimuli was at 2400 Hz and the bandwidth was 1600 Hz. For sideband separations up to 256 Hz, at threshold sideband levels for discriminating AM from QFM noise, QFM was indiscriminable from random-sideband noise. For the largest sideband separation used (512 Hz), listeners may have used within-stimulus envelope correlation in the QFM noise to discriminate it from the random-sideband noise. Results when stimulus bandwidth was varied suggest that listeners were able to use this cue when the carrier was wider than a critical band, and the sideband separation approached the carrier bandwidth. Within-stimulus envelope correlation was also present in AM noise, and thus QFM noise was a suitable comparison because it made this cue unusable and forced listeners to use across-stimulus envelope differences. When the carrier bandwidth was less than a critical band or was wideband, QFM noise and random-sideband noise were equally suitable comparisons for AM noise. When discrimination thresholds for QFM and random-sideband noise were converted to modulation depth and modulation frequency, they were nearly identical to those for discrimination of AM from QFM noise, suggesting that listeners were using amplitude modulation cues in both cases. PMID:10955640
Laing, Mark; Rees, Adrian; Vuong, Quoc C.
2015-01-01
The temporal congruence between auditory and visual signals coming from the same source can be a powerful means by which the brain integrates information from different senses. To investigate how the brain uses temporal information to integrate auditory and visual information from continuous yet unfamiliar stimuli, we used amplitude-modulated tones and size-modulated shapes with which we could manipulate the temporal congruence between the sensory signals. These signals were independently modulated at a slow or a fast rate. Participants were presented with auditory-only, visual-only, or auditory-visual (AV) trials in the fMRI scanner. On AV trials, the auditory and visual signal could have the same (AV congruent) or different modulation rates (AV incongruent). Using psychophysiological interaction analyses, we found that auditory regions showed increased functional connectivity predominantly with frontal regions for AV incongruent relative to AV congruent stimuli. We further found that superior temporal regions, shown previously to integrate auditory and visual signals, showed increased connectivity with frontal and parietal regions for the same contrast. Our findings provide evidence that both activity in a network of brain regions and their connectivity are important for AV integration, and help to bridge the gap between transient and familiar AV stimuli used in previous studies.
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.
Annoyance of wind-turbine noise as a function of amplitude-modulation parameters
DEFF Research Database (Denmark)
Ioannidou, Christina; Santurette, Sébastien
Amplitude modulation (AM) has been suggested as an important factor for the perceived annoyance of wind-turbine noise (WTN). Two AM types, typically referred to as “normal AM” and “other AM,” depending on the AM extent and frequency region, have been proposed to characterize WTN AM. The extent to which AM depth, frequency, and type affect WTN annoyance is a matter of debate. In most subjective studies, the temporal variations of WTN AM have not been considered. Here, a sinusoidally modulated WTN model accounting for temporal AM variations was used to generate realistic artificial stimuli in which the AM depth, frequency, and type, while determined from real on-site recordings, could be varied systematically. Subjective listening tests with such stimuli showed that a reduction in AM depth, quantified by the modulation depth spectrum, led to a significant decrease in annoyance. When the spectrotemporal characteristics of the original far-field stimuli were included in the model and the temporal AM variations were taken into account by varying the modulation index over time, neither AM frequency nor AM type were found to significantly affect annoyance. These findings suggest that the effect of AM parameters on WTN annoyance may depend on the intermittent nature of WTN AM
Driving Rydberg-Rydberg transitions with an amplitude-modulated optical lattice
Moore, Kaitlin; Anderson, Sarah; Raithel, Georg
2014-05-01
We demonstrate a novel spectroscopic method that couples Rydberg states using an amplitude-modulated optical lattice. The method is fundamentally different from traditional microwave spectroscopy: it engages the A2-term rather than the Ap -term of the atom-field interaction Hamiltonian. The method allows us to drive microwave transitions between Rydberg states with optical spatial resolution, and it is not subject to the usual electric-dipole selection rules. Both features are attractive for quantum computing and precision metrology, such as measuring an improved value for the dipolar polarizibility of the Rb ionic core. In the experiment, cold Rb Rydberg atoms are first excited and confined in an optical lattice of wavelength 1064 nm. Then, the electric-quadrupole transition 58 S --> 59 S is driven by modulating the intensity of the optical lattice using a tunable electro-optic fiber modulator. Maximum population transfer occurs at a lattice modulation frequency of 38.768610(30) GHz, in close agreement with calculations. We briefly explain the theoretical background of the new spectroscopic method, show experimental results and discuss applications. We acknowledge support from DOE SCGF and NSF.
International Nuclear Information System (INIS)
Calcium (45Ca2+) efflux was studied from preloaded cortex in cats immobilized under local anesthesia, and exposed to a 3.0-mW/cm2 450-MHz field, sinusoidally amplitude modulated at 16 Hz modulation depth 85%). Tissue dosimetry showed a field of 33 V/m in the interhemispheric fissure (rate of energy deposition 0.29 W/kg). Field exposure lasted 60 min. By comparison with controls, efflux curves from field exposed brains were disrupted by waves of increased 45Ca2+ efflux. These waves were irregular in amplitude and duration, but many exhibited periods of 20-30 min. They continued into the postexposure period. Binomial probability analysis indicates that the field-exposed efflux curves constitute a different population from controls at a confidence level of 0.96. In about 70% of cases, initiation of field exposure was followed by increased end-tidal CO2 excretion for about 5 min. However, hypercapnea induced by hypoventilation did not elicit increased 45Ca2+ efflux. Thus this increase with exposure does not appear to arise as a secondary effect of raised cerebral CO2 levels. Radioactivity measurements in cortical samples after superfusion showed 45Ca2+ penetration at about 1.7 mm/hr, consistent with diffusion of the ion in free solution
Luo, Huan; Wang, Yadong; Poeppel, David; Simon, Jonathan Z
2007-12-01
Complex natural sounds (e.g., animal vocalizations or speech) can be characterized by specific spectrotemporal patterns the components of which change in both frequency (FM) and amplitude (AM). The neural coding of AM and FM has been widely studied in humans and animals but typically with either pure AM or pure FM stimuli. The neural mechanisms employed to perceptually unify AM and FM acoustic features remain unclear. Using stimuli with simultaneous sinusoidal AM (at rate f(AM) = 37 Hz) and FM (with varying rates f(FM)), magnetoencephalography (MEG) is used to investigate the elicited auditory steady-state response (aSSR) at relevant frequencies (f(AM), f(FM), f(AM) + f(FM)). Previous work demonstrated that for sounds with slower FM dynamics (f(FM) modulation" encoding. This study explores the neural coding mechanism for stimuli with faster FM dynamics ( 5 Hz), there is a transition from pure phase modulation encoding to a single-upper-sideband (SSB) response (at frequency f(AM) + f(FM)) pattern. We propose that this unexpected SSB response can be explained by the additional involvement of subsidiary AM encoding responses simultaneously to, and in quadrature with, the ongoing phase modulation. These results, using MEG to reveal a possible neural encoding of specific acoustic properties, demonstrate more generally that physiological tests of encoding hypotheses can be performed noninvasively on human subjects, complementing invasive, single-unit recordings in animals. PMID:17898148
Khaleghi, Salman
Technology has empowered people in all walks of life to generate, store, and communicate enormous amounts of data. Recent technological advances in high-speed backbone data networks, together with the growing trend toward bandwidth-demanding applications such as data and video sharing, cloud computing, and data collection systems, have created a need for higher capacities in signal transmission and signal processing. Optical communication systems have long benefited from the large bandwidth of optical signals (beyond tera-hertz) to transmit information. Through the use of optical signal processing techniques, this Ph.D. dissertation explores the potential of very-high-speed optics to assist electronics in processing huge amounts of data at high speeds. Optical signal processing brings together various fields of optics and signal processing---nonlinear devices and processes, analog and digital signals, and advanced data modulation formats---to achieve high-speed signal processing functions that can potentially operate at the line rate of fiber optic communications. Information can be encoded in amplitude, phase, wavelength, polarization, and spatial features of an optical wave to achieve high-capacity transmission. Many advances in the key enabling technologies have led to recent research in optical signal processing for digital signals that are encoded in one or more of these dimensions. Optical Kerr nonlinearities have femto-second response times that have been exploited for fast processing of optical signals. Various optical nonlinearities and chromatic dispersions have enabled key sub-system applications such as wavelength conversion, multicasting, multiplexing, demultiplexing, and tunable optical delays. In this Ph.D. dissertation, we employ these recent advances in the enabling technologies for high-speed optical signal processing to demonstrate various techniques that can process phase- and amplitude-encoded optical signals at the line rate of optics. We use nonlinear media, such as highly nonlinear fiber, periodically poled lithium niobate, and semiconductor optical amplifiers, for nonlinear mixing of optical signals. We propose and experimentally demonstrate a novel, fully tunable optical tapped-delay-line that is a key building block for signal processing functions. Applications such as finite impulse response filtering, equalization, correlation (pattern recognition), discrete Fourier transform, digital-to-analog conversion, and flexible optical signal conversion and generation are shown. The phase- and amplitude-preserving nature of the demonstrated techniques, together with their wide-tuning range, allows for processing of optical signals that carry different modulation formats with different data rates. The reconfigurability may apply to future optical networks that carry heterogeneous traffic with different modulation formats and baud rates.
Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; El-Din, Mohamed Gamal
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
Directory of Open Access Journals (Sweden)
Cal Francis Rabang
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.
Decoding Finger Flexion using amplitude modulation from band-specific ECoG
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.
Tong, Youwan; Zeng, Hualin; Li, Liyan; Zhou, Yan
2012-10-10
In this paper we propose a novel, improved, phase generated carrier (PGC) demodulation algorithm based on the PGC-differential-cross-multiplying approach (PGC-DCM). The influence of phase modulation amplitude variation and light intensity disturbance (LID) on traditional PGC demodulation algorithms is analyzed theoretically and experimentally. An experimental system for remote no-contact microvibration measurement is set up to confirm the stability of the improved PGC algorithm with LID. In the experiment, when the LID with a frequency of 50 Hz and the depth of 0.3 is applied, the signal-to-noise and distortion ratio (SINAD) of the improved PGC algorithm is 19 dB, higher than the SINAD of the PGC-DCM algorithm, which is 8.7 dB. PMID:23052073
Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions
Clément, P.-Y.; Baraduc, C.; Ducruet, C.; Vila, L.; Chshiev, M.; Diény, B.
2015-09-01
Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.
Amplitude-modulated noise: an empirical model for the radio radiation received from pulsars
International Nuclear Information System (INIS)
The radio radiation received from pulsars shows erratic variations over time and frequency. Experimentally these have been characterized by the autocorrelation function of the observed intensity and radio power spectrum. This paper gives theoretical expressions for these functions, under the assumption that the received radiation is described by random Gaussian noise that has been amplitude modulated. Such a model contains no coherence in time, other than that introduced by interstellar dispersion and the receiver bandpass, and has been implicitly assumed by many observers. The conclusions are a specific test for unresolved pulse components, which are easily confused with system noise, and a test for the significance of pulsar spectrum variations. A subsequent paper will compare observations with this model, in a search for the effects of spatial coherence invoked by many theories of pulsar emission
Zhelyazkova, V
2015-01-01
Dipole-dipole interactions between helium atoms in Rydberg-Stark states with principal quantum number $n=53$ and approximately linear Stark energy shifts, resulting from induced electric dipole moments of approximately 7900 D, have been investigated experimentally. The experiments were performed in pulsed supersonic metastable helium beams, with particle number densities of up to $\\sim10^9$ cm$^{-3}$. In the presence of amplitude-modulated, radio-frequency electric fields, changes in the spectral intensity distributions associated with the transitions to these states that are attributed to dipole-dipole interactions within the ensembles of excited atoms have been observed. The experimental results are in excellent agreement with calculations of the Rydberg energy level structure carried out using Floquet methods, and excitations shared by up to 4 atoms. The use of these Rydberg-Stark states as sensors for non-resonant broadband radio-frequency electrical noise is also discussed.
Shaping symmetric Airy beam through binary amplitude modulation for ultralong needle focus
Fang, Zhao-Xiang; Gong, Lei; Vaveliuk, Pablo; Chen, Yue; Lu, Rong-De
2015-01-01
Needle-like electromagnetic fields has various advantages for the applications in high-resolution imaging, Raman Spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device(DMD). Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional(1D) and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We...
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.
Otte, E.; Schlickriede, C.; Alpmann, C.; Denz, C.
2015-03-01
We present a method to tailor not only amplitude and phase of a complex light field, but also the transverse states of polarization. Starting from the implementation of spatially inhomogeneous distributions of polarization, so called Poincaré beams, we realized a holographic optical technique that allows arbitrarily modulating the states of polarization by a single phase-only spatial light modulator (SLM). Moreover, the effective amplitude modulation of higher order beams performed by a phase-only SLM is shown. We will demonstrate the capabilities of our method ranging from the modulation of higher order Gaussian modes including desired polarization characteristics to the generation of polarization singularities at arbitrary points in the transverse plane of Poincaré beams.
Schreiner, C E; Urbas, J V
1986-01-01
The ability of cortical neurons to follow amplitude modulation (AM) of tones was examined in the anterior auditory cortical field (AAF) of anesthetized cats using multiple-unit recording techniques. Sinusoidal and rectangular modulations (100%) of a monaural carrier tone at the characteristic frequency of each location were presented to study the degree of response synchronization and changes in firing rate as a function of the modulation frequency. All investigated locations were tuned to a 'best modulation frequency' (BMF) as determined by synchronization measures. Almost all locations (94%) were tuned to a BMF as determined by spike rate. Maximal binaural-interaction strength was observed for modulation frequencies close to the BMF of neurons. For sinusoidal AM, a correlation (r = 0.63, P less than 0.01) between BMF and CF of neurons in AAF could be demonstrated for the synchronization of the response. PMID:3013823
International Nuclear Information System (INIS)
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. (paper)
Hüser, Dorothee; Häßler-Grohne, Wolfgang; Hüser, Jonathan
2013-11-01
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.
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
2015-01-01
Rationale Previous cochlear implant (CI) studies have shown that single-channel amplitude modulation frequency discrimination (AMFD) can be improved when coherent modulation is delivered to additional channels. It is unclear whether the multi-channel advantage is due to increased loudness, multiple envelope representations, or to component channels with better temporal processing. Measuring envelope interference may shed light on how modulated channels can be combined. Methods In this study, multi-channel AMFD was measured in CI subjects using a 3-alternative forced-choice, non-adaptive procedure (“which interval is different?”). For the reference stimulus, the reference AM (100 Hz) was delivered to all 3 channels. For the probe stimulus, the target AM (101, 102, 104, 108, 116, 132, 164, 228, or 256 Hz) was delivered to 1 of 3 channels, and the reference AM (100 Hz) delivered to the other 2 channels. The spacing between electrodes was varied to be wide or narrow to test different degrees of channel interaction. Results Results showed that CI subjects were highly sensitive to interactions between the reference and target envelopes. However, performance was non-monotonic as a function of target AM frequency. For the wide spacing, there was significantly less envelope interaction when the target AM was delivered to the basal channel. For the narrow spacing, there was no effect of target AM channel. The present data were also compared to a related previous study in which the target AM was delivered to a single channel or to all 3 channels. AMFD was much better with multiple than with single channels whether the target AM was delivered to 1 of 3 or to all 3 channels. For very small differences between the reference and target AM frequencies (2–4 Hz), there was often greater sensitivity when the target AM was delivered to 1 of 3 channels versus all 3 channels, especially for narrowly spaced electrodes. Conclusions Besides the increased loudness, the present results also suggest that multiple envelope representations may contribute to the multi-channel advantage observed in previous AMFD studies. The different patterns of results for the wide and narrow spacing suggest a peripheral contribution to multi-channel temporal processing. Because the effect of target AM frequency was non-monotonic in this study, adaptive procedures may not be suitable to measure AMFD thresholds with interfering envelopes. Envelope interactions among multiple channels may be quite complex, depending on the envelope information presented to each channel and the relative independence of the stimulated channels. PMID:26431043
Axial Flows in Kármán Vortices Due to Amplitude Modulation and a Free Surface
Voorhees, A.; Benaroya, H.; Wei, T.
2000-11-01
Fluid-structure interaction experiments were conducted in a large free-surface water tunnel facility using a low-mass ratio circular cylinder. The 2.54-cm cylinder was attached at the lower end to the tunnel floor by a leaf spring and the upper end protruded through the free surface. In this manner, the cylinder was free to oscillate as an inverted pendulum in response to the Kármán vortex shedding phenomenon. Far from the free-surface, strong axial flows directed toward the free-surface were observed along the cores of Kármán vortices shed from the oscillating cylinder; such flows were not observed for matched Reynolds number flows where the cylinder was held stationary. However, near the free-surface fluid motion along vortex cores traveled both up and down, i.e. to and from the free-surface. It has been found that this phenomenon is directly linked to an observed beating of the cylinder when the oscillation frequency approaches the cylinder's natural frequency. In this study, the Reynolds number based on cylinder diameter and free stream velocity was 3800. The problem to be discussed is that of the interaction between the amplitude modulated cylinder motion, the ensuing vortex-street, and the free-surface. These interactions will be described using DPIV measurements taken over a range of levels beneath the free-surface. A phenomenological description of the axial vortex induction process will be developed using Kármán vortex strength as a function of distance from the free-surface.
Acuña, Alonso M; Snellenburg, Joris J; Gwizdala, Michal; Kirilovsky, Diana; van Grondelle, Rienk; van Stokkum, Ivo H M
2016-01-01
Pulse-amplitude modulated (PAM) fluorometry is extensively used to characterize photosynthetic organisms on the slow time-scale (1-1000 s). The saturation pulse method allows determination of the quantum yields of maximal (F M) and minimal fluorescence (F 0), parameters related to the activity of the photosynthetic apparatus. Also, when the sample undergoes a certain light treatment during the measurement, the fluorescence quantum yields of the unquenched and the quenched states can be determined. In the case of cyanobacteria, however, the recorded fluorescence does not exclusively stem from the chlorophyll a in photosystem II (PSII). The phycobilins, the pigments of the cyanobacterial light-harvesting complexes, the phycobilisomes (PB), also contribute to the PAM signal, and therefore, F 0 and F M are no longer related to PSII only. We present a functional model that takes into account the presence of several fluorescent species whose concentrations can be resolved provided their fluorescence quantum yields are known. Data analysis of PAM measurements on in vivo cells of our model organism Synechocystis PCC6803 is discussed. Three different components are found necessary to fit the data: uncoupled PB (PBfree), PB-PSII complexes, and free PSI. The free PSII contribution was negligible. The PBfree contribution substantially increased in the mutants that lack the core terminal emitter subunits allophycocyanin D or allophycocyanin F. A positive correlation was found between the amount of PBfree and the rate constants describing the binding of the activated orange carotenoid protein to PB, responsible for non-photochemical quenching. PMID:25893897
Borisov, Vladimir; Veniaminov, Andrey
2015-10-01
Amplitude and phase contributions to mixed volume holographic gratings were extracted from measured contours of angular selectivity. Holograms for the investigation were recorded in the glassy polymer material with phenan-threnequinone (PQ) using the DPSS CW laser (532 nm) and then self-developed due to molecular diffusion of PQ, reaching diffraction efficiency about 40%. Refractive index and absorbance modulation amplitudes of those holograms were obtained as adjustable parameters from theoretical equations by fitting angular dependencies of zeros and 1st orders diffraction efficiency measured at 450, 473, 532, and 633 nm at the different stages of hologram development. Mixed gratings manifest themselves in asymmetrical transmittance selectivity contours with one minimum and one maximum shifted with respect to the Bragg angle, while symmetrical contours with a minimum or a maximum at the Bragg angle are characteristic of pure phase and amplitude gratings, respectively. In the course of a hologram development, it converts from a predominantly amplitude-mixed to almost purely phase one in the case of readout using a light within the absorption band of PQ and maintains the phase nature besides it. The value of refractive index amplitude is ranging from 5×10-6 to 10-4 and the value of absorbance amplitude is up to 140 m-1.
Bourget, P.; Mawet, D.; Mardones, P.; Schuhler, N.; Pueyo, L.; Girard, J.; Haguenauer, P.; Gonte, F.
2013-09-01
We present a new Adaptive Phase Mask (APM) coronagraph design enabling Amplitude and Phase Modulation control (APM). The Adaptive Phase mask coronagraph is a technique proposed to provide both high dynamic and high angular resolution imaging of faint sources around bright objects. Discriminating faint sources from static speckles is a challenging problem. Our new system is based on synchronous demodulation that allows high dynamic range detection of a faint target immersed in a background. The APM2 uses the coherence of speckles to discriminate them from proper companions, using the mask itself as the electric field modulator. Synchronous detection in the radio frequency range is used to side-step the effect of atmospheric turbulence and enable the detection of low amplitude signals. The APM2 concept offers high dynamic range detection and provides a time- and cost-effective method to quantify the probability of presence of a faint object close to the central star.
Czech Academy of Sciences Publication Activity Database
Mat?jka, M.; Pick, P.; Popelka, Lukáš; Šimurda, David
Edinburg : Otimage Ltd., 2010 - (Grant, I.), s. 1-5 ISBN 978-0-9565333-0-2. [ICAS 2010 /27./. Nice (FR), 19.09.2010-24.09.2010] R&D Projects: GA MŠk(CZ) 1M06031; GA AV ?R IAA2076403; GA ?R GA101/08/1112 Institutional research plan: CEZ:AV0Z20760514 Keywords : synthetic jet actuator * wake * amplitude modulation Subject RIV: BK - Fluid Dynamics
Pyragas, Kestutis; Novi?enko, Viktor
2015-01-01
The phase reduction method for a limit cycle oscillator subjected to a strong amplitude-modulated high-frequency force is developed. An equation for the phase dynamics is derived by introducing a new, effective phase response curve. We show that if the effective phase response curve is everywhere positive (negative), then an entrainment of the oscillator to an envelope frequency is possible only when this frequency is higher (lower) than the natural frequency of the oscillat...
International Nuclear Information System (INIS)
A single-mode laser noise model driven by quadratic colored pump noise and biased amplitude modulation signal is proposed. The analytic expression of signal-to-noise ratio is calculated by using a new linearized procedure. It is found that there are three different typies of stochastic resonance in the model: the conventional form of stochastic resonance, the stochastic resonance in the broad sense, and the bona fide SR.
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.
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.
International Nuclear Information System (INIS)
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 F0/Fv. 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?q/F?m, EC50 = 303 ± 64 ?g U L?1 after 5 h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC50 = 142 ± 98 ?g U L?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
High-precision laser beam shaping using a binary-amplitude spatial light modulator.
Liang, Jinyang; Kohn, Rudolph N; Becker, Michael F; Heinzen, Daniel J
2010-03-10
We have achieved high-precision laser beam shaping by using a binary-amplitude spatial light modulator, a digital micromirror device (DMD), followed by an imaging telescope that contains a pinhole low-pass filter (LPF). An error diffusion algorithm was used to design the initial DMD pixel pattern based on the measured input beam profile. This pattern was iteratively refined by simulating the optically low-pass filtered DMD image and changing DMD pixels to lift valleys and suppress peaks. We noted the gap between the experimental result of 1.4% root-mean-square (RMS) error and the simulated result for the same DMD pattern of 0.3% RMS error. Therefore, we deemed it necessary to introduce iterative refinement based on actual measurements of the output image to further improve the uniformity of the beam. Using this method, we have demonstrated the ability to shape raw, non-spatially filtered laser beams (quasi-Gaussian beams) into beams with precisely controlled profiles that have an unprecedented level of RMS error with respect to the target profile. We have shown that our iterative refinement process is able to improve the light intensity uniformity to around 1% RMS error in a raw camera image for both 633 and 1064 nm laser beams. The use of a digital LPF on the camera image is justified in that it matches the performance of the pinhole filter in the experimental setup. The digital low-pass filtered results reveal that the actual optical beam profiles have RMS error down to 0.23%. Our approach has also demonstrated the ability to produce a range of target profiles as long as they have similar spatial-frequency content (i.e., a slowly varying beam profile). Circular and square cross-section flat-top beams and beams with a linear intensity variation within a circular and square cross section were produced with similarly low RMS errors. The measured errors were about twice the ultimate limit of 0.1% RMS error based on the number of binary DMD pixels that participate in the beam-formation process. PMID:20220887
DEFF Research Database (Denmark)
Pallesen, Karen Johanne; Bailey, Christopher J
2015-01-01
Musical expertise is associated with structural and functional changes in the brain that underlie facilitated auditory perception. We investigated whether the phase locking (PL) and amplitude modulations (AM) of neuronal oscillations in response to musical chords are correlated with musical expertise and whether they reflect the prototypicality of chords in Western tonal music. To this aim, we recorded magnetoencephalography (MEG) while musicians and non-musicians were presented with common prototypical major and minor chords, and with uncommon, non-prototypical dissonant and mistuned chords, while watching a silenced movie. We then analyzed the PL and AM of ongoing oscillations in the theta (4-8 Hz) alpha (8-14 Hz), beta- (14-30 Hz) and gamma- (30-80 Hz) bands to these chords. We found that musical expertise was associated with strengthened PL of ongoing oscillations to chords over a wide frequency range during the first 300 ms from stimulus onset, as opposed to increased alpha-band AM to chords over temporal MEG channels. In musicians, the gamma-band PL was strongest to non-prototypical compared to other chords, while in non-musicians PL was strongest to minor chords. In both musicians and non-musicians the long-latency (> 200 ms) gamma-band PL was also sensitive to chord identity, and particularly to the amplitude modulations (beats) of the dissonant chord. These findings suggest that musical expertise modulates oscillation PL to musical chords and that the strength of these modulations is dependent on chord prototypicality.
Lechinger, Julia; Heib, Dominik Philip Johannes; Gruber, Walter; Schabus, Manuel; Klimesch, Wolfgang
2015-11-01
Based on physiological models of neurovisceral integration, different studies have shown how cognitive processes modulate heart rate and how the heartbeat, on the other hand, modulates brain activity. We tried to further determine interactions between cardiac and electrical brain activity by means of EEG. We investigated how the heartbeat modulates EEG in 23 healthy controls from wakefulness to deep sleep and showed that frontocentral heartbeat evoked EEG amplitude and phase locking (as measured by intertrial phase locking), at about 300-400 ms after the R peak, decreased with increasing sleep depth with a renewed increase during REM sleep, which underpins the assumption that the heartbeat evoked positivity constitutes an active frontocortical response to the heartbeat. Additionally, we found that individual heart rate was correlated with the frequency of the EEG's spectral peak (i.e., alpha peak frequency during wakefulness). This correlation was strongest during wakefulness and declined linearly with increasing sleep depth. Furthermore, we show that the QRS complex modulates spindle phase possibly related to the correspondence between the frequency of the QRS complex and the spindle frequency of about 12-15 Hz. Finally, during deep sleep stages, a loose temporal coupling between heartbeats and slow oscillation (0.8 Hz) could be observed. These findings indicate that cardiac activity such as heart rate or individual heartbeats can modulate or be modulated by ongoing oscillatory brain activity. PMID:26268858
Zhang, Qiushi; Zhao, Xiaojie; Zhu, Chaozhe; Yang, Xueqian; Yao, Li
2015-03-01
The functional magnetic resonance imaging (fMRI) researches on working memory have found that activation of cortical areas appeared dependent on memory load, and event-related potentials (ERP) studies have demonstrated that amplitudes of P300 decreased significantly when working memory load increased. However, the cortical activities related with P300 amplitudes under different memory loads remains unclear. Joint fMRI and EEG analysis which fusions the time and spatial information in simultaneous EEG-fMRI recording can reveal the regional activation at each ERP time point. In this paper, we first used wavelet transform to obtain the single-trial amplitudes of P300 caused by a digital N-back task in the simultaneous EEG-fMRI recording as the ERP feature sequences. Then the feature sequences in 1-back condition and 3-back condition were introduced into general linear model (GLM) separately as parametric modulations to compare the cortical activation under different memory loads. The results showed that the average amplitudes of P300 in 3-back significantly decreased than that in 1-back, and the activities induced by ERP feature sequences in 3-back also significantly decreased than that in the 1-back, including the insular, anterior cingulate cortex, right inferior frontal gyrus, and medial frontal gyrus, which were relevant to the storage, monitoring, and manipulation of information in working memory task. Moreover, the difference in the activation caused by ERP feature showed a positive correlation with the difference in behavioral performance. These findings demonstrated the locations of P300 amplitudes differences modulated by the memory load and its relationship with the behavioral performance.
The onion fly modulates the adult eclosion time in response to amplitude of temperature cycle
Tanaka, Kazuhiro; Watari, Yasuhiko
2011-08-01
To confirm whether the amplitude of diel temperature cycles causes a phase shift of adult eclosion rhythm of the onion fly, Delia antiqua, the peak time ( Ø E) of adult eclosion was determined under various thermoperiods with a fixed temperature either in the warm or cool phase and temperature differences ranging from 1°C to 4°C between the two phases. Irrespective of the temperature level during the warm or cool phase, Ø E occurred earlier with decreasing amplitude of the temperature cycle. The results strongly support the previous conclusion of Tanaka and Watari (Naturwissenschaften 90:76-79, 2003) that D. antiqua responds to the amplitude of temperature cycle as a cue for the circadian adult eclosion timing. The phase advance was larger in thermoperiods with a fixed warm-phase temperature than in those with a fixed cool-phase temperature. This might be ascribed to the interaction between the amplitude and level of temperature in the thermoperiodic regimes.
Triggerable electro-optic amplitude modulator bias stabilizer for integrated optical devices
Conder, Alan D. (Tracy, CA); Haigh, Ronald E. (Tracy, CA); Hugenberg, Keith F. (Livermore, CA)
1995-01-01
An improved Mach-Zehnder integrated optical electro-optic modulator is achieved by application and incorporation of a DC bias box containing a laser synchronized trigger circuit, a DC ramp and hold circuit, a modulator transfer function negative peak detector circuit, and an adjustable delay circuit. The DC bias box ramps the DC bias along the transfer function curve to any desired phase or point of operation at which point the RF modulation takes place.
Energy Technology Data Exchange (ETDEWEB)
Elekes, E.; Thuroczy, G.; Szabo, L.D. [National Frederic Joliot-Curie Research Inst. for Radiobiology and Radiohygiene, Budapest (Hungary)
1996-12-01
The effect of continuous (CW; 2.45 GHz carrier frequency) or amplitude-modulated (AM; 50 Hz square wave) microwave radiation on the immune response was tested. CW exposures (6 days, 3 h/day) induced elevations of the number of antibody-producing cells in the spleen of male Balb/c mice (+37%). AM microwave exposure induced elevation of the spleen index (+15%) and antibody-producing cell number (+55%) in the spleen of male mice. No changes were observed in female mice. It is concluded that both types of exposure conditions induced moderate elevation of antibody production only in male mice.
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
Pfabigan, Daniela M.; Zeiler, Michael; Lamm, Claus; Sailer, Uta
2014-01-01
•ERP responses to feedback stimuli with explicit or assigned valence information were investigated with blocked or randomized trial presentation modes.•Only P3b, but not feedback-related negativity amplitudes were affected by feedback type for both presentation modes.•Results suggest using blocked design when using different types of feedback stimuli.
Energy Technology Data Exchange (ETDEWEB)
Hoegger, B.A.; Schneider, H.; Vaucher, B.G. (Fribourg Univ. (Switzerland). Inst. de Physique)
1982-06-30
Magnetoacoustic oscillations are excited in an inhomogeneous magnetized plasma cylinder by amplitude modulation of a high frequency field (2.45 GHz, 3 kW PEP). The antenna is a long helical slow-wave structure. The axial field-oscillating with the modulation frequency (2/15 MHz) is monitored by means of electrostatically shielded magnetic probes. Resonance behaviour is observed around the eigenfrequency of the plasma cylinder. Power absorption is measured with diamagnetic loop technique. The plasma parameters are: mean electron density 3x10/sup 12/ cm/sup -3/, electron temperature 3.5 eV, magnetic field 1.6 kG, filling gas 7x10/sup -4/ Torr argon.
Directory of Open Access Journals (Sweden)
Francucci M
2010-01-01
Full Text Available Amplitude-modulated (AM laser imaging is a promising technology for the production of accurate three-dimensional (3D images of submerged scenes. The main challenge is that radiation scattered off water gives rise to a disturbing signal (optical noise that degrades more and more the quality of 3D images for increasing turbidity. In this paper, we summarize a series of theoretical findings, that provide valuable hints for the development of experimental methods enabling a partial rejection of optical noise in underwater imaging systems. In order to assess the effectiveness of these methods, which range from modulation/demodulation to polarimetry, we carried out a series of experiments by using the laboratory prototype of an AM 3D imager ( = 405?nm for marine archaeology surveys, in course of realization at the ENEA Artificial Vision Laboratory (Frascati, Rome. The obtained results confirm the validity of the proposed methods for optical noise rejection.
DEFF Research Database (Denmark)
Isaeva, Olga B.; Kuznetsov, Sergey P.; Mosekilde, Erik
2011-01-01
The paper proposes an approach to constructing feasible examples of dynamical systems with hyperbolic chaotic attractors based on the successive transfer of excitation between two pairs of self-oscillators that are alternately active. An angular variable that measures the relations of the current 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 i...
Phase dependent modulation of tremor amplitude in essential tremor through thalamic stimulation.
Cagnan, H; Brittain, JS; Little, S.; Foltynie, T; Limousin, P.; Zrinzo, L.; Hariz, M; Joint, C; FitzGerald, J; Green, AL; Aziz, T.; Brown, P.
2013-01-01
High frequency deep brain stimulation of the thalamus can help ameliorate severe essential tremor. Here we explore how the efficacy, efficiency and selectivity of thalamic deep brain stimulation might be improved in this condition. We started from the hypothesis that the effects of electrical stimulation on essential tremor may be phase dependent, and that, in particular, there are tremor phases at which stimuli preferentially lead to a reduction in the amplitude of tremor. The latter could b...
Improvement of the Spatial Amplitude Isotropy of a 4He Magnetometer Using a Modulated Pumping Beam
Chéron, B.; Gilles, H; Hamel, J.; Moreau, O; Noël, E.
1997-01-01
Optically pumped magnetometers are scalar magnetometers. Contrary to vectoriel magnetometers, they measure the total magnetic field whatever the direction of the sensor. However, for some orientations of the magnetometer with respect to the magnetic field direction, the resonant signal vanishes and the measurement is impossible. In this paper we present a simple solution to reduce the amplitude spatial anisotropy and apply it to a 4He magnetometer developed in our Laboratory.
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.
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.
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.
Scanning tunneling microscopy in TTF-TCNQ: Phase and amplitude modulated charge density waves
DEFF Research Database (Denmark)
Wang, Z.Z.; Gorard, J.C.
2003-01-01
Charge density waves (CDWs) have been studied at the surface of a cleaved tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) single crystal using a low temperature scanning tunneling microscope (STM) under ultrahigh-vacuum conditions, between 300 and 33 K with molecular resolution. All CDW phase transitions of TTF-TCNQ have been identified. The measurement of the modulation wave vector along the a direction provides evidence of the existence of domains comprising single plane wave modulated structures in the temperature regime where the transverse wave vector of the CDW is temperature dependent, as hinted by the theory more than 20 years ago.
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.
Phase-amplitude coupling characteristics in directly modulated quantum dot lasers
International Nuclear Information System (INIS)
We present a semi-analytical model for studying the phase-amplitude coupling (?-factor) in quantum dot (QD) semiconductor lasers, which takes into account the influence of carrier populations in the excited state and in the two-dimensional carrier reservoir on the refractive index change. Calculations of the ?-factor based on the amplified spontaneous emission method and on the “FM/AM” technique are both investigated. It is shown that the ?-factor of a QD laser strongly depends on the energy separation between the ground state and the off-resonant states. Through band structure engineering, the ?-factor can be reduced by enlarging this energy separation
Phase-amplitude coupling characteristics in directly modulated quantum dot lasers
Energy Technology Data Exchange (ETDEWEB)
Wang, C. [Télécom ParisTech, Ecole Nationale Supérieure des Télécommunications, CNRS LTCI, 75634 Paris Cedex 13 (France); Institut National des Sciences Appliquées, Université Européenne de Bretagne, 35708 Rennes Cedex 7 (France); Osi?ski, M. [Télécom ParisTech, Ecole Nationale Supérieure des Télécommunications, CNRS LTCI, 75634 Paris Cedex 13 (France); Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106-4343 (United States); Even, J. [Institut National des Sciences Appliquées, Université Européenne de Bretagne, 35708 Rennes Cedex 7 (France); Grillot, F. [Télécom ParisTech, Ecole Nationale Supérieure des Télécommunications, CNRS LTCI, 75634 Paris Cedex 13 (France)
2014-12-01
We present a semi-analytical model for studying the phase-amplitude coupling (?-factor) in quantum dot (QD) semiconductor lasers, which takes into account the influence of carrier populations in the excited state and in the two-dimensional carrier reservoir on the refractive index change. Calculations of the ?-factor based on the amplified spontaneous emission method and on the “FM/AM” technique are both investigated. It is shown that the ?-factor of a QD laser strongly depends on the energy separation between the ground state and the off-resonant states. Through band structure engineering, the ?-factor can be reduced by enlarging this energy separation.
Amplitude modulation for the Swift-Hohenberg and Kuramoto-Sivashinski equations
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.
International Nuclear Information System (INIS)
Past theoretical and numerical studies of the nonlinear evolution of electromagnetic cyclotron waves are reviewed. Such waves are commonly observed in space plasmas such as Alfven waves in the solar wind or VLF whistler mode waves in the magnetosphere. The use of an electromagnetic full-particle code to study an electron cyclotron wave and of an electromagnetic hybrid code to study an ion cyclotron wave is demonstrated. Recent achievements in the simulations of nonlinear revolution of electromagnetic cyclotron waves are discussed. The inverse cascading processes of finite-amplitude whistler and Alfven waves is interpreted in terms of physical elementary processes. 65 refs
International Nuclear Information System (INIS)
Residual stress modulation in the diamond-like carbon coatings with incorporation of gold nanoparticles was studied critically. The films were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma chemical vapor deposition. Stresses in the films were determined from the broadening of the optical absorption tail and were found to decrease from 2.3 GPa to 0.48 GPa with increasing gold content (2-7 at.% Au) in the DLC matrix. Gold incorporation also made the films harder than the corresponding DLC coatings. Modulation of stress with nanocrystalline gold content in the DLC matrix was related to the relative amount of sp2/sp3 content in the DLC films.
Energy Technology Data Exchange (ETDEWEB)
Paul, R.; Bhattacharyya, S.R.; Bhar, R. [Department of Instrumentation Science, USIC Building, Jadavpur University, Kolkata 700032 (India); Pal, A.K., E-mail: msakp2002@yahoo.co.in [Department of Instrumentation Science, USIC Building, Jadavpur University, Kolkata 700032 (India)
2011-10-01
Residual stress modulation in the diamond-like carbon coatings with incorporation of gold nanoparticles was studied critically. The films were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma chemical vapor deposition. Stresses in the films were determined from the broadening of the optical absorption tail and were found to decrease from 2.3 GPa to 0.48 GPa with increasing gold content (2-7 at.% Au) in the DLC matrix. Gold incorporation also made the films harder than the corresponding DLC coatings. Modulation of stress with nanocrystalline gold content in the DLC matrix was related to the relative amount of sp{sup 2}/sp{sup 3} content in the DLC films.
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. PMID:16605661
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...
Guéguin, Marie; Le Bouquin-Jeannès, Régine; Faucon, Gérard; Chauvel, Patrick; Liégeois-Chauvel, Catherine
2007-02-01
The human auditory cortex includes several interconnected areas. A better understanding of the mechanisms involved in auditory cortical functions requires a detailed knowledge of neuronal connectivity between functional cortical regions. In human, it is difficult to track in vivo neuronal connectivity. We investigated the interarea connection in vivo in the auditory cortex using a method of directed coherence (DCOH) applied to depth auditory evoked potentials (AEPs). This paper presents simultaneous AEPs recordings from insular gyrus (IG), primary and secondary cortices (Heschl's gyrus and planum temporale), and associative areas (Brodmann area [BA] 22) with multilead intracerebral electrodes in response to sinusoidal modulated white noises in 4 epileptic patients who underwent invasive monitoring with depth electrodes for epilepsy surgery. DCOH allowed estimation of the causality between 2 signals recorded from different cortical sites. The results showed 1) a predominant auditory stream within the primary auditory cortex from the most medial region to the most lateral one whatever the modulation frequency, 2) unidirectional functional connection from the primary to secondary auditory cortex, 3) a major auditory propagation from the posterior areas to the anterior ones, particularly at 8, 16, and 32 Hz, and 4) a particular role of Heschl's sulcus dispatching information to the different auditory areas. These findings suggest that cortical processing of auditory information is performed in serial and parallel streams. Our data showed that the auditory propagation could not be associated to a unidirectional traveling wave but to a constant interaction between these areas that could reflect the large adaptive and plastic capacities of auditory cortex. The role of the IG is discussed. PMID:16514106
Scientific Electronic Library Online (English)
Danielle Gomes, Pinto; Silvana Maria Sobral, Griz; Otávio Gomes, Lins.
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 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.
Gorecki, Christophe; Trolard, Bertrand; Oriat, Luc
1996-05-01
We have built an optical VanderLugt-type correlator that uses two Epson liquid crystal televisions (LCTVs) separately generating the amplitude and phase modulation properties. The input scene is displayed in amplitudemostly regime on the first LCTV. Thereafter a phase-only filter with a different level of phase quantization is addressed in phase-mostly regime on the second LCTV. To characterize this device, the phase and amplitude modulations were experimentally measured and investigated in pattern recognition application where the grey-level input scenes and multilevel kinoforms are displayed on the LCTVs.
Kifle, Muli; Vanderaar, Mark
1994-02-01
Union bounds and Monte Carlo simulation Bit-Error-Rate (BER) performance results are presented for various 32-ary and 64-ary Quadrature Amplitude Modulation (QAM) schemes. Filtered and unfiltered modulation formats are compared for the best packing arrangement in peak power limited systems. It is verified that circular constellations which populate as many symbols as possible at the peak magnitude offer the best performance. For example: a 32-ary QAM scheme based on concentric circles offers about 1.05 dB better peak power improvement at a BER of 10(exp -6) over the scheme optimized for average power using triangular symbol packing. This peak power improvement increases to 1.25 dB for comparable 64-ary QAM schemes. This work serves as a precursor to determine the feasibility of a combined modem/codec that can accommodate Broadband Integrated Services Digital Network (B-ISDN) at a rate of 155.52 Mbps through typical transponder bandwidths of 36 MHz and 54 MHz.
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
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.
International Nuclear Information System (INIS)
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. (paper)
Tao, Li; Wang, Yiguang; Gao, Yuliang; Lau, Alan Pak Tao; Chi, Nan; Lu, Chao
2013-03-11
Carrier-less amplitude and phase (CAP) modulation can be a good candidate for short range optical communications for considerable computational complexity reduction and simple system structure. In this paper, a detailed investigation on the digital filters in CAP modulation system is presented. An adaptive equalizer based on cascaded multi-modulus algorithm (CMMA) is used for the demodulation at the receiver. The impact of digital filter taps on system performance is investigated through comprehensive simulations and a 10 Gb/s CAP16 modulation system is demonstrated experimentally. The BER performance for different length of fiber link is measured. Compared with back-to-back (BTB) transmissions, 2 dB and 3.5 dB receiver power penalty are observed at BER of 10(-3) for 20 km and 40 km fiber link respectively. It clearly demonstrates the feasibility of the CAP16 modulation for the short range transmission systems. PMID:23482215
Directory of Open Access Journals (Sweden)
A. Bali?ski
2013-01-01
Full Text Available Describes how to obtain a soluble sodium silicate with a density of 1.40 g/cm3, 1.45 g/cm3, 1.50 g/cm3, and silica module M = 2.1obtained from the silica- sodium glass with module M = 3.3 and M = 2.1. Residual (final strength of molding samples made with thesebinders, were determined at temperatures corresponding to the characteristic temperatures of phase and temperature transitions of silica gel. Indicated the type of soluble sodium silicate capable of obtain the smallest value of the final strength of molding sand in the specified range of temperatures.
A. Bali?ski
2013-01-01
Describes how to obtain a soluble sodium silicate with a density of 1.40 g/cm3, 1.45 g/cm3, 1.50 g/cm3, and silica module M = 2.1obtained from the silica- sodium glass with module M = 3.3 and M = 2.1. Residual (final) strength of molding samples made with thesebinders, were determined at temperatures corresponding to the characteristic temperatures of phase and temperature transitions of silica gel. Indicated the type of soluble sodium silicate capable of obtain the smallest value of the fina...
Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769
Aerts, C.; Simón-Díaz, S.; Catala, C.; Neiner, C.; Briquet, M.; Castro, N.; Schmid, V. S.; Scardia, M.; Rainer, M.; Poretti, E.; Pápics, P. I.; Degroote, P.; Bloemen, S.; Østensen, R. H.; Auvergne, M.; Baglin, A.; Baudin, F.; Michel, E.; Samadi, R.
2013-09-01
Aims: 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. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data 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, assuming a dipole field. Results: 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 reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6 m telescope, under programme LP185.D-0056. Based on observations obtained with the HERMES spectrograph attached to the 1.2 m Mercator telescope, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientific (FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland, and the Thüringer Landessternwarte Tautenburg, Germany. Based on observations obtained with the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU).
Ser and Thr residues modulate the conformation of pro-kinked transmembrane alpha-helices.
Deupi, Xavier; Olivella, Mireia; Govaerts, Cedric; Ballesteros, Juan Antonio; Campillo, Mercedes; Pardo, Leonardo
2004-01-01
Functionally required conformational plasticity of transmembrane proteins implies that specific structural motifs have been integrated in transmembrane helices. Surveying a database of transmembrane helices and the large family of G-protein coupled receptors we identified a series of overrepresented motifs associating Pro with either Ser or Thr. Thus, we have studied the conformation of Pro-kinked transmembrane helices containing Ser or Thr residues, in both g+ and g- rotamers, by molecular dynamics simulations in a hydrophobic environment. Analysis of the simulations shows that Ser or Thr can significantly modulate the deformation of the Pro. A series of motifs, such as (S/T)P and (S/T)AP in the g+ rotamer and the TAP and PAA(S/T) motifs in the g- rotamer, induce an increase in bending angle of the helix compared to a standard Pro-kink, apparently due to the additional hydrogen bond formed between the side chain of Ser/Thr and the backbone carbonyl oxygen. In contrast, (S/T)AAP and PA(S/T) motifs, in both g+ and g-, and PAA(S/T) in g+ rotamers decrease the bending angle of the helix by either reducing the steric clash between the pyrrolidine ring of Pro and the helical backbone, or by adding a constrain in the form of a hydrogen bond in the curved-in face of the helix. Together with a number of available experimental data, our results strongly suggest that association of Ser and Thr with Pro is commonly used in transmembrane helices to accommodate the structural needs of specific functions. PMID:14695254
Ser and Thr Residues Modulate the Conformation of Pro-Kinked Transmembrane ?-Helices
Deupi, Xavier; Olivella, Mireia; Govaerts, Cedric; Ballesteros, Juan Antonio; Campillo, Mercedes; Pardo, Leonardo
2004-01-01
Functionally required conformational plasticity of transmembrane proteins implies that specific structural motifs have been integrated in transmembrane helices. Surveying a database of transmembrane helices and the large family of G-protein coupled receptors we identified a series of overrepresented motifs associating Pro with either Ser or Thr. Thus, we have studied the conformation of Pro-kinked transmembrane helices containing Ser or Thr residues, in both g+ and g? rotamers, by molecular dynamics simulations in a hydrophobic environment. Analysis of the simulations shows that Ser or Thr can significantly modulate the deformation of the Pro. A series of motifs, such as (S/T)P and (S/T)AP in the g+ rotamer and the TAP and PAA(S/T) motifs in the g? rotamer, induce an increase in bending angle of the helix compared to a standard Pro-kink, apparently due to the additional hydrogen bond formed between the side chain of Ser/Thr and the backbone carbonyl oxygen. In contrast, (S/T)AAP and PA(S/T) motifs, in both g+ and g?, and PAA(S/T) in g+ rotamers decrease the bending angle of the helix by either reducing the steric clash between the pyrrolidine ring of Pro and the helical backbone, or by adding a constrain in the form of a hydrogen bond in the curved-in face of the helix. Together with a number of available experimental data, our results strongly suggest that association of Ser and Thr with Pro is commonly used in transmembrane helices to accommodate the structural needs of specific functions. PMID:14695254
Burgmeier, Jörg; Waltermann, Christian; Flachenecker, Günter; Schade, Wolfgang
2014-02-01
Femtosecond laser pulses were used for the direct point-by-point inscription of phase-shifted fiber Bragg gratings (FBGs) in a single fabrication step without postprocessing. An electro-optic amplitude modulator is used in the setup to generate a defined delay between two identical laser pulse trains for the grating inscription. The grating structure with a central phase shift is formed by focusing the modulated laser pulses into the core of a fiber, while the fiber is translated with a constant velocity. The induced phase shift leads to a narrow transmission band with a bandwidth considerably below 10 pm within the stop band of the FBG. The inscribed FBGs show a birefringence of 3.9×10(-5) whereas their temperature and strain sensitivities are 10.4??pm/K and 1.4??pm/?strain, respectively. The fabrication process is fast and offers a high grade of flexibility for the control of all grating parameters. PMID:24487860
Neuropathic and inflammatory pain are modulated by tuberoinfundibular peptide of 39 residues
Dimitrov, Eugene L.; Kuo, Jonathan; Kohno, Kenji; Usdin, Ted B.
2013-01-01
Nociceptive information is modulated by a large number of endogenous signaling agents that change over the course of recovery from injury. This plasticity makes understanding regulatory mechanisms involved in descending inhibition of pain scientifically and clinically important. Neurons that synthesize the neuropeptide TIP39 project to many areas that modulate nociceptive information. These areas are enriched in its receptor, the parathyroid hormone 2 receptor (PTH2R). We previously found tha...
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.
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.
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
Self-similarities in the frequency-amplitude space of a loss-modulated CO$_2$ laser
Bonatto, Cristian; Garreau, Jean Claude; Gallas, Jason A. C.
2005-01-01
We show the standard two-level continuous-time model of loss-modulated CO$_2$ lasers to display the same regular network of self-similar stability islands known so far to be typically present only in discrete-time models based on mappings. For class B laser models our results suggest that, more than just convenient surrogates, discrete mappings in fact could be isomorphic to continuous flows.
Ser and Thr Residues Modulate the Conformation of Pro-Kinked Transmembrane ?-Helices
Deupi, Xavier; Olivella, Mireia; Govaerts, Cedric; Ballesteros, Juan Antonio; Campillo, Mercedes; Pardo, Leonardo
2004-01-01
Functionally required conformational plasticity of transmembrane proteins implies that specific structural motifs have been integrated in transmembrane helices. Surveying a database of transmembrane helices and the large family of G-protein coupled receptors we identified a series of overrepresented motifs associating Pro with either Ser or Thr. Thus, we have studied the conformation of Pro-kinked transmembrane helices containing Ser or Thr residues, in both g+ and g? rotamers, by molecular d...
Lierke, E. G.
2000-07-01
A 21 kHz standing-wave amplifier at the focus of a 36 cm diameter parabolic mirror (ka=70) is used for highly directive radiation of low frequency sine waves, voice signals and even music (of poor quality). The low frequency waves are amplitude-modulated onto the ultrasonic carrier wave and radiated into a solid angle of ±1° (-3 dB). Low frequency sound waves with frequencies between 50 Hz and 3 kHz are radiated over a distance of more than 20 m. The achievable audio sound pressure levels decrease with approximately 20 dB per distance doubling and reached about 30 dB at 20 m distance. The discussion of the measurements is based on Blackstock's weak shock theory [5] and on the nonsaturated radiation pressure at saturated sound pressure levels.
Hughes, D J; Heeley, E L
2014-01-01
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.
Swann, William C; Baumann, Esther; Giorgetta, Fabrizio R; Newbury, Nathan R
2011-11-21
Low phase-noise microwave generation has previously been demonstrated using self-referenced frequency combs to divide down a low noise optical reference. We demonstrate an approach based on a fs Er-fiber laser that avoids the complexity of self-referenced stabilization of the offset frequency. Instead, the repetition rate of the femtosecond Er-fiber laser is phase locked to two cavity-stabilized cw fiber lasers that span 3.74 THz by use of an intracavity electro-optic modulator with over 2 MHz feedback bandwidth. The fs fiber laser effectively divides the 3.74 THz difference signal to produce microwave signals at harmonics of the repetition rate. Through comparison of two identical dividers, we measure a residual phase noise on a 1.5 GHz carrier of -120 dBc/Hz at 1 Hz offset. PMID:22109466
Modulation of copper site properties by remote residues determines the stability of plastocyanins
Muñoz-López, F. J.; Frutos-Beltrán, Estrella; Díaz-Moreno, Sofía; Díaz-Moreno, Irene; Subías, G.; Rosa, Miguel A. de la; Díaz-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...
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
Syzygies Probing Scattering Amplitudes
Chen, Gang; Xie, Ruofei; Zhang, Hao; Zhou, Yehao
2015-01-01
We propose a new efficient algorithm to obtain the linearly independent basis of syzygies for an ideal, which are widely used in the current study of scattering amplitudes. This new algorithm, which can deal with more syzygies effectively owing to a new generation of syzygy in each step is given to verify the independence, is described in detail. We generalize this efficient algorithm to the module case, and partially guarantee the basis independence of the module. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the IBP relations of characteristic two-loop diagrams in the Yang-Mills theory.
International Nuclear Information System (INIS)
Solving a two-dimensional LTE (Local Thermodynamic Equilibrium) code, simulation of Ar-CO2 and Ar-N2 PMITP (Pulse Modulated Induction Thermal Plasma) has been carried out. The active plasma power, fundamental frequency and gas flow rate are 27 kW, 0.45 MHz and 100/102.5 slpm, respectively. It has been found that the injection of excess dissociative molecular gases, shrinks the plasma and slows down the plasma response at the instant of off-to-on-pulsing transition, which results mainly from the molecular dissociation and ionization. Plasma response has been found faster at higher SCL (Shimmer Current Level) for the same duty factor during the on pulsing transition, and hardly affected by SCL and molecular gas addition during off pulsing transition. Pressure does not appreciably affect the response of Ar-CO2 plasma, whereas response of Ar-N2 plasma becomes a bit faster at increased pressure. Part of the simulated results is compared with the corresponding experimental results. The agreement is found in some cases, and the remaining discrepancies between the results are critically evaluated with regard to various possible reasons
Neuropathic and inflammatory pain are modulated by tuberoinfundibular peptide of 39 residues.
Dimitrov, Eugene L; Kuo, Jonathan; Kohno, Kenji; Usdin, Ted B
2013-08-01
Nociceptive information is modulated by a large number of endogenous signaling agents that change over the course of recovery from injury. This plasticity makes understanding regulatory mechanisms involved in descending inhibition of pain scientifically and clinically important. Neurons that synthesize the neuropeptide TIP39 project to many areas that modulate nociceptive information. These areas are enriched in its receptor, the parathyroid hormone 2 receptor (PTH2R). We previously found that TIP39 affects several acute nociceptive responses, leading us to now investigate its potential role in chronic pain. Following nerve injury, both PTH2R and TIP39 knockout mice developed less tactile and thermal hypersensitivity than controls and returned to baseline sensory thresholds faster. Effects of hindpaw inflammatory injury were similarly decreased in knockout mice. Blockade of ?-2 adrenergic receptors increased the tactile and thermal sensitivity of apparently recovered knockout mice, returning it to levels of neuropathic controls. Mice with locus coeruleus (LC) area injection of lentivirus encoding a secreted PTH2R antagonist had a rapid, ?-2 reversible, apparent recovery from neuropathic injury similar to the knockout mice. Ablation of LC area glutamatergic neurons led to local PTH2R-ir loss, and barley lectin was transferred from local glutamatergic neurons to GABA interneurons that surround the LC. These results suggest that TIP39 signaling modulates sensory thresholds via effects on glutamatergic transmission to brainstem GABAergic interneurons that innervate noradrenergic neurons. TIP39's normal role may be to inhibit release of hypoalgesic amounts of norepinephrine during chronic pain. The neuropeptide may help maintain central sensitization, which could serve to enhance guarding behavior. PMID:23878240
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.
International Nuclear Information System (INIS)
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, Sds, the mean summit curvature, Ssc, the surface area ratio, Sdr, and the correlation length parameter, Scl37. 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, Sq, 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.
Javahiraly, Nicolas; Perrotton, Cédric; Chakari, Ayoub; Meyrueis, Patrick
2009-05-01
The reliable, accurate and low cost measurement of angular position is an important challenge for numerous industries such as aerospace or automotive industries. We propose a new optical fiber angular position sensor connected to an automotive power steering column. This sensor allows the measurement of the angular position of a car steering wheel over a large range (+/- 3 turns of wheel). The wheel rotation induces micro-bending in the transducer part of the optical fiber sensing system. This system operates as an amplitude modulation sensor based on mode coupling in the transducing fiber in the case when all the modes are equally excited. We study the sensor's response both theoretically and experimentally with a multimode step index optical fiber [Rf (fiber radius) = 300?m rc (core radius) = 50?m nc (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632, 8 nm at the ambient Temperature (20°C)]. This sensor has been tested between (-3x360) and (+3x360) degrees with 0,147 sensitivity. We show that the sensitivity can be controlled as a function of the sensor's length and the study of the sensor's output power as a function of the angular position has been achieved. We compare modeling and experimental validation and we conclude by a perspective of what could be soon an industrial sensor.
DEFF Research Database (Denmark)
Hancke, Kasper; Hancke, Torunn
2008-01-01
Short-term temperature effects on photosynthesis were investigated by measuring O2 production, PSII-fluorescence kinetics, and 14C-incorporation rates in monocultures of the marine phytoplankton species Prorocentrum minimum (Pavill.) J. Schiller (Dinophyceae), Prymnesium parvum f. patelliferum ( J. C. Green, D. J. Hibberd et Pienaar) A. Larsen (Coccolithophyceae), and Phaeodactylum tricornutum Bohlin (Bacillariophyceae), grown at 15 oC and 80 umol photons m-2 s-1. Photosynthesis versus irradiance curves were measured at seven temperatures (0oC to 30oC) by all three approaches. The maximum photosynthetic rate (PCmax) was strongly stimulated by temperature, reached an optimum for Pro. minimum only (20oC–25oC), and showed a similar relative temperature response for the three applied methods, with Q10 ranging from 1.7 to 3.5. The maximum light utilization coefficient (alfaC) was insensitive or decreased slightly with increasing temperature. Absolute rates of O2 production were calculated from pulse-amplitude-modulated (PAM) fluorometry measurements in combination with biooptical determination of absorbed quanta in PSII. The relationship between PAM-based O2 production and measured O2 production and 14C assimilation showed a species-specific correlation, with 1.2–3.3 times higher absolute values of PCmax and alfaC when calculated from PAM data for Pry. parvum and Ph. tricornutum but equivalent for Pro. minimum. The offset seemed to be temperature insensitive and could be explained by a lower quantum yield for O2 production than the theoretical maximum (due to Mehler-type reactions). Conclusively, the PAM technique can be used to study temperature responses of photosynthesis in microalgae when paying attention to the absorption properties in PSII.
Li, Heng-Yu; Perret-Aebi, Laure-Emmanuelle; Chapuis, Valentin; Ballif, Christophe; Luo, Yun
2015-01-01
A high-quality encapsulation process is crucial to ensuring the performance and long-term reliability of photovoltaic (PV) modules. In crystalline Si technology-based modules, poly (ethylene-co-vinyl acetate) (EVA) is the most widely used PV encapsulant. Its encapsulation process is usually performed in a flat-bed vacuum bag laminator. In certain types of laminators, cooling press can be applied to the module cooling process after the module encapsulation, leading to a much higher cooling rat...
Energy Technology Data Exchange (ETDEWEB)
Kubinyi, G.; Thuroczy, G.; Bakos, J.; Boeloeni, E.; Sinay, H.; Szabo, L.D. [National Frederic Joliot-Curie Research Inst. for Radiobiology and Radiohygiene, Budapest (Hungary)
1996-12-31
Investigations have been carried out concerning the effects of microwave (MW) exposure on the aminoacyl-transfer ribonucleic acid (tRNA) synthetase of the progeny of females that were exposed during their entire period of gestation (19 days). The changes caused by continuous-wave (CW) and amplitude-modulated (AM) MW radiation have been compared. CFLP mice were exposed to MW radiation for 100 min each day in an anechoic room. The MW frequency was 2.45 GHz, and the amplitude modulation had a 50 Hz rectangular waveform (on/off ratio, 50/50%). The average power density exposure was 3 mW/cm{sup 2}, and the whole body specific absorption rate (SAR) was 4.23 {+-} 0.63 W/kg. The weight and mortality of the progeny were followed until postnatal day 24. Aminoacyl-tRNA synthetase enzymes and tRNA from the brains and livers of the offspring (461 exposed, 487 control) were isolated. The aminoacyl-tRNA synthetase activities were determined. The postnatal increase of body weight and organ weight was not influenced by the prenatal MW radiation. The activity of enzyme isolated form the brain showed a significant decrease after CW MW exposure, but the changes were not significant after 50 Hz AM MW exposure. The activity of the enzyme isolated from liver increased under CW and 50 Hz modulated MW.
Korobov, A. I.; Izosimova, M. Yu.; Odina, N. I.
2015-05-01
Nonlinear scanning laser vibrometry is used for diagnostics of cylindrical resonators made of polycrystalline aluminum alloy with residual stresses and defects. The diagnostics is performed with flexural Lamb waves. The eigenmode frequency of such a resonator is found to depend on the amplitude of flexural Lamb waves excited in it (the fast dynamics effect), which points to the presence of a nonclassical nonlinear elasticity in the resonator material. Studying the nonlinear interactions between amplitude-modulated flexural Lamb waves in resonators allow the determination of the coordinates of defects and residual strains in them.
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.
DEFF Research Database (Denmark)
Assentoft, Mette; Larsen, Brian R
2014-01-01
Aquaporin 4 (AQP4) is the predominant water channel in the mammalian brain and is mainly expressed in the perivascular glial endfeet at the brain-blood interface. AQP4 serves as a water entry site during brain edema formation, and regulation of AQP4 may therefore be of therapeutic interest. Phosphorylation of aquaporins can regulate plasma membrane localization and, possibly, the unit water permeability via gating of the AQP channel itself. In vivo phosphorylation of six serine residues in the COOH terminus of AQP4 has been detected by mass spectrometry: Ser(276), Ser(285), Ser(315), Ser(316), Ser(321), and Ser(322). To address the role of these phosphorylation sites for AQP4 function, serine-to-alanine mutants were created to abolish the phosphorylation sites. All mutants were detected at the plasma membrane of transfected C6 cells, with the fraction of the total cellular AQP4 expressed at the plasma membrane of transfected C6 cells being similar between the wild-type (WT) and mutant forms of AQP4. Activation of protein kinases A, C, and G in primary astrocytic cultures did not affect the plasma membrane abundance of AQP4. The unit water permeability was determined for the mutant AQP4s upon heterologous expression in Xenopus laevis oocytes (along with serine-to-aspartate mutants of the same residues to mimic a phosphorylation). None of the mutant AQP4 constructs displayed alterations in the unit water permeability. Thus phosphorylation of six different serine residues in the COOH terminus of AQP4 appears not to be required for proper plasma membrane localization of AQP4 or to act as a molecular switch to gate the water channel.
DEFF Research Database (Denmark)
Assentoft, Mette; Larsen, Brian R
2014-01-01
Aquaporin 4 (AQP4) is the predominant water channel in the mammalian brain and is mainly expressed in the perivascular glial endfeet at the brain-blood interface. AQP4 serves as a water entry site during brain edema formation and regulation of AQP4 may therefore be of therapeutic interest. Phosphorylation of aquaporins can regulate plasma membrane localization and, possibly, the unit water permeability via gating of the AQP channel itself. In vivo phosphorylation of six serine residues in the C-terminus of AQP4 has been detected by mass spectrometry: Ser(276), Ser(285), Ser(315), Ser(316), Ser(321), and Ser(322). To address the role of these phosphorylation sites for AQP4 function, serine-to-alanine mutants were created to abolish the phosphorylation sites. All mutants were detected at the plasma membrane of transfected C6 cells, with the fraction of the total cellular AQP4 expressed at the plasma membrane of transfected C6 cells being similar between the WT and mutant forms of AQP4. Activation of protein kinases A, C and G in primary astrocytic cultures did not affect the plasma membrane abundance of AQP4. The unit water permeability was determined for the mutant AQP4s upon heterologous expression in Xenopus laevis oocytes (along with serine-to-aspartate mutants of the same residues to mimic a phosphorylation). None of the mutant AQP4 constructs displayed alterations in the unit water permeability. Thus, phosphorylation of six different serine residues in the C-terminus of AQP4 appears not to be required for proper plasma membrane localization of AQP4 or to act as a molecular switch to gate the water channel.
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
Salmon, Loïc; Giamba?u, George M; Nikolova, Evgenia N; Petzold, Katja; Bhattacharya, Akash; Case, David A; Al-Hashimi, Hashim M
2015-10-14
Approaches that combine experimental data and computational molecular dynamics (MD) to determine atomic resolution ensembles of biomolecules require the measurement of abundant experimental data. NMR residual dipolar couplings (RDCs) carry rich dynamics information, however, difficulties in modulating overall alignment of nucleic acids have limited the ability to fully extract this information. We present a strategy for modulating RNA alignment that is based on introducing variable dynamic kinks in terminal helices. With this strategy, we measured seven sets of RDCs in a cUUCGg apical loop and used this rich data set to test the accuracy of an 0.8 ?s MD simulation computed using the Amber ff10 force field as well as to determine an atomic resolution ensemble. The MD-generated ensemble quantitatively reproduces the measured RDCs, but selection of a sub-ensemble was required to satisfy the RDCs within error. The largest discrepancies between the RDC-selected and MD-generated ensembles are observed for the most flexible loop residues and backbone angles connecting the loop to the helix, with the RDC-selected ensemble resulting in more uniform dynamics. Comparison of the RDC-selected ensemble with NMR spin relaxation data suggests that the dynamics occurs on the ps-ns time scales as verified by measurements of R1? relaxation-dispersion data. The RDC-satisfying ensemble samples many conformations adopted by the hairpin in crystal structures indicating that intrinsic plasticity may play important roles in conformational adaptation. The approach presented here can be applied to test nucleic acid force fields and to characterize dynamics in diverse RNA motifs at atomic resolution. PMID:26306428
Amplitude-mode dynamics of polariton condensates
EASTHAM, PAUL
2011-01-01
We study the stability of collective amplitude excitations in nonequilibrium polariton condensates. These excitations correspond to renormalized upper polaritons and to the collective amplitude modes of atomic gases and superconductors. They would be present following a quantum quench or could be created directly by resonant excitation. We show that uniform amplitude excitations are unstable to the production of excitations at finite wave vectors, leading to the formation of density-modulated...
Detecting Pesticide Residue by Using Modulating Temperature Over a Single SnO2-Based Gas Sensor
Directory of Open Access Journals (Sweden)
Zengliang Yu
2003-09-01
Full Text Available A new rapid detecting method (called dynamic measurements was reported to detect and distinguish the presence of two pesticide gases in the ambient atmosphere. The method employed only a single SnO2-based gas sensor in a rectangular temperature mode to perform the qualitative analysis of a binary gas mixture (acephate and trichlorphon in air. Polar plots was used for quantitative analysis which the feature extraction was performed by FFT. Experimental results showed that high selectivity of the sensor achieved in the range of 250~3000C and modulating frequency 20mHz, one can easily observe the qualitative difference among the response to pure acephate and trichlorphon gases of the same concentration and to the mixture, and the concentration of pesticide gases can be obtained based on the changes of polar plots.
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...
Scattering Amplitudes in Gauge Theories
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...
International Nuclear Information System (INIS)
Purpose: To estimate the dosimetric impact of residual setup errors on parotid sparing in head-and-neck (H and N) intensity-modulated treatments and to evaluate the effect of employing an PRV (planning organ-at-risk volume) margin for the parotid gland. Patients and methods: Ten patients treated for H and N cancer were considered. A nine-beam intensity-modulated radiotherapy (IMRT) was planned for each patient. A second optimization was performed prescribing dose constraint to the PRV of the parotid gland. Systematic setup errors of 2 mm, 3 mm, and 5 mm were simulated. The dose-volume histograms of the shifted and reference plans were compared with regard to mean parotid gland dose (MPD), normal-tissue complication probability (NTCP), and coverage of the clinical target volume (V95% and equivalent uniform dose [EUD]); the sensitivity of parotid sparing on setup error was evaluated with a probability-based approach. Results: MPD increased by 3.4%/mm and 3.0%/mm for displacements in the craniocaudal and lateral direction and by 0.7%/mm for displacements in the anterior-posterior direction. The probability to irradiate the parotid with a mean dose > 30 Gy was > 50%, for setup errors in cranial and lateral direction and 95% and EUD variations < 1% and < 1 Gy). Conclusion: The parotid gland is more sensitive to craniocaudal and lateral displacements. A setup error of 2 mm guarantees an MPD ? 30 Gy in most cases, without adding a PRV margin. If greater displacements are expected/accepted, an adequate PRV margin could be used to meet the clinical parotid gland constraint of 30 Gy, without affecting target volume coverage. (orig.)
Modulation masking produced by complex-tone modulators
DEFF Research Database (Denmark)
Ewert, Stephan; Verhey, J.L.; Dau, Torsten
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 i...
Residual deposits (residual soil)
International Nuclear Information System (INIS)
Residual soil deposits is accumulation of new formate ore minerals on the earth surface, arise as a result of chemical decomposition of rocks. As is well known, at the hyper genes zone under the influence of different factors (water, carbonic acid, organic acids, oxygen, microorganism activity) passes chemical weathering of rocks. Residual soil deposits forming depends from complex of geologic and climatic factors and also from composition and physical and chemical properties of initial rocks
Scattering Amplitudes via Algebraic Geometry Methods
DEFF Research Database (Denmark)
SØgaard, Mads
2015-01-01
This thesis describes recent progress in the understanding of the mathematical structure of scattering amplitudes in quantum field theory. The primary purpose is to develop an enhanced analytic framework for computing multiloop scattering amplitudes in generic gauge theories including QCD without Feynman diagrams. The study of multiloop scattering amplitudes is crucial for the new era of precision phenomenology at the Large Hadron Collider (LHC) at CERN. Loop-level scattering amplitudes can be reduced to a basis of linearly independent integrals whose coefficients are extracted from generalized unitarity cuts. We take advantage of principles from algebraic geometry in order to extend the notion of maximal cuts to a large class of two- and three-loop integrals. This allows us to derive unique and surprisingly compact formulae for the coefficients of the basis integrals. Our results are expressed in terms of certain linear combinations of multivariate residues and elliptic integrals computed from products of tree-level amplitudes. Several explicit examples are provided
Energy Technology Data Exchange (ETDEWEB)
Delana, Anna; Menegotti, Loris; Valentini, Aldo [Dept. of Medical Physics, S. Chiara Hospital, APSS Trento (Italy); Bolner, Andrea; Tomio, Luigi; Vanoni, Valentina [Div. of Radiation Oncology, S. Chiara Hospital, APSS Trento (Italy); Lohr, Frank [Dept. of Radiation Oncology, Univ. Medical Center Mannheim, Univ. of Heidelberg, Mannheim (Germany)
2009-07-15
Purpose: To estimate the dosimetric impact of residual setup errors on parotid sparing in head-and-neck (H and N) intensity-modulated treatments and to evaluate the effect of employing an PRV (planning organ-at-risk volume) margin for the parotid gland. Patients and methods: Ten patients treated for H and N cancer were considered. A nine-beam intensity-modulated radiotherapy (IMRT) was planned for each patient. A second optimization was performed prescribing dose constraint to the PRV of the parotid gland. Systematic setup errors of 2 mm, 3 mm, and 5 mm were simulated. The dose-volume histograms of the shifted and reference plans were compared with regard to mean parotid gland dose (MPD), normal-tissue complication probability (NTCP), and coverage of the clinical target volume (V{sub 95%} and equivalent uniform dose [EUD]); the sensitivity of parotid sparing on setup error was evaluated with a probability-based approach. Results: MPD increased by 3.4%/mm and 3.0%/mm for displacements in the craniocaudal and lateral direction and by 0.7%/mm for displacements in the anterior-posterior direction. The probability to irradiate the parotid with a mean dose > 30 Gy was > 50%, for setup errors in cranial and lateral direction and < 10% in the anterior-posterior direction. The addition of a PRV margin improved parotid sparing, with a relative reduction in NTCP of 14%. The PRV margin compensates for setup errors of 3 mm and 5 mm (MPD {<=} 30 Gy in 87% and 60% of cases), without affecting clinical target volume coverage (V{sub 95%} and EUD variations < 1% and < 1 Gy). Conclusion: The parotid gland is more sensitive to craniocaudal and lateral displacements. A setup error of 2 mm guarantees an MPD {<=} 30 Gy in most cases, without adding a PRV margin. If greater displacements are expected/accepted, an adequate PRV margin could be used to meet the clinical parotid gland constraint of 30 Gy, without affecting target volume coverage. (orig.)
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 applications)
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.
Directory of Open Access Journals (Sweden)
O. Uchino
2012-07-01
Full Text Available Simultaneous measurements of the partial column-averaged dry air mixing ratio of CO2 (q and target range were demonstrated using airborne amplitude-modulated 1.57 ?m differential laser absorption spectrometry (LAS. The LAS system is useful for discriminating between ground and cloud return signals and has a demonstrated ability to suppress the impact of integrated aerosol signals on differential absorption optical depth (?? measurements. A high correlation coefficient (R of 0.99 between ?? observed by LAS and ?? calculated from in-situ measurements of CO2 was obtained. The averaged difference in q obtained from LAS (qLAS and validation data (qval was within 1.5 ppm for all spiral measurements. A significant profile was observed for both qLAS and qval, in which lower altitude CO2 decreases compared to higher altitude CO2 attributed to the photosynthesis over grassland in the summer. In the case of an urban area where CO2 and aerosol are highly distributed in the lower atmosphere in the winter, the difference of qLAS to qval is ?1.5 ppm, and evaluated qLAS is in agreement with qval within the measurement precision of 2.4 ppm (1?.
Construction of diffractive amplitudes
International Nuclear Information System (INIS)
Starting from a simple parametrization of production amplitudes an explicit construction of the diffractive elastic amplitude through multiparticle unitarity is given. It is shown that the phase cancellation effect is essential in order to obtain an elastic amplitude which displays a diffractive peak in qualitative agreement with the data
High-frequency accelerating field amplitude programmer for electron synchrotron
International Nuclear Information System (INIS)
A system for forming the amplitude modulation of the high-frequency accelerating voltage of an electronic synchrotron based on information about the guiding magnetic field of the synchrotron is described. The circuit permits regulating the scale factors of the hf voltage modulation independently of one another which makes it possible to modulate the hf voltage amplitude over a wide range. The system employs analog functional units which enable automatic formation of the required modulation law when the accelerator is tuned from one energy to another. The modulation law is set with a relative accuracy of plus or minus 1%
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)
Amplitude mediated chimera states
Sethia, Gautam C; Sen, Abhijit; Johnston, George L.
2013-01-01
We investigate the possibility of obtaining chimera state solutions of the non-local 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 non-stationary two cluster chimera states), that display intermittent emergence and decay of amplitude dips in their phase incoherent regions. The exis...
Periods and Feynman amplitudes
Brown, Francis
2016-01-01
Feynman amplitudes in perturbation theory form the basis for most predictions in particle collider experiments. The mathematical quantities which occur as amplitudes include values of the Riemann zeta function and relate to fundamental objects in number theory and algebraic geometry. This talk reviews some of the recent developments in this field, and explains how new ideas from algebraic geometry have led to much progress in our understanding of amplitudes. In particular, the idea that certain transcendental numbers, such as $\\pi$, can be viewed as a representation of a group, provides a powerful framework to study amplitudes which reveals many hidden structures.
Penkett, CJ; Dobson, CM; Smith, LJ; Bright, JR; Pickford, AR; Campbell, ID; Potts, JR
2000-01-01
Many pathogenic Gram-positive bacteria express cell surface proteins that bind to components of the extracellular matrix. This paper describes studies of the interaction between ligand binding repeats (D3 and D1-D4) of a fibronectin-binding protein from Staphylococcus aureus with a module pair ((4)F1(5)F1) from the N-terminal region of fibronectin. When D3 was added to isotope-labeled (4)F1(5)F1, (1)H, (15)N, and (13)C NMR chemical shift changes indicate that binding is primarily via residues...
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.
On the parametrization of the ? residue function
International Nuclear Information System (INIS)
The complex residues at the ?(1236) and ?(1950) poles in the relevant partial-wave amplitudes provide information on the behaviour of the ? Regge residue function in the resonance region u>0. Attempts to incorporate this information in parametrizations of the residue by functions that are real on the real u-axis result in residues which have unsatisfactory behaviour in the region u2. The choice of complex functions for the trajectory and residue removes this undesirable feature and provides a better representation of the residue in the resonance region, suggesting that complex parametrizations would be better suited to Regge analyses of near-backward scattering. (Auth.)
Writing CFT correlation functions as AdS scattering amplitudes
Penedones, Joao
2011-03-01
We explore the Mellin representation of conformal correlation functions recently proposed by Mack. Examples in the AdS/CFT context reinforce the analogy between Mellin amplitudes and scattering amplitudes. We conjecture a simple formula relating the bulk scattering amplitudes to the asymptotic behavior of Mellin amplitudes and show that previous results on the flat space limit of AdS follow from our new formula. We find that the Mellin amplitudes are particularly useful in the case of conformal gauge theories in the planar limit. In this case, the four point Mellin amplitudes are meromorphic functions whose poles and their residues are entirely determined by two and three point functions of single-trace operators. This makes the Mellin amplitudes the ideal objects to attempt the conformal bootstrap program in higher dimensions.
Writing CFT correlation functions as AdS scattering amplitudes
Penedones, Joao
2010-01-01
We explore the Mellin representation of conformal correlation functions recently proposed by Mack. Examples in the AdS/CFT context reinforce the analogy between Mellin amplitudes and scattering amplitudes. We conjecture a simple formula relating the bulk scattering amplitudes to the asymptotic behavior of Mellin amplitudes and show that previous results on the flat space limit of AdS follow from our new formula. We find that the Mellin amplitudes are particularly useful in the case of conformal gauge theories in the planar limit. In this case, the four point Mellin amplitudes are meromorphic functions whose poles and their residues are entirely determined by two and three point functions of single-trace operators. This makes the Mellin amplitudes the ideal objects to attempt the conformal bootstrap program in higher dimensions.
Fatigue Reliability under Multiple-Amplitude Loads
DEFF Research Database (Denmark)
Talreja, R.
1979-01-01
A method to determine the fatigue of structures subjected to multiple-amplitude loads is presented. Unlike the more common cumulative damage methods, which are usually based on fatigue life data, the proposed method is based on tensile strength data. Assuming the Weibull distribution for the initial tensile strength and the fatigue life, the probability distributions for the residual tensile strength in both the crack initiation and the crack propagation stages of fatigue are determined. The met...
Open bosonic string amplitudes
International Nuclear Information System (INIS)
The theory of the partially U(1) compactified scalar massless field on the domain on the compact Riemann surface with Nambu-Goto action is defined. The partition function is determined completely by a choice of the finite-dimensional approximations. The correlation functions are the correctly defined objects of the theory. The averages of the correlation function asymptotic values provide the amplitudes. The Nielsen's conjecture for the scattering amplitudes is correctly proved. 8 refs
Cattani, Eduardo; Dickenstein, Alicia; Sturmfels, Bernd
2000-01-01
A binomial residue is a rational function defined by a hypergeometric integral whose kernel is singular along binomial divisors. Binomial residues provide an integral representation for rational solutions of A-hypergeometric systems of Lawrence type. The space of binomial residues of a given degree, modulo those which are polynomial in some variable, has dimension equal to the Euler characteristic of the matroid associated with A.
Poretti, Ennio; Rainer, Monica; Weiss, Werner W.; Bognar, Zsofia; Moya, Andy; Niemczura, Ewa; Suarez, Juan Carlos; Auvergne, Michel; Annie BAGLIN; 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 b...
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
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)
Hodges, Andrew
2015-08-01
A brief review is given of why twistor geometry has taken a central place in the theory of scattering amplitudes for fundamental particles. The emphasis is on the twistor diagram formalism as originally proposed by Penrose, the development of which has now led to the definition by Arkani-Hamed et al. of the 'amplituhedron'. PMID:26124244
Large amplitude gravitational waves
Ali, G.; Hunter, J. K.
1998-01-01
We derive an asymptotic solution of the Einstein field equations which describes the propagation of a thin, large amplitude gravitational wave into a curved space-time. The resulting equations have the same form as the colliding plane wave equations without one of the usual constraint equations.
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 stimulus-locked P3b. This mixing effect is disproportionately larger in older adults who also prepare more for and respond more cautiously on these "mixed" repeat trials (Karayanidis et al., 2011). In this paper, we analyze stimulus-locked and response-locked P3 and lateralized readiness potentials to identify whether residual switch and mixing cost arise from the need to control interference at the level of stimulus processing or response processing. Residual mixing cost was associated with control of stimulus-level interference, whereas residual switch cost was also associated with a delay in response selection. In older adults, the disproportionate increase in mixing cost was associated with greater interference at the level of decision-response mapping and response programming for repeat trials in mixed-task blocks. These findings suggest that older adults strategically recruit greater proactive and reactive control to overcome increased susceptibility to post-stimulus interference. This interpretation is consistent with recruitment of compensatory strategies to compensate for reduced repetition benefit rather than an overall decline on cognitive flexibility. PMID:24817859
Lam, C S
2015-01-01
The Cachazo-He-Yuan (CHY) formula for on-shell scattering amplitudes are extended off-shell. The off-shell amplitudes are M\\"obius invariant, and have the same momentum poles as the on-shell amplitudes. The same technique is also used to obtain off-shell massive scalar and vector boson amplitudes.
International Nuclear Information System (INIS)
Residual stresses are stresses which exist in a material without the influence of external powers and moments. They come into existence when the volume of a material constantly changes its form as a consequence of mechanical, thermal, and/or chemical processes and is hindered by neighbouring volumes. Bodies with residual stress are in mechanical balance. These residual stresses can be manifested by means of all mechanical interventions disturbing this balance. Acoustical, optical, radiological, and magnetical methods involving material changes caused by residual stress can also serve for determining residual stress. Residual stresses have an ambivalent character. In technical practice, they are feared and liked at the same time. They cause trouble because they can be the cause for unexpected behaviour of construction elements. They are feared since they can cause failure, in the worst case with catastrophical consequences. They are appreciated, on the other hand, because, in many cases, they can contribute to improvements of the material behaviour under certain circumstances. But they are especially liked for their giving convenient and (this is most important) mostly uncontrollable explanations. For only in very few cases we have enough knowledge and possibilities for the objective evaluation of residual stresses. (orig.)
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 ...
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)
Quantitative Seismic Amplitude Analysis:
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...
Connection between the period and the amplitude of the Blazhko effect
Directory of Open Access Journals (Sweden)
Benk? József M.
2015-01-01
Full Text Available We found a possible relationship between the modulation period and the amplitude of the Blazhko RR Lyrae stars: long modulation period generally implies high modulation amplitude while the short modulation period results in small amplitude. Although this effect is much more a tendency than a strict rule, it can be detected easily in the space-born time series data produced by Kepler and CoRoT. Good quality ground-based data show this relation, too. This phenomenon could give us constraints for the physics of the Blazhko effect.
International Nuclear Information System (INIS)
Patients with locally advanced head and neck cancer (LAHNC) undergo life-changing treatments that can seriously affect quality of life (QoL). This prospective study examined the key QoL domains during the first year after intensity-modulated radiotherapy (IMRT) and identified predictors of these changes in order to improve patient outcomes. A consecutive series of patients with LAHNC completed the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core module (QLQ-C30) and the HNC-specific QLQ-HN35 before (t0) and at the end (t1) of definitive or adjuvant IMRT, then at 6-8 weeks (t2), 6 months (t3), and 1 year (t4) after IMRT. Patients (n = 111) completing questionnaires at all five time points were included (baseline response rate: 99 %; dropout rate between t0 and t4: 5 %). QoL deteriorated in all domains during IMRT and improved slowly during the first year thereafter. Many domains recovered to baseline values after 1 year but problems with smelling and tasting, dry mouth, and sticky saliva remained issues at this time. Increases in problems with sticky saliva were greater after 1 year in patients with definitive versus adjuvant IMRT (F = 3.5, P = 0.05). QoL in patients with LAHNC receiving IMRT takes approximately 1 year to return to baseline; some domains remain compromised after 1 year. Although IMRT aims to maintain function and QoL, patients experience long-term dry mouth and sticky saliva, particularly following definitive IMRT. Patients should be counseled at the start of therapy to reduce disappointment with the pace of recovery. (orig.)
Direct modulation of 56 Gbps duobinary-4-PAM
DEFF Research Database (Denmark)
Suhr, Lau Frejstrup; Vegas Olmos, Juan José
2015-01-01
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.
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.
International Nuclear Information System (INIS)
It is normal in high energy physics to measure the time of flight of a particle in order to determine its mass. This can be done by the method which consists in transforming the time measurement into an analysis of amplitude, which is easier; a time-amplitude converter has therefore been built for this purpose. The apparatus here described uses a double grid control tube 6 BN 6 whose resolution time, as measured with a pulse generator, is 5 x 10-11 s. The analysis of the response of a particle counter, made up of a scintillator and a photomultiplier, indicates that a time of resolution of 5 x 10-10 s. can be obtained. A time of this order of magnitude is obtained experimentally with the converter. This converter has been used in the study of the time of flight of particles in a secondary beam of the accelerator Saturne. It has thus been possible to measure the energy spectrum of ?-mesons, of protons, and of deutons emitted from a polyethylene target bombarded by 1,4 and 2 GeV protons. (author)
Computational Prediction of Hot Spot Residues
Morrow, John Kenneth; Zhang, Shuxing
2012-01-01
Most biological processes involve multiple proteins interacting with each other. It has been recently discovered that certain residues in these protein-protein interactions, which are called hot spots, contribute more significantly to binding affinity than others. Hot spot residues have unique and diverse energetic properties that make them challenging yet important targets in the modulation of protein-protein complexes. Design of therapeutic agents that interact with hot spot residues has pr...
Generator of stable amplitude spectroscopy pulses
International Nuclear Information System (INIS)
A generator aimed at energy spectrum calibration and testing of electronics is described. The device is performed as a CAMAC 2M module and consists of a current pulses generator and charge sensitive amplifier. Both the self-oscillation regime and primary launched regime are possible. The output frequency can vary from 20 to 200 Hz. The maximal amplitude of single pulse is 5 V for a high-resistance load and 2.5 V for 50 ?. A stable amplitude of spectroscopic pulses (0.01%/oC) is insured. It is possible to use the device as a generator of double pulses, delay can vary from 80 ns to 100 ?s between pulses in the pair in this case. (author)
Energy Technology Data Exchange (ETDEWEB)
Tribius, Silke; Raguse, Marieclaire; Voigt, Christian; Petersen, Cordula; Kruell, Andreas [University Medical Center Hamburg-Eppendorf, Department of Radiation Oncology, Hamburg (Germany); Muenscher, Adrian [University Medical Center Hamburg-Eppendorf, Department of Otorhinolaryngology and Head and Neck Surgery, Hamburg (Germany); Groebe, Alexander [University Medical Center Hamburg-Eppendorf, Department of Maxillofacial Surgery, Hamburg (Germany); Bergelt, Corinna [University Medical Center Hamburg-Eppendorf, Department of Medical Psychology, Hamburg (Germany); Singer, Susanne [University Medical Center Mainz, Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), Mainz (Germany)
2015-03-08
Patients with locally advanced head and neck cancer (LAHNC) undergo life-changing treatments that can seriously affect quality of life (QoL). This prospective study examined the key QoL domains during the first year after intensity-modulated radiotherapy (IMRT) and identified predictors of these changes in order to improve patient outcomes. A consecutive series of patients with LAHNC completed the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core module (QLQ-C30) and the HNC-specific QLQ-HN35 before (t0) and at the end (t1) of definitive or adjuvant IMRT, then at 6-8 weeks (t2), 6 months (t3), and 1 year (t4) after IMRT. Patients (n = 111) completing questionnaires at all five time points were included (baseline response rate: 99 %; dropout rate between t0 and t4: 5 %). QoL deteriorated in all domains during IMRT and improved slowly during the first year thereafter. Many domains recovered to baseline values after 1 year but problems with smelling and tasting, dry mouth, and sticky saliva remained issues at this time. Increases in problems with sticky saliva were greater after 1 year in patients with definitive versus adjuvant IMRT (F = 3.5, P = 0.05). QoL in patients with LAHNC receiving IMRT takes approximately 1 year to return to baseline; some domains remain compromised after 1 year. Although IMRT aims to maintain function and QoL, patients experience long-term dry mouth and sticky saliva, particularly following definitive IMRT. Patients should be counseled at the start of therapy to reduce disappointment with the pace of recovery. (orig.) [German] Die Therapie von Patienten mit lokal fortgeschrittenen Kopf-Hals-Tumoren (LFKHT) geht mit einschneidenden Veraenderungen einher und beeinflusst die Lebensqualitaet (LQ) erheblich. Diese prospektive Studie untersucht die LQ waehrend des ersten Jahres nach intensitaetsmodulierter Strahlentherapie (IMRT) und hat Praediktoren dieser Veraenderungen herausgearbeitet, um Therapieergebnisse verbessern zu koennen. Patienten mit LFKHT fuellten Lebensqualitaetsfrageboegen der European Organisation for Research and Treatment of Cancer (EORTC) aus; Hauptfragebogen (QLQ-C30) und Kopf-Hals-Tumor-Fragebogen (QLQ-HN35) jeweils vor definitiver oder adjuvanter IMRT (t0), am Ende der IMRT (t1), nach weiteren 6-8 Wochen (t2), 6 Monaten (t3) und nach 1 Jahr (t4). Insgesamt haben 111 Patienten zu allen fuenf Zeitpunkten die Frageboegen ausgefuellt und wurden in die Studie eingeschlossen (Responserate t0: 99%; Ausfallrate t0-t4: 5 %). Waehrend der IMRT verschlechterten sich alle Domaenen der LQ und besserten sich langsam ueber das erste Folgejahr. Viele Lebensqualitaetswerte kehrten zum Ausgangsniveau zurueck, waehrend Probleme mit Riechen und Schmecken, trockener Mund und klebriger Speichel problematisch blieben. Probleme mit klebrigem Speichel wurden von Patienten nach definitiver IMRT haeufiger berichtet als von Patienten nach adjuvanter Therapie (F = 3,5; P = 0,05). Nach einer IMRT dauert es bei Patienten mit Kopf-Hals-Tumoren bis zu 1 Jahr bis die LQ wieder ihr Ausgangsniveau erreicht; einige Domaenen bleiben auch noch nach 1 Jahr darunter. Obwohl es Ziel der IMRT ist, Funktion und LQ zu erhalten, bleiben trockener Mund und klebriger Speichel teilweise als Langzeiteffekte bestehen, insbesondere bei Patienten nach primaerer IMRT. Patienten sollten diesbezueglich vor Beginn der Therapie aufgeklaert werden, um ihnen Unzufriedenheit mit der Geschwindigkeit der Rekonvaleszenz zu ersparen. (orig.)
Fringe free holographic measurements of large amplitude vibrations
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.
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.
Reeves, Philip T
2010-01-01
The use of veterinary drugs in animal production is necessary for the prevention and treatment of disease; however, such use may result in residues. Regulatory authorities administer legislative frameworks which ensure that foods derived from animals treated with approved veterinary drugs are safe for human consumption. A human food safety evaluation is conducted as follows: it estimates the risk to human health and safety--based on scientific assessment of the available information and data--formulates measures for controlling the risks identified, and communicates the findings and implications of the risk assessment to interested parties. Foods derived from animals are monitored for the presence of drug residues. The reported incidence of illegal residues from these programmes is very low. These findings reassure the public that veterinary drugs are effectively regulated and that food obtained from treated animals does not contain residues that might constitute a health hazard to consumers. Non-regulatory organizations, including the veterinary pharmaceutical industry, producer organisations, veterinarians and food processors, all contribute to a safe food supply. The food safety risk analysis framework is continually refined to ensure that the health of all consumers is protected. PMID:20204591
Multidimensional signal modulation and/or demodulation for data communications
Smith, Stephen F. (London, TN); Dress, William B. (Camas, WA)
2008-03-04
Systems and methods are described for multidimensional signal modulation and/or demodulation for data communications. A method includes modulating a carrier signal in a first domain selected from the group consisting of phase, frequency, amplitude, polarization and spread; modulating the carrier signal in a second domain selected from the group consisting of phase, frequency, amplitude, polarization and spread; and modulating the carrier signal in a third domain selected from the group consisting of phase, frequency, amplitude, polarization and spread.
Full one-loop amplitudes from tree amplitudes
International Nuclear Information System (INIS)
We establish an efficient polynomial-complexity algorithm for one-loop calculations, based on generalized D-dimensional unitarity. It allows automated computations of both cut-constructible and rational parts of one-loop scattering amplitudes from on-shell tree amplitudes. We illustrate the method by (re)-computing all four-, five- and six-gluon scattering amplitudes in QCD at one-loop
International Nuclear Information System (INIS)
This paper discusses when and how the Verlinde dimensions of a rational conformal field theory can be expressed as correlation functions in a topical LG theory. It is seen that a necessary condition is that the RCFT fusion rules must exhibit an extra symmetry. The authors consider two particular perturbations of the Grassmannian superpotentials. The topological LG residues in one perturbation, introduced by Gepner, are shown to be a twisted version of the SU(N)k Verlinde dimensions. The residues in the other perturbations are the twisted Verlinde dimensions of another RCFT; these topological LG correlation functions are conjectured to be the correlation functions of the corresponding Grassmannian topological sigma model with a coupling in the action to instanton number
Intriligator, Kenneth
1991-01-01
We discuss when and how the Verlinde dimensions of a rational conformal field theory can be expressed as correlation functions in a topological LG theory. It is seen that a necessary condition is that the RCFT fusion rules must exhibit an extra symmetry. We consider two particular perturbations of the Grassmannian superpotentials. The topological LG residues in one perturbation, introduced by Gepner, are shown to be a twisted version of the $SU(N)_k$ Verlinde dimensions. The...
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)
Chen, Hao; Ding, Jianping; Li, Guoqiang
2015-01-01
We present an approach that enables complete control over the amplitude, phase and arbitrary polarization state on the Poincar\\'e sphere of an optical beam in a 4-f system with a spatial light modulator (SLM). The beams can be constructed from a coaxial superposition of x- and y-linearly polarized light, each carrying structured amplitude profile and phase distributions by using an amplitude-modulated mask imposed on the SLM. The amplitude, phase and polarization distribution of vector beams with four free parameters can be tailored independently and simultaneously by the SLM.
Simultaneous tailoring of complete polarization, amplitude and phase of vector beams
Yu, Zhongliang; Chen, Hao; Chen, Zhaozhong; Hao, Jingjing; Ding, Jianping
2015-06-01
We propose and experimentally demonstrate the complete and simultaneous modulation of the amplitude, phase and arbitrary state of polarization spanning the entire surface of the Poincaré sphere. By using a single spatial light modulator (SLM), we can create vector beams from a coaxial superposition of x- and y-linearly polarized light, each carrying the structured amplitude profile and phase distribution, which result from a two-dimensional holographic grating pattern that is imposed on the SLM. By manipulating four free modulation parameters imbedded in the SLM grating we can realize the independent and simultaneous tailoring of the amplitude, phase and polarization distribution of vector beams.
Hidden Beauty in Multiloop Amplitudes
Cachazo, Freddy; Spradlin, Marcus; Volovich, Anastasia
2006-01-01
Planar L-loop maximally helicity violating amplitudes in N = 4 supersymmetric Yang-Mills theory are believed to possess the remarkable property of satisfying iteration relations in L. We propose a simple new method for studying the iteration relations for four-particle amplitudes which involves the use of certain linear differential operators and eliminates the need to fully evaluate any loop integrals. We carry out this procedure in explicit detail for the two-loop amplitud...
Higher-order amplitude squeezing
Shchukin, E.; Vogel, W.
2006-04-01
A brief review of nonclassicality conditions in terms of moments of the creation and annihilation operators is given. By introducing k-th power amplitude squeezing, the notions of ordinary quadrature squeezing and amplitude-squared squeezing are generalized. Minimum uncertainty states are considered as a special class of k-th power amplitude squeezed states. These states can be characterized by a special, rather simple nonclassicality condition.
Higher-order amplitude squeezing
International Nuclear Information System (INIS)
A brief review of nonclassicality conditions in terms of moments of the creation and annihilation operators is given. By introducing k-th power amplitude squeezing, the notions of ordinary quadrature squeezing and amplitude-squared squeezing are generalized. Minimum uncertainty states are considered as a special class of k-th power amplitude squeezed states. These states can be characterized by a special, rather simple nonclassicality condition
Cross-Channel Amplitude Sweeps Are Crucial to Speech Intelligibility
Prendergast, Garreth; Green, Gary G. R.
2012-01-01
Classical views of speech perception argue that the static and dynamic characteristics of spectral energy peaks (formants) are the acoustic features that underpin phoneme recognition. Here we use representations where the amplitude modulations of sub-band filtered speech are described, precisely, in terms of co-sinusoidal pulses. These pulses are…
Finite amplitude waves on barotropic shear layers and jets
Meacham, S. P.; Flierl, G. R.
We give a detailed derivation of the amplitude equations governing weak, slowly modulated, varicose wavetrains on a barotropic, triangular jet on a -plane. As one might expect, at wavenumbers that are neutral by linear theory, well-behaved wavetrain solutions can be found. Such solutions are not unique. The properties of the wavetrain (in particular, the form of the nonlinear coefficient in the amplitude equation) depend upon assumptions that one makes about the structure of the wave field in the region far from the jet. Such assumptions turn out to be equivalent to assumptions made about the initial conditions of the problem. This link is established by a wave packet analysis that retains separate, nondimensional parameters for the amplitude of the wavetrain and the length scale of the modulation envelope. We briefly state similar results for sinuous waves on a triangular jet and for waves on a shear layer composed of a strip of uniform potential vorticity.
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 benefit most from IMRT. Our early clinical experience of HT-based IMRT for brain tumors has been encouraging.
Small-amplitude defocusing nematicons
Horikis, Theodoros P.
2015-01-01
Using a perturbation theory based on multiple scales analysis we obtain small amplitude nematicon structures in the defocusing (normal dispersion) regime. The nonlocal equations that describe light propagation through a liquid crystal are reduced to a Korteweg–de Vries (KdV) equation. As such, it is found that under certain conditions there exist dark and anti-dark (small amplitude) nematicons; the criterion is the sign of a constant quantity that relates to the physical parameters of the system. The amplitudes, velocities and phases of these pulses are obtained in closed form and are closely related to the soliton solution of the related KdV equation.
Mapping Pn amplitude spreading and attenuation in Asia
Energy Technology Data Exchange (ETDEWEB)
Yang, Xiaoning [Los Alamos National Laboratory; Phillips, William S [Los Alamos National Laboratory; Stead, Richard J [Los Alamos National Laboratory
2010-12-06
Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.
Positive Amplitudes In The Amplituhedron
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...
Small amplitude quasibreathers and oscillons
International Nuclear Information System (INIS)
Quasibreathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in [Phys. Rev. D 74, 124003 (2006)]. QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in D spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, Dcrit=4, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.
Amplitude-mediated chimera 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.
Model selection for amplitude analysis
Guegan, B.; Hardin, J.; Stevens, J.; Williams, M.
2015-09-01
Model complexity in amplitude analyses is often a priori under-constrained since the underlying theory permits a large number of possible amplitudes to contribute to most physical processes. The use of an overly complex model results in reduced predictive power and worse resolution on unknown parameters of interest. Therefore, it is common to reduce the complexity by removing from consideration some subset of the allowed amplitudes. This paper studies a method for limiting model complexity from the data sample itself through regularization during regression in the context of a multivariate (Dalitz-plot) analysis. The regularization technique applied greatly improves the performance. An outline of how to obtain the significance of a resonance in a multivariate amplitude analysis is also provided.
Model selection for amplitude analysis
Guegan, Baptiste; Stevens, Justin; Williams, Mike
2015-01-01
Model complexity in amplitude analyses is often a priori under-constrained since the underlying theory permits a large number of amplitudes to contribute to most physical processes. The use of an overly complex model results in reduced predictive power and worse resolution on unknown parameters of interest. Therefore, it is common to reduce the complexity by removing from consideration some subset of the allowed amplitudes. This paper studies a data-driven method for limiting model complexity through regularization during regression in the context of a multivariate (Dalitz-plot) analysis. The regularization technique applied greatly improves the performance. A method is also proposed for obtaining the significance of a resonance in a multivariate amplitude analysis.
Scattering amplitudes in gauge theories
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 ...
Directory of Open Access Journals (Sweden)
FriniKarayanidis
2014-04-01
Full Text Available 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 P3b. This mixing effect is disproportionately larger in older adults who also prepare more for and respond more cautiously on these ‘mixed’ repeat trials (Karayanidis et al., 2011. In this study, we examine stimulus-locked and response-locked P3 and lateralized readiness potentials to identify whether residual switch and mixing cost arise from the need to control interference at the level of stimulus processing or response processing. Residual mixing cost was associated with control of stimulus-level interference, whereas residual switch cost was also associated with a delay in response selection. In older adults, the disproportionate increase in mixing cost was associated with greater interference at the level of decision-response mapping and response programming for repeat trials in mixed-task blocks. We argue that, together with evidence of greater proactive control and more cautious responding for these trials, these findings suggest that older adults strategically recruit greater proactive and reactive control to overcome increased susceptibility to post-stimulus interference. This interpretation is consistent with recruitment of compensatory strategies to compensate for reduced repetition benefit rather than an overall decline on cognitive flexibility.
Large amplitude electron plasma oscillations
Energy Technology Data Exchange (ETDEWEB)
Brodin, G. [Department of Physics, Umeå University, SE-901 87 Umeå (Sweden); Stenflo, L. [Department of Physics, Linköping University, SE-581 83 Linköping (Sweden)
2014-04-01
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.
Analytic Scattering Amplitudes for QCD
Vaman, Diana; Yao, York-Peng
2008-01-01
By analytically continuing QCD scattering amplitudes through specific complexified momenta, one can study and learn about the nature and the consequences of factorization and unitarity. In some cases, when coupled with the largest time equation and gauge invariance requirement, this approach leads to recursion relations, which greatly simplify the construction of multi-gluon scattering amplitudes. The setting for this discussion is in the space-cone gauge.
Loop Integrands for Scattering Amplitudes from the Riemann Sphere
Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr
2015-09-01
The scattering equations on the Riemann sphere give rise to remarkable formulas for tree-level gauge theory and gravity amplitudes. Adamo, Casali, and Skinner conjectured a one-loop formula for supergravity amplitudes based on scattering equations on a torus. We use a residue theorem to transform this into a formula on the Riemann sphere. What emerges is a framework for loop integrands on the Riemann sphere that promises to have a wide application, based on off-shell scattering equations that depend on the loop momentum. We present new formulas, checked explicitly at low points, for supergravity and super-Yang-Mills amplitudes and for n -gon integrands at one loop. Finally, we show that the off-shell scattering equations naturally extend to arbitrary loop order, and we give a proposal for the all-loop integrands for supergravity and planar super-Yang-Mills theory.
Amplitude and phase coding measurements of a liquid crystal television
Laude, V.; Mazé, S.; Chavel, P.; Réfrégier, Ph.
1993-11-01
Presented are amplitude and phase coding, and flicker measurements of liquid crystal panels from the commercially available Epson video projector, for configurations maximizing the contrast. For laser illumination it is found that a contrast as high as 1000 can be achieved, while for white light illumination it is reduced to a still acceptable value of about 60. However it appears that the flicker should be a more limiting factor in practical situations. It is also observed that amplitude and phase modulation are always coupled.
Motivic Amplitudes and Cluster Coordinates
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...
Positive amplitudes in the amplituhedron
Arkani-Hamed, Nima; Hodges, Andrew; Trnka, Jaroslav
2015-08-01
The all-loop integrand for scattering amplitudes in planar 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 inside a co-dimension one surface separating "legal" and "illegal" local singularities of the amplitude. We illustrate this in several simple examples, obtaining new expressions for amplitudes not associated with any triangulations, but following in a more invariant manner from a global view of the positive geometry.
Gang Fang
2009-01-01
Abstract: In this paper, we discuss the upgrade problem of module, and introduce the concepts of the power module, regular power module and uniform power module. We give some results of them? Key words: power group; power module; regular power module; uniform power module
International Nuclear Information System (INIS)
X-ray fractography is a method of analysing the causes of accidental fracture of machine components or structures. Almost all of the previous research on this problem has been carried out using constant amplitude fatigue tests. However, the actual loads on components and structures are usually of variable amplitudes. In this study, X-ray fractography was applied to fatigue fractured surfaces produced by variable amplitude loading. Fatigue tests were carried out on Ni-Cr-Mo steel CT specimens under the conditions of repeated, two-step and multiple-step loading. Residual stresses were measured on the fatigue fractured surface by an X-ray diffraction method. The relationships between residual stress and stress intensity factor or crack propagation rate were studied. They were discussed in terms of the quantitative expressions under constant amplitude loading, proposed by the authors in previous papers. The main results obtained were as follows : (1) It was possible to estimate the crack propagation rate of the fatigue fractured surface under variable amplitude loading by using the relationship between residual stress and stress intensity factor under constant amplitude loading. (2) The compressive residual stress components on the fatigue fractured surface correspond with cyclic softening of the material rather than with compressive plastic deformation at the crack tip. (author)
The face amplitude of spinfoam quantum gravity
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.
International Nuclear Information System (INIS)
A special type of modulation of the injection current of a diode laser is proposed at which the frequency modulation of radiation is not accompanied by the residual amplitude modulation. This method considerably reduces the influence of the diode laser radiation instability on the recorded absorption spectra. This allows a prolonged monitoring of small amounts of impurities in gas analysis by retaining a high sensitivity. Prolonged measurements of absorption spectra are performed at a relative absorption of 8x10-7. By using a 50-cm multipass cell with the optical length of 90 m, the absorption coefficient of 1.2x10-10 cm-1 was detected. As an example, the day evolution of the background concentrations of NO2 molecules was measured in the atmosphere. (laser applications and other topics in quantum electronics)
Thin Photoresponding Elements with Frequency and Amplitude Modulations
Kluso?, Petr
2013-01-01
Nanoscale templated metal oxide thin films undoubtedly appertain to the most extensively studied materials due to their optical and electrochemical properties. Their photo-induced properties arise from the semiconductor nature, especially from the ability of the light quantum absorption followed by the charge carrier generation. In order to produce metal oxide thin layer layers, the liquid sol containing also the templating bodies, and confining nanoparticles, must be coated onto a substrat...
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
Modulated Electron Bunch with Amplitude Front Tilt in an Undulator
Geloni, Gianluca; Saldin, Evgeni
2015-01-01
In a previous paper we discussed the physics of a microbunched electron beam kicked by the dipole field of a corrector magnet by describing the kinematics of coherent undulator radiation after the kick. We demonstrated that the effect of aberration of light supplies the basis for understanding phenomena like the deflection of coherent undulator radiation by a dipole magnet. We illustrated this fact by examining the operation of an XFEL under the steady state assumption, that is a harmonic time dependence. We argued that in this particular case the microbunch front tilt has no objective meaning; in other words, there is no experiment that can discriminate whether an electron beam is endowed with a microbunch front tilt of not. In this paper we extend our considerations to time-dependent phenomena related with a finite electron bunch duration, or SASE mode of operation. We focus our attention on the spatiotemporal distortions of an X-ray pulse. Spatiotemporal coupling arises naturally in coherent undulator radi...
Second-order temporal modulation transfer functions.
Lorenzi, C; Soares, C; Vonner, T
2001-08-01
Detection thresholds were measured for a sinusoidal modulation applied to the modulation depth of a sinusoidally amplitude-modulated (SAM) white noise carrier as a function of the frequency of the modulation applied to the modulation depth (referred to as f'm). The SAM noise acted therefore as a "carrier" stimulus of frequency fm, and sinusoidal modulation of the SAM-noise modulation depth generated two additional components in the modulation spectrum: fm-f'm and fm+f'm. The tracking variable was the modulation depth of the sinusoidal variation applied to the "carrier" modulation depth. The resulting "second-order" temporal modulation transfer functions (TMTFs) measured on four listeners for "carrier" modulation frequencies fm of 16, 64, and 256 Hz display a low-pass segment followed by a plateau. This indicates that sensitivity to fluctuations in the strength of amplitude modulation is best for fluctuation rates f'm below about 2-4 Hz when using broadband noise carriers. Measurements of masked modulation detection thresholds for the lower and upper modulation sideband suggest that this capacity is possibly related to the detection of a beat in the sound's temporal envelope. The results appear qualitatively consistent with the predictions of an envelope detector model consisting of a low-pass filtering stage followed by a decision stage. Unlike listeners' performance, a modulation filterbank model using Q values > or = 2 should predict that second-order modulation detection thresholds should decrease at high values of f'm due to the spectral resolution of the modulation sidebands (in the modulation domain). This suggests that, if such modulation filters do exist, their selectivity is poor. In the latter case, the Q value of modulation filters would have to be less than 2. This estimate of modulation filter selectivity is consistent with the results of a previous study using a modulation-masking paradigm [S. D. Ewert and T. Dau, J. Acoust. Soc. Am. 108, 1181-1196 (2000)]. PMID:11519571
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.
Nonsinglet pentagons and NMHV amplitudes
Directory of Open Access Journals (Sweden)
A.V. Belitsky
2015-07-01
Full Text Available Scattering amplitudes in maximally supersymmetric gauge theory receive a dual description in terms of the expectation value of the super Wilson loop stretched on a null polygonal contour. This makes the analysis amenable to nonperturbative techniques. Presently, we elaborate on a refined form of the operator product expansion in terms of pentagon transitions to compute twist-two contributions to NMHV amplitudes. To start with, we provide a novel derivation of scattering matrices starting from Baxter equations for flux-tube excitations propagating on magnon background. We propose bootstrap equations obeyed by pentagon form factors with nonsinglet quantum numbers with respect to the R-symmetry group and provide solutions to them to all orders in 't Hooft coupling. These are then successfully confronted against available perturbative calculations for NMHV amplitudes to four-loop order.
Scattering Equations and Global Duality of Residues
Sogaard, Mads
2015-01-01
We examine the polynomial form of the scattering equations by means of computational algebraic geometry. The scattering equations are the backbone of the Cachazo-He-Yuan (CHY) representation of the S-matrix. We explain how the Bezoutian matrix facilitates the calculation of amplitudes in the CHY formalism, without explicitly solving the scattering equations or summing over the individual residues. Since for $n$-particle scattering, the size of Bezoutian matrix grows only as $(n-3)\\times(n-3)$, our algorithm is very efficient for analytic and numeric amplitude computations.
Employing Helicity Amplitudes for Resummation
Moult, Ian; Tackmann, Frank J; Waalewijn, Wouter J
2015-01-01
Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of color-ordered helicity amplitudes. Using this basis allows one to seamlessly combine fixed-order helicity amplitudes at any order they are known with a resummation of higher-order logarithmic corrections. In particular, the virtual loop amplitudes can be employed in factorization theorems to make predictions for exclusive jet cross sections without the use of numerical subtraction schemes to handle real-virtual infrared cancellations. We also discuss matching onto SCET in renormalization schemes with helicities in $4$- and $d$-dimensions. To demonstrate that our helicity operator basis is easy to use, we provide an explicit construction of the operator basis, as well as results for the hard m...
Toward complete pion nucleon amplitudes
Energy Technology Data Exchange (ETDEWEB)
Mathieu, Vincent [Indiana University , Bloomington, IN; Danilkin, Igor V. [Jefferson Lab, Newport News, VA; Fernández-Ramírez, Cesar [Jefferson Lab, Newport News, VA; Pennington, Michael R. [Jefferson Lab, Newport News, VA; Schott, Diane M. [George Washington University, Washington, DC; Szczepaniak, Adam P. [Indiana University , Bloomington, IN; Fox, G. [Indiana University, Bloomington, Indiana
2015-10-01
We compare the low-energy partial wave analyses piN scattering with a high-energy data via finite energy sum rules. We construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and reconstruct the real parts using dispersion relations.
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
Absolute frequency references at 1529 nm and 1560 nm using modulation transfer spectroscopy
de Escobar, Y Natali Martinez; Coop, Simon; Vanderbruggen, Thomas; Kaczmarek, Krzysztof T; Mitchell, Morgan W
2015-01-01
We demonstrate a double optical frequency reference (1529 nm and 1560 nm) for the telecom C-band using $^{87}$Rb modulation transfer spectroscopy. The two reference frequencies are defined by the 5S$_{1/2} F=2 \\rightarrow $ 5P$_{3/2} F'=3$ two-level and 5S$_{1/2} F=2 \\rightarrow $ 5P$_{3/2} F'=3 \\rightarrow $ 4D$_{5/2} F"=4$ ladder transitions. We examine the sensitivity of the frequency stabilization to probe power and magnetic field fluctuations, calculate its frequency shift due to residual amplitude modulation, and estimate its shift due to gas collisions. The short-term Allan deviation was estimated from the error signal slope for the two transitions. Our scheme provides a simple and high performing system for references at these important wavelengths. We estimate an absolute accuracy of $\\sim$ 1 kHz is realistic.
Simulation of Digital Modulation Techniques Using MATLAB
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...
Residues and duality for singularity categories of isolated Gorenstein singularities
Murfet, Daniel
2009-01-01
We study Serre duality in the singularity category of an isolated Gorenstein singularity and find an explicit formula for the duality pairing in terms of generalised fractions and residues. For hypersurfaces we recover the residue formula of the string theorists Kapustin and Li. These results are obtained from an explicit construction of complete injective resolutions of maximal Cohen-Macaulay modules.
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 i...
Gauge and Gravity Amplitude Relations
Carrasco, John Joseph M
2015-01-01
In these lectures I talk about simplifications and universalities found in scattering amplitudes for gauge and gravity theories. In contrast to Ward identities, which are understood to arise from familiar symmetries of the classical action, these structures are currently only understood in terms of graphical organizational principles, such as the gauge-theoretic color-kinematics duality and the gravitational double-copy structure, for local representations of multi-loop S-matrix elements. These graphical principles make manifest new relationships in and between gauge and gravity scattering amplitudes. My lectures will focus on arriving at such graphical organizations for generic theories with examples presented from maximal supersymmetry, and their use in unitarity-based multi-loop integrand construction.
Higher Codimension Singularities Constructing Yang-Mills Tree Amplitudes
Rajabi, Sayeh
2011-01-01
Yang-Mills tree-level amplitudes contain singularities of codimension one like collinear and multi-particle factorizations, codimension two such as soft limits, as well as higher codimension singularities. Traditionally, BCFW-like deformations with one complex variable were used to explore collinear and multi-particle channels. Higher codimension singularities need more complex variables to be reached. In this paper, along with a discussion on higher singularities and the role of the global residue theorem in this analysis, we specifically consider soft singularities. This is done by extending Risager's deformation to a $\\mathbb C^2$-plane, i.e., two complex variables. The two-complex-dimensional deformation is then used to recursively construct Yang-Mills tree amplitudes.
Modulation bandwidth of spin torque oscillators under current modulation
Energy Technology Data Exchange (ETDEWEB)
Quinsat, M. [Univ. Grenoble Alpes, F-38054 Grenoble (France); CEA, INAC-SPINTEC, F-38054 Grenoble (France); CNRS, SPINTEC, F-38054 Grenoble (France); CEA-LETI MINATEC-CAMPUS, 17 F-38054 Grenoble (France); Garcia-Sanchez, F.; Jenkins, A. S.; Buda-Prejbeanu, L. D.; Dieny, B.; Ebels, U. [Univ. Grenoble Alpes, F-38054 Grenoble (France); CEA, INAC-SPINTEC, F-38054 Grenoble (France); CNRS, SPINTEC, F-38054 Grenoble (France); Tiberkevich, V. S.; Slavin, A. N. [Department of Physics, Oakland University, Rochester, Michigan 48309 (United States); Zeltser, A.; Katine, J. A. [HGST, San Jose, California 95193 (United States); Cyrille, M.-C. [Univ. Grenoble Alpes, F-38054 Grenoble (France); CEA-LETI MINATEC-CAMPUS, 17 F-38054 Grenoble (France)
2014-10-13
For practical applications of spin torque nano-oscillators (STNO), one of the most critical characteristics is the speed at which an STNO responds to variations of external control parameters, such as current or/and field. Theory predicts that this speed is limited by the amplitude relaxation rate ?{sub p} that determines the timescale over which the amplitude fluctuations are damped out. In this study, this limit is verified experimentally by analyzing the amplitude and frequency noise spectra of the output voltage signal when modulating an STNO by a microwave current. In particular, it is shown that due to the non-isochronous nature of the STNO the amplitude relaxation rate ?{sub p} determines not only the bandwidth of an amplitude modulation, but also the bandwidth of a frequency modulation. The presented experimental technique will be important for the optimisation of the STNO characteristics for applications in telecommunications or/and data storage and is applicable even in the case when the STNO output signal is only several times higher than noise.
Modulations in the light of the firefly
Indian Academy of Sciences (India)
Anurup Gohain Barua
2013-03-01
Continuous light could be produced from the firefly by making it inhale vapours of ethyl acetate. Here we perform such a control experiment on the Indian species of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae), and analyse the light in the microsecond time scale. The amplitude of the continuous train of triangular pulses is apparently altered in accordance with the instantaneous values of a hypothetical signal, which exhibits pulse amplitude modulation (PAM). In addition to sampling in amplitude, this scheme apparently provides sampling in time, representing pulse width modulation (PWM). A Fourier transform spectrum of this waveform shows the ‘carrier’ frequency and the accompanying ‘side bands’.
Superstring amplitudes and contact interactions
International Nuclear Information System (INIS)
We show that scattering amplitudes computed from light-cone superstring field theory are divergent at tree level. The divergences can be eliminated, and supersymmetry restored, by the addition of certain counter terms to the light-cone Hamiltonian. These counter terms have the form of local contact interactions, whose existence we had previously deduced on grounds of vacuum stability, and closure of the super-Poincare algebra. The quartic contact interactions required in Type I and Type IIB superstring theories are constructed in detail. (orig.)
Interpolating axial anomaly induced amplitudes
International Nuclear Information System (INIS)
We propose an interpolating formula for the amplitude induced by the axial anomaly, concentrating on the ?0?*?* transition form factor. Our form factor is constructed by the 'vector meson pole terms' and the 'anomaly terms', in which the anomaly terms can be essentially evaluated by the triangle quark graph. We pay our attention to the anomaly term and make intensive analysis of the existing experimental data, i.e., the electromagnetic ?0 and ? transition form factors. Our result shows that it is essential to use the constituent quark mass instead of the current quark mass in evaluating the anomaly term from the triangle graph. (author)
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)
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.
Similarities of gauge and gravity amplitudes
Bjerrum-Bohr, N E J; Ita, H; Dunbar, David C.; Ita, Harald
2006-01-01
We review recent progress in computations of amplitudes in gauge theory and gravity. We compare the perturbative expansion of amplitudes in N=4 super Yang-Mills and N=8 supergravity and discuss surprising similarities.
Is the effect of tinnitus on auditory steady-state response amplitude mediated by attention?
Directory of Open Access Journals (Sweden)
Eugen Diesch
2012-05-01
Full Text Available Objectives: The amplitude of the auditory steady-state response (ASSR is enhanced in tinnitus. As ASSR ampli¬tude is also enhanced by attention, the effect of tinnitus on ASSR amplitude could be interpreted as an effect of attention mediated by tinnitus. As attention effects on the N1 are signi¬fi¬cantly larger than those on the ASSR, if the effect of tinnitus on ASSR amplitude were due to attention, there should be similar amplitude enhancement effects in tinnitus for the N1 component of the auditory evoked response. Methods: MEG recordings of auditory evoked responses which were previously examined for the ASSR (Diesch et al. 2010 were analysed with respect to the N1m component. Like the ASSR previously, the N1m was analysed in the source domain (source space projection. Stimuli were amplitude-modulated tones with one of three carrier fre¬quen¬cies matching the tinnitus frequency or a surrogate frequency 1½ octaves above the audio¬metric edge frequency in con¬trols, the audiometric edge frequency, and a frequency below the audio¬metric edge Results: In the earlier ASSR study (Diesch et al., 2010, the ASSR amplitude in tinnitus patients, but not in controls, was significantly larger in the (surrogate tinnitus condition than in the edge condition. In the present study, both tinnitus patients and healthy controls show an N1m-amplitude profile identical to the one of ASSR amplitudes in healthy controls. N1m amplitudes elicited by tonal frequencies located at the audiometric edge and at the (surrogate tinnitus frequency are smaller than N1m amplitudes elicited by sub-edge tones and do not differ among each other. Conclusions: There is no N1-amplitude enhancement effect in tinnitus. The enhancement effect of tinnitus on ASSR amplitude cannot be accounted for in terms of attention induced by tinnitus.
International Nuclear Information System (INIS)
Residues of neoasozine in rice grain were determined by neutron activation and colorimetric techniques. Twice application of the chemical before flowering did not lead to increased residue levels while 4-times application resulted in significant increase in the residue level (up to 0.4-0.5 mg/kg). The neutron activation technique was advantageous because of its high sensitivity and the smaller sample amounts required for analysis. The partition ratio of arsenic residues into grain and bran was 73:27 in 100% polished rice. Most of the residue in the bran was transferred to the oilcake fraction. (author)
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)
S. Hal?c?o?lu; Harmanci, A.; G. Güngöro?lu; N. Agayev
2009-01-01
In this note, we introduce abelian modules as a generalization of abelian rings. Let R be an arbitrary ring with identity. A module M is called abelian if, for any m Î M and any a Î R, any idempotent e Î R, mae=mea. We prove that every reduced module, every symmetric module, every semicommutative module and every Armendariz module is abelian. For an abelian ring R, we show that the module MR is abelian iff M[x]R[x] is abelian. We produce an example to show that M[x, ?] need not be abe...
Modulation of resonance cone trajectories by low frequency density fluctuations
International Nuclear Information System (INIS)
It is shown that the previously reported strong linear modulation of lower hybrid waves by low frequency fluctuations is actually a modulation of the lower hybrid cone trajectory. The changing trajectory has the appearance of an amplitude modulation when observed by a stationary probe
Completeness of the scattering amplitudes
Ramm, A G
2006-01-01
Let $f\\in L^2(S^2)$ be an arbitrary fixed function on the unit sphere $S^2$, and $D\\subset \\R^3$ be an arbitrary fixed bounded domain. Let $k>0$ and $\\alpha\\in S^2$ be fixed. It is proved that there exists a potential $q\\in L^2(D)$ such that the corresponding scattering amplitude $A(\\alpha')=A_q(\\alpha')=A_q(\\alpha',\\alpha,k)$ approximates $f(\\alpha')$ with arbitrary high accuracy: $\\|f(\\alpha')-A_q(\\alpha')_{L^2(S^2)}\\|\\leq\\ve$ where $\\ve>0$ is an arbitrarily small fixed number. This means that the set $\\{A_q(\\alpha')\\}_{\\forall q\\in L^2(D)}$ is complete in $L^2(S^2)$. The results can be used for constructing nanotechnologically "smart materials".
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.
Calculation of multi-loop superstring amplitudes
Danilov, G S
2015-01-01
Multi-loop interaction amplitudes in the theory of the closed, oriented superstrings are obtained by the integration of local amplitudes which are represented by a sum of the spinning string local amplitudes. The last local amplitudes are given explicitly through super-Schottky group parameters and interaction vertex coordinates on the $(1|1)$ complex supermanifold. The integration is ambiguous under those replacements of the integration variables which admix Grassmann variables to the boson ones. So the calculation is guided by a preservation of local symmetries of the superstring. The obtained amplitudes are free from divergences and consistent with the world-sheet symmetries. The vacuum amplitude and 1-, 2- and 3-point amplitudes of massless states vanish once the integration over certin modular variables and interaction vertex coordinates.
Local amplitude equation from non-local dynamics
Friedrichs, R; Friedrichs, Rene; Engel, Andreas
2003-01-01
We derive a closed equation for the shape of the free surface of a magnetic fluid subject to an external magnetic field. The equation is strongly non-local due to the long range character of the magnetic interaction. We develop a systematic multiple scale perturbation expansion in which the non-locality is reduced to the occurrence of the Hilbert transform of the surface profile. The resulting third order amplitude equation describing the slow modulation of the basic pattern is shown to be purely local.
Directory of Open Access Journals (Sweden)
S. Hal?c?o?lu
2009-08-01
Full Text Available In this note, we introduce abelian modules as a generalization of abelian rings. Let R be an arbitrary ring with identity. A module M is called abelian if, for any m Î M and any a Î R, any idempotent e Î R, mae=mea. We prove that every reduced module, every symmetric module, every semicommutative module and every Armendariz module is abelian. For an abelian ring R, we show that the module MR is abelian iff M[x]R[x] is abelian. We produce an example to show that M[x, ?] need not be abelian for an abelian module M and an endomorphism ? of the ring R. We also prove that if the module M is abelian, then M is p.p.-module iff M[x] is p.p.-module, M is Baer module iff M[x] is Baer module, M is p.q.-Baer module iff M[x] is p.q.-Baer module.
Study of angular responses of mixed amplitude–phase holographic gratings: shifted Borrmann effect
Carretero López, Luis; Madrigal Madrigal, Roque Fernando; Fimia Gil, Antonio; Blaya Escarre, Salvador; Beléndez Vázquez, Augusto
2000-01-01
We present theoretical results for angular responses of transmitted and diffracted beams in mixed amplitude–phase holographic gratings. Experimental results for gratings recorded in photographic emulsions and developed without a bleaching bath, with diffraction efficiencies of > 20%, are also presented. The model shows an angular shift between minimum transmittance and maximum diffraction efficiency when both index modulation and absorption coefficient modulation are present. Also, the Borrma...
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
Multipole modes in deformed nuclei within the finite amplitude method
Kortelainen, M; Nazarewicz, W
2015-01-01
Background: To access selected excited states of nuclei, within the framework of nuclear density functional theory, the quasiparticle random phase approximation (QRPA) is commonly used. Purpose: We present a computationally efficient, fully self-consistent framework to compute the QRPA transition strength function of an arbitrary multipole operator in axially-deformed superfluid nuclei. Methods: The method is based on the finite amplitude method (FAM) QRPA, allowing fast iterative solution of QRPA equations. A numerical implementation of the FAM-QRPA solver module has been carried out for deformed nuclei. Results: The practical feasibility of the deformed FAM module has been demonstrated. In particular, we calculate the quadrupole and octupole strength in a heavy deformed nucleus $^{240}$Pu, without any truncations in the quasiparticle space. To demonstrate the capability to calculate individual QRPA modes, we also compute low-lying negative-parity collective states in $^{154}$Sm. Conclusions: The new FAM imp...
Xie, Zhenwei; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Akalin, Tahsin; Zhang, Yan
2013-11-01
Terahertz (THz) technology is a developing and promising candidate for biological imaging, security inspection and communications, due to the low photon energy, the high transparency and the broad band properties of the THz radiation. However, a major encountered bottleneck is lack of efficient devices to manipulate the THz wave, especially to modulate the THz wave front. A wave front modulator should allow the optical or electrical control of the spatial transmission (or reflection) of an input THz wave and hence the ability to encode the information in a wave front. Here we propose a spatial THz modulator (STM) to dynamically control the THz wave front with photo-generated carriers. A computer generated THz hologram is projected onto a silicon wafer by a conventional spatial light modulator (SLM). The corresponding photo-generated carrier spatial distribution will be induced, which forms an amplitude hologram to modulate the wave front of the input THz beam. Some special intensity patterns and vortex beams are generated by using this method. This all-optical controllable STM is structure free, high resolution and broadband. It is expected to be widely used in future THz imaging and communication systems.
Razavi-Far, Roozbeh; Zio, Enrico; Palade, Vasile
2014-01-01
This paper focuses on the development of a pre-processing module to generate the latent residuals for sensor fault diagnosis in a doubly fed induction generator of a wind turbine. The pre-processing module bridges a gap between the residual generation and decision modules. The inputs of the pre-processing module are batches of residuals generated by a combined set of observers that are robust to operating point changes. The outputs of the pre-processing module are the latent residuals which a...
International Nuclear Information System (INIS)
Amplitude and temperature dependences of internal friction in molybdenum single crystals of the orientations , , , are studied. The residual resistance ratio of the samples is (1-2)x105. The measurements are carried out at the frequency of 88 kHz in the temperature range 5.9 - 300 K. It has been established that at high temperatures the amplitude-dependent internal friction is due to the process of thermally activated dislocation unpinning from the pinning centres. At low temperatures a maximum is found in the amplitude dependences the height of which decreases with decreasing temperature, but its position does not depend on the temperature. In the same amplitude range a saturation region appears in the modulus defect amplitude dependences. Such a behaviour of the high-amplitude internal friction at low temperatures can not be explained in the framework of the theories present
Attitude Maneuvers of CTS-like Spacecraft Using PD based Constant-Amplitude Inputs
Directory of Open Access Journals (Sweden)
Edward Halawa
2012-01-01
Full Text Available Attitude maneuvers of a Communication Technology Satellite (CTS-like spacecraft using constant-amplitude thrusters is of great importance. The spacecraft consists of a rigid main body and two symmetrical solar panels. When the panels are large, they cannot be treated as rigid bodies anymore. They are supposed to behave structural flexibility. To discrete their motion, the finite element method is followed. Under constant-amplitude thrusts, steady-state attitude angle oscillations may occur in large amplitude after the maneuvers. Since, the spacecraft should point to the earth precisely, these oscillations must be reduced into small permissible values. To reduce residual attitude angle oscillations, Proportional Derivative (PD based constant-amplitude input shaping logic is proposed to determine time locations of thruster switching. Then, under such inputs, attitude maneuvers of the spacecraft are simulated numerically. Results of simulations show that the precise orientation of the satellite can be achieved.
Application of matched filtering to identify behavioral modulation of brain oscillations.
Stamoulis, Catherine; Richardson, Andrew G
2010-08-01
Brain oscillations modulated by motor behaviors are coupled to steady-state and other potentially unrelated to movement oscillations, with energy in the same frequency bands as the signals of interest. We applied matched filtering, a quasi-optimum signal detection technique, to decouple and extract movement-related signals from local field potentials (LFPs) recorded in monkey motor cortical areas during the execution of a visually instructed reach-out task. Using a matched-filterbank, we examined coupling and interference of pre-movement and initial steady-state oscillations with movement-induced signals. Once these signal contributions were eliminated, we were able to identify significant correlations of the residual signals with behavioral parameters, which appeared attenuated by pre-movement signal interference in the raw LFPs. Specifically, the maximum and minimum amplitudes of filtered LFPs were directly modulated by peak movement velocity and micro-movements, respectively, identified in recorded hand velocity profiles. In addition, we identified phase correlations between signals during the delay (when the instructional cue was presented) and movement intervals, as well as modulation of LFP phase by movement direction. For pairs of orthogonal movement directions, corresponding LFP signals were consistently out of phase. Finally, ?-band energy which is typically reduced during movement execution, possibly partly due to destructive interference between the modulated by behavior signal and unrelated oscillations, appeared to be recovered in the filtered signals. PMID:19424783
Flux Modulation in the Electrodynamic Loudspeaker
DEFF Research Database (Denmark)
Halvorsen, Morten; Tinggaard, Carsten
2015-01-01
This paper discusses the effect of flux modulation in the electrodynamic loudspeaker with main focus on the effect on the force factor. A measurement setup to measure the AC flux modulation with static voice coil is explained and the measurements shows good consistency with FEA simulations. Measurements of the generated AC flux modulation shows, that eddy currents are the main source to magnetic losses in form of phase lag and amplitude changes. Use of a copper cap shows a decrease in flux modulation amplitude at the expense of increased power losses. Finally, simulations show that there is a high dependency between the generated AC flux modulation from the voice coil and the AC force factor change.
Venugopal Manju; Kizhakke Kodiyath Gopika; Pitchai Muthu Arivudai Nambi
2014-01-01
Amplitude modulations in the speech convey important acoustic information for speech perception. Auditory steady state response (ASSR) is thought to be physiological correlate of amplitude modulation perception. Limited research is available exploring association between ASSR and modulation detection ability as well as speech perception. Correlation of modulation detection thresholds (MDT) and speech perception in noise with ASSR was investigated in twofold experiments. 30 normal hearing indi...
S-Duality and Helicity Amplitudes
Colwell, Kitran
2015-01-01
We examine interacting Abelian theories at low energies and show that holomorphically normalized photon helicity amplitudes transform into dual amplitudes under SL(2,Z) as modular forms with weights that depend on the number of positive and negative helicity photons and on the number of internal photon lines. Moreover, canonically normalized helicity amplitudes transform by a phase, so that even though the amplitudes are not duality invariant, their squares are duality invariant. We explicitly verify the duality transformation at one loop by comparing the amplitudes in the case of an electron and the dyon that is its SL(2,Z) image, and extend the invariance of squared amplitudes order by order in perturbation theory. We demonstrate that S-duality is property of all low-energy effective Abelian theories with electric and/or magnetic charges and see how the duality generically breaks down at high energies.
Neutron scattering amplitude of natural Gd
International Nuclear Information System (INIS)
The measurement of scattering amplitude in the region of epithermal neutrons of natural Gd was carried out over wide neutron energy range. The obtained amplitude was a constant value of (0.95 +- 0.02) x 10-12cm in the measured energy range, except the resonance region. This value is the normal scattering amplitude of natural Gd. Two methods were employed for the measurement. The one is to obtain the amplitude by comparison of the magnetic scattering intensity with the nuclear scattering of diffraction line of a Gd single crystal, and the other is to determine the amplitude from the intensity ratio of the fundamental lattice diffraction line and the super lattice diffraction line of GdZn. Measurements were performed for metallic Gd and GdZn. The variation of scattering amplitude due to the neutron abnormal scattering was observed near the resonance at 2.64 eV. (Kato, T.)
Sivokon', V. P.; Bogdanov, V. V.; Druzhin, G. I.; Cherneva, N. V.; Kubyshkin, A. V.; Sannikov, D. V.; Agranat, I. V.
2014-11-01
Analysis of the experimental data obtained at Paratunka observatory (53.02° N, 158.65° E; L = 2.3) has revealed a nonstandard form of whistlers involving spectral lines that are symmetric with respect to the whistler. We have shown that this form is most likely due to the amplitude modulation of whistlers by electromagnetic pulses with a length of around 1 s and carrier frequency of around 1.1 kHz. We have suggested that these pulses could be emitted by the auroral electrojet modified by heating radiation from the HAARP facility (62.30° N, 145.30° W; L > 4.2).
Effect of residual stresses on the fatigue crack propagation in welded joints
Gubeljak, Nenad; Predan, Jožef; Pippan, Reinhard; Oblak, Maks
2012-01-01
The effect of residual stress on the fatigue crack growth was investigated forcyclic tension. Three-point bend specimens were used with through thicknessnotches at the center line of the welded joint. The experiments were performed for different load amplitudes and load ratios under conditions of small-scale yielding. The influence of the residual stresses on fatigue crack growth was estimated by experimentally observed fatigue crack growth rate and measurement of residual stresses at the sur...
Influence of beam loading on emittance growth induced by RF amplitude noise
International Nuclear Information System (INIS)
Both phase and amplitude noise can spread the bunch longitudinal emittance toward the rf bucket boundary. This paper shows that the modulation transfer functions of a cavity detuned to compensate beam loading serve to increase the emittance growth rate. The effect of fast feedback on the transfer function is also discussed. (Author) 8 refs., 3 figs
Agricultural pesticide residues
International Nuclear Information System (INIS)
The utilization of tracer techniques in the study of agricultural pesticide residues is reviewed under the following headings: lysimeter experiments, micro-ecosystems, translocation in soil, degradation of pesticides in soil, biological availability of soil-applied substances, bound residues in the soil, use of macro- and microautography, double and triple labelling, use of tracer labelling in animal experiments. (U.K.)
This indicator describes the number of pesticide residues detected in fruits, vegetables, grains, meat, and dairy products from across the country and the number of residues exceeding the EPA tolerance for a given pesticide-commodity pair from 1994 to 2009. This information pr...
Understanding and Ameliorating Non-Linear Phase and Amplitude Responses in AMCW Lidar
Directory of Open Access Journals (Sweden)
John P. Godbaz
2011-12-01
Full Text Available Amplitude modulated continuous wave (AMCW lidar systems commonly suffer from non-linear phase and amplitude responses due to a number of known factors such as aliasing and multipath inteference. In order to produce useful range and intensity information it is necessary to remove these perturbations from the measurements. We review the known causes of non-linearity, namely aliasing, temporal variation in correlation waveform shape and mixed pixels/multipath inteference. We also introduce other sources of non-linearity, including crosstalk, modulation waveform envelope decay and non-circularly symmetric noise statistics, that have been ignored in the literature. An experimental study is conducted to evaluate techniques for mitigation of non-linearity, and it is found that harmonic cancellation provides a significant improvement in phase and amplitude linearity.
Paralleled Phase Shifted Carrier Pulse Width Modulation (PSCPWM) Schemes - A Fundamental Analysis
DEFF Research Database (Denmark)
Christensen, Frank Schwartz; Frederiksen, Thomas Mansachs; Nielsen, Karsten
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.
Modulation masking produced by second-order modulators
DEFF Research Database (Denmark)
Füllgrabe, Christian; Moore, Brian C.J.; Demany, Laurent; Ewert, Stephan; Sheft, Stanley; Lorenzi, Christian
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 mas...
International Nuclear Information System (INIS)
The topic of solid residues is specifically of great interest and concern for the authorities, institutions and community that identify in them a true threat against the human health and the atmosphere in the related with the aesthetic deterioration of the urban centers and of the natural landscape; in the proliferation of vectorial transmitters of illnesses and the effect on the biodiversity. Inside the wide spectrum of topics that they keep relationship with the environmental protection, the inadequate handling of solid residues and residues dangerous squatter an important line in the definition of political and practical environmentally sustainable. The industrial development and the population's growth have originated a continuous increase in the production of solid residues; of equal it forms, their composition day after day is more heterogeneous. The base for the good handling includes the appropriate intervention of the different stages of an integral administration of residues, which include the separation in the source, the gathering, the handling, the use, treatment, final disposition and the institutional organization of the administration. The topic of the dangerous residues generates more expectation. These residues understand from those of pathogen type that are generated in the establishments of health that of hospital attention, until those of combustible, inflammable type, explosive, radio-active, volatile, corrosive, reagent or toxic, associated to numerous industrial processes, common in our countries in development
Energy Technology Data Exchange (ETDEWEB)
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.
Helicity amplitudes for matter-coupled gravity
International Nuclear Information System (INIS)
The Weyl-van der Waerden spinor formalism is applied to the evaluation of helicity invariant amplitudes in the framework of linearized gravitation. The graviton couplings to spin-0, 1 -2, 1, and 3 -2 particles are given, and, to exhibit the reach of this method, the helicity amplitudes for the process electron + positron ? photon + graviton are obtained. (author)
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.)
Validity of certain soft photon amplitudes
Welsh, M; Welsh, Mark; Fearing, Harold W
1996-01-01
Certain soft photon amplitudes which have been recently suggested as alternatives to the usual Low form of the soft photon approximation are studied and it is demonstrated that problems exist in their relation to the corresponding non-radiative amplitude. The non-radiative amplitude, which is an input to soft photon calculations, is in certain cases required to be evaluated outside of its physical phase space region. Also, for the case of two-body identical particle bremsstrahlung processes, the symmetrized or antisymmetrized form of these soft photon amplitudes cannot be written in terms of the symmetrized or antisymmetrized amplitude for the non-radiative process. It is found that the usual Low form of the soft photon theorem is essentially unaffected by these problems.
High amplitude events in microchannel plates
Energy Technology Data Exchange (ETDEWEB)
Siegmund, O.H.W.; Lammert, P.; Vallerga, J.V.; Priedhorsky, W.; Smith, B.W.
1989-02-01
Measurements have been made to determine the characteristics of high amplitude events in microchannel plates (MCP's). The background pulse amplitude spectrum is found to extend to >30x the MCP modal gain. The majority of the background events are initiated by /sup 40/K beta decay in the MCP glass. However, up to 4% of the events are due to cosmic ray events. Comparison of background pulse amplitude spectra for horizontal, and vertical MCP orientations suggests that the largest events are predominantly cosmic ray induced. Anticoincidence measurements confirm this result. A model describing the /sup 40/K beta decay and cosmic ray interactions in the MCP predicts spectra in accord with these observations. The authors have also determined the response of MCP's when subjected to simultaneous multiphon input. This shows that pulse amplitudes many times the modal gain are possible even though the response becomes nonlinear at high amplitudes.
High amplitude events in microchannel plates
International Nuclear Information System (INIS)
Measurements have been made to determine the characteristics of high amplitude events in microchannel plates (MCP's). The background pulse amplitude spectrum is found to extend to >30x the MCP modal gain. The majority of the background events are initiated by /sup 40/K beta decay in the MCP glass. However, up to 4% of the events are due to cosmic ray events. Comparison of background pulse amplitude spectra for horizontal, and vertical MCP orientations suggests that the largest events are predominantly cosmic ray induced. Anticoincidence measurements confirm this result. A model describing the /sup 40/K beta decay and cosmic ray interactions in the MCP predicts spectra in accord with these observations. The authors have also determined the response of MCP's when subjected to simultaneous multiphon input. This shows that pulse amplitudes many times the modal gain are possible even though the response becomes nonlinear at high amplitudes
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
Modulation characteristics of the Epson liquid crystal television
Kirsch, James C.; Gregory, Don A.; Thie, Melissa W.; Jones, Brian K.
1992-05-01
The amplitude- and phase-modulating properties of liquid crystal televisions (LCTVs) are becoming increasingly well known. The Epson Crystal Image video projector is a relatively new TV and uses three liquid crystal panels to encode the red, green, and blue components of the video signal onto the projector light. These panels can be removed for use in optical systems. We present the results from measurements of the phase- and amplitude-modulation properties of one of these LCTV panels.
Online tracking of instantaneous frequency and amplitude of dynamical system response
Frank Pai, P.
2010-05-01
This paper presents a sliding-window tracking (SWT) method for accurate tracking of the instantaneous frequency and amplitude of arbitrary dynamic response by processing only three (or more) most recent data points. Teager-Kaiser algorithm (TKA) is a well-known four-point method for online tracking of frequency and amplitude. Because finite difference is used in TKA, its accuracy is easily destroyed by measurement and/or signal-processing noise. Moreover, because TKA assumes the processed signal to be a pure harmonic, any moving average in the signal can destroy the accuracy of TKA. On the other hand, because SWT uses a constant and a pair of windowed regular harmonics to fit the data and estimate the instantaneous frequency and amplitude, the influence of any moving average is eliminated. Moreover, noise filtering is an implicit capability of SWT when more than three data points are used, and this capability increases with the number of processed data points. To compare the accuracy of SWT and TKA, Hilbert-Huang transform is used to extract accurate time-varying frequencies and amplitudes by processing the whole data set without assuming the signal to be harmonic. Frequency and amplitude trackings of different amplitude- and frequency-modulated signals, vibrato in music, and nonlinear stationary and non-stationary dynamic signals are studied. Results show that SWT is more accurate, robust, and versatile than TKA for online tracking of frequency and amplitude.
Biodigestion of cellulose residues
Energy Technology Data Exchange (ETDEWEB)
Ostrovski, C.M.
1981-01-01
A review and discussion on the mechanical and chemical pretreatment of cellulosic materials to enhance biodegradation resulting in excellent CH/sub 4/ production and organic residue decomposition. (Refs. 12).
Characterization of Hospital Residuals
International Nuclear Information System (INIS)
The main objective of this investigation is the characterization of the solid residuals. A description of the handling of the liquid and gassy waste generated in hospitals is also given, identifying the source where they originate. To achieve the proposed objective the work was divided in three stages: The first one was the planning and the coordination with each hospital center, in this way, to determine the schedule of gathering of the waste can be possible. In the second stage a fieldwork was made; it consisted in gathering the quantitative and qualitative information of the general state of the handling of residuals. In the third and last stage, the information previously obtained was organized to express the results as the production rate per day by bed, generation of solid residuals for sampled services, type of solid residuals and density of the same ones. With the obtained results, approaches are settled down to either determine design parameters for final disposition whether for incineration, trituration, sanitary filler or recycling of some materials, and storage politics of the solid residuals that allow to determine the gathering frequency. The study concludes that it is necessary to improve the conditions of the residuals handling in some aspects, to provide the cleaning personnel of the equipment for gathering disposition and of security, minimum to carry out this work efficiently, and to maintain a control of all the dangerous waste, like sharp or polluted materials. In this way, an appreciable reduction is guaranteed in the impact on the atmosphere. (Author)
Power-Stepped HF Cross Modulation Experiments at HAARP
Greene, S.; Moore, R. C.; Langston, J. S.
2013-12-01
High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. In this paper, we apply experimental observations of HF cross-modulation to the related problem of ELF/VLF wave generation. HF cross-modulation measurements are used to evaluate the efficiency of ionospheric conductivity modulation during power-stepped modulated HF heating experiments. The results are compared to previously published dependencies of ELF/VLF wave amplitude on HF peak power. The experiments were performed during the March 2013 campaign at the High Frequency Active Auroral Research Program (HAARP) Observatory. HAARP was operated in a dual-beam transmission format: the first beam heated the ionosphere using sinusoidal amplitude modulation while the second beam broadcast a series of low-power probe pulses. The peak power of the modulating beam was incremented in 1-dB steps. We compare the minimum and maximum cross-modulation effect and the amplitude of the resulting cross-modulation waveform to the expected power-law dependence of ELF/VLF wave amplitude on HF power.
High Energy Hadron Spin Flip Amplitude
Selyugin, O V
2015-01-01
The high energy part of the hadron spin flip amplitude is examined in the framework of the new high energy general structure (HEGS) model of the elastic hadron scattering at high energies. The different forms of the hadron spin flip amplitude are compared in the impact parameters representation. It is shown that the existing experimental data of the proton-proton and proton-antiproton elastic scattering at high energy in the region of the diffraction minimum and at large momentum transfer give support in the presence of the energy-independent part of the hadron spin flip amplitude with the momentum dependence proposed in the works by Galynskii-Kuraev.
Alahmadi, Adel; Jain, S. K.; Leroy, André
2012-01-01
We study the class of ADS rings and modules introduced by Fuchs. We give some connections between this notion and classical notions such as injectivity and quasi-continuity. A simple ring R such that R is ADS as a right R-module must be either right self-injective or indecomposable as a right R-module. Under certain conditions we can construct a unique ADS hull up to isomorphism. We introduce the concept of completely ADS modules and characterize completely ADS semiperfect r...
Instantaneous modulation of gamma oscillation frequency by balancing excitation with inhibition
Atallah, Bassam V; Scanziani, Massimo
2009-01-01
Neurons recruited for local computations exhibit rhythmic activity at gamma frequencies. The amplitude and frequency of these oscillations are continuously modulated depending on stimulus and behavioral state. This modulation is believed to crucially control information flow across cortical areas. Here we report that in the rat hippocampus gamma oscillation amplitude and frequency vary rapidly, from one cycle to the next. Strikingly, the amplitude of one oscillation predicts the interval to t...
Hadamard Coded Modulation for Visible Light Communications
Noshad, Mohammad; Brandt-Pearce, Maite
2014-01-01
Visible light communication (VLC) systems using the indoor lighting system to also provide downlink communications require high average optical powers in order to satisfy the illumination needs. This can cause high amplitude signals common in higher-order modulation schemes to be clipped by the peak power constraint of the light emitting diode (LED) and lead to high signal distortion. In this paper we introduce Hadamard coded modulation (HCM) to achieve low error probabiliti...
Modulation instability of an electrostatic plasma wave
International Nuclear Information System (INIS)
A four wave interaction among a Langmuir wave, its upper and lower sideband waves, and a low frequency ion sound wave is formulated in terms of a nonlinear dispersion relation to investigate the modulational instability of the wave packet of the Langmuir wave. The nonlinear dispersion relation is converted to a nonlinear Schroedinger type of equation and is analyzed to investigate the slow evolution of the wave amplitude. The instability criterion and the growth rate for the modulational instability are obtained. (author)
Temporary Suppression of Tinnitus by Modulated Sounds
Reavis, Kelly M.; Rothholtz, Vanessa S.; Tang, Qing; Carroll, Jeff A.; Djalilian, Hamid; Zeng, Fan-Gang
2012-01-01
Despite high prevalence of tinnitus and its impact on quality life, there is no cure for tinnitus at present. Here, we report an effective means to temporarily suppress tinnitus by amplitude- and frequency-modulated tones. We systematically explored the interaction between subjective tinnitus and 17 external sounds in 20 chronic tinnitus sufferers. The external sounds included traditionally used unmodulated stimuli such as pure tones and white noise and dynamically modulated stimuli known to ...
Energy Technology Data Exchange (ETDEWEB)
Saat, N. K. [Department of Physics, Faculty of Science, University Putra Malaysia (Malaysia); Dean, P.; Khanna, S. P.; Salih, M.; Linfield, E. H.; Davies, A. G. [School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom)
2015-04-24
We demonstrate new switching circuit for difference-intensity THz quantum cascade laser (QCL) imaging by amplitude modulation and lock in detection. The switching circuit is designed to improve the frequency modulation so that it can stably lock the amplitude modulation of the QCL and the detector output. The combination of a voltage divider and a buffer in switching circuit to quickly switch the amplitude of the QCL biases of 15.8 V and 17.2 V is successfully to increase the frequency modulation up to ?100 Hz.
Phase-only spatial light modulation by the reverse phase contrast method
DEFF Research Database (Denmark)
Glückstad, J.; Mogensen, P.C.
2002-01-01
A new approach to phase-only spatial light modulation is proposed in which a given amplitude pattern can be converted into a spatially identical binary phase pattern. A spatial filtering approach is applied to transform spatial amplitude modulation into spatial phase modulation using the Reverse Phase Contrast (RPC) method. The analytical method for achieving this is outlined and experimental results are shown for the generation of a binary phase-only distribution using an amplitude spatial light modulator and a phase-only spatial filter.
Relative phase between the J/? ? ?? and ? ? amplitudes
International Nuclear Information System (INIS)
It is shown that the study of the ?-?0 interference pattern in the J/? ? (?0 + ?)? ? ?+?-? decay provides evidence for the large (nearly 90 deg) relative phase between the one-photon and the three-gluon decay amplitudes
MHV-Vertices for Gravity Amplitudes
Bjerrum-Bohr, N E J; Ita, H; Perkins, W B; Risager, K; Dunbar, David C.; Ita, Harald; Perkins, Warren B.; Risager, Kasper
2006-01-01
We obtain a CSW-style formalism for calculating graviton scattering amplitudes and prove its validity through the use of a special type of BCFW-like parameter shift. The procedure is also illustrated with explicit examples.
Regge amplitudes with crossing and unitarity
International Nuclear Information System (INIS)
A new crossing symmetric. Sommerfeld-Watson transformation is reported that produces an amplitude which moreover has the expected Regge asymptotic behaviour and the correct support of the Mandelstam double spectral functions
An analysis of heavy ion scattering amplitudes
International Nuclear Information System (INIS)
A heurisht method is derived for the analysis of light heavy ion systems. It consists in splitting an oscillatory amplitude into subamplitudes each of them being smooth, at least in modulus. Applications are given
Off-shell Amplitudes in Superstring Theory
Sen, Ashoke
2014-01-01
Computing the renormalized masses and S-matrix elements in string theory, involving states whose masses are not protected from quantum corrections, requires defining off-shell amplitude with certain factorization properties. While in the bosonic string theory one can in principle construct such an amplitude from string field theory, there is no fully consistent field theory for superstring and heterotic string theory. In this paper we give a practical construction of off-shell amplitudes satisfying the desired factorization property using the formalism of picture changing operators. We describe a systematic procedure for dealing with the spurious singularities of the integration measure that we encounter when the supermoduli space is not holomorphically projected. This procedure is also useful for computing on-shell amplitudes, as we demonstrate by computing the effect of Fayet-Iliopoulos D-terms in four dimensional heterotic string theory compactifications using this formalism.
The singular behavior of massive QCD amplitudes
International Nuclear Information System (INIS)
We discuss the structure of infrared singularities in on-shell QCD amplitudes with massive partons and present a general factorization formula in the limit of small parton masses. The factorization formula gives rise to an all-order exponentiation of both, the soft poles in dimensional regularization and the large collinear logarithms of the parton masses. Moreover, it provides a universal relation between any on-shell amplitude with massive external partons and its corresponding massless amplitude. For the form factor of a heavy quark we present explicit results including the fixed-order expansion up to three loops in the small mass limit. For general scattering processes we show how our constructive method applies to the computation of all singularities as well as the constant (mass-independent) terms of a generic massive n-parton QCD amplitude up to the next-to-next-to-leading order corrections. (orig.)
Small amplitude quasi-breathers and oscillons
Fodor, Gyula; Horváth, Zalán; Lukács, Árpád
2008-01-01
Quasi-breathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in Phys. Rev. D. 74, 124003 (2006). QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in $D$ spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, $D_{crit}=4$, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.
Frequency-to-amplitude converter: A concept
Stewart, C. H.
1972-01-01
Circuit allows direct frequency to amplitude conversion without special counters and discriminators and provides for individual or simultaneous emphasis of high or low frequencies. Circuit is simple, small, light weight, and versatile in its frequency range and region of conversion.
Amplitudes for left-handed strings
Siegel, W
2015-01-01
We consider a class of string-like models introduced previously where all modes are left-handed, all states are massless, T-duality is manifest, and only a finite number of orders in the string tension can appear. These theories arise from standard string theories by a singular gauge limit and associated change in worldsheet boundary conditions. In this paper we show how to calculate amplitudes by using the gauge parameter as an infrared regulator. The amplitudes produce the Cachazo-He-Yuan delta-functions after some modular integration; the Mason-Skinner string-like action and amplitudes arise from the zero-tension (infinite-slope) limit. However, without the limit the amplitudes have the same problems as found in the Mason-Skinner formalism.
Off-shell amplitudes in superstring theory
Energy Technology Data Exchange (ETDEWEB)
Sen, Ashoke [Harish-Chandra Research Institute, Chhatnag Road, Jhusi, Allahabad, 211019 (India)
2015-04-01
Computing the renormalized masses and S-matrix elements in string theory, involving states whose masses are not protected from quantum corrections, requires defining off-shell amplitude with certain factorization properties. While in the bosonic string theory one can in principle construct such an amplitude from string field theory, there is no fully consistent field theory for type II and heterotic string theory. In this paper we give a practical construction of off-shell amplitudes satisfying the desired factorization property using the formalism of picture changing operators. We describe a systematic procedure for dealing with the spurious singularities of the integration measure that we encounter in superstring perturbation theory. This procedure is also useful for computing on-shell amplitudes, as we demonstrate by computing the effect of Fayet-Iliopoulos D-terms in four dimensional heterotic string theory compactifications using this formalism. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
A hybrid simulation incorporating multiple modulation techniques
Gardner, C. R.
A hybrid simulation developed for comparison and analysis of several diverse modulation techniques is described. The inherent purpose of the simulation is to provide a highly versatile model of a LOS digital transceiver. When coupled with band spectral limiting and a LOS channel model, the combination provides a highly effective tool for performance appraisal of most state-of-the-art digital modulation techniques presently employed in LOS microwave communications. User selectable modulation schemes include Quadrature Partial Response (QPR), Quadrature Amplitude Modulation (QAM), Phase Shift Keying (PSK), and Minimum Shift Keying (MSK) at applicably variable modulation levels and bit rates. A brief description of each modulation technique is presented along with specific requirements for integration into a hybrid simulated digital transceiver.
Amplitude Dependent Damping in Vinyl Polymers
Povolo, F.; Goyanes, S.
1996-01-01
The damping behaviour of several vinyl polymers-poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), polystyrene (PS) and impact polystyrene (PSi)–was studied both as a funtion of temperature and strain amplitude. The measurements were performed from room temperature up to the glass transition temperature and shows amplitude dependence at frequencies of the order of 50 kHz. The data are interpreted in terms of a hyperbolic sine stress dependence of the strain rate, including an effec...
Path integral evaluation of Dbrane amplitudes
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.
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.)
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)
Amplitude-Based Approach to Evidence Accumulation
Hanson, A. J.
2013-01-01
We point out the need to use probability amplitudes rather than probabilities to model evidence accumulation in decision processes involving real physical sensors. Optical information processing systems are given as typical examples of systems that naturally gather evidence in this manner. We derive a new, amplitude-based generalization of the Hough transform technique used for object recognition in machine vision. We argue that one should use complex Hough accumulators and ...
Microwave Imaging using Amplitude-only Data
Rubæk, Tonny; Zhurbenko, Vitaliy
2010-01-01
This paper discuss how the performance of an imaging system is affected when the phase information of the measurements are removed from the data, leaving only amplitude information as input for the imaging algorithm. Simulated data are used for this purpose, and the images resulting from using amplitude-only data are compared with images obtained using the same data sets in which the phase information has been retained. In addition to this, some modifications for the imaging algorithm is pres...
A new approach for analytic amplitude calculations
International Nuclear Information System (INIS)
We present a method for the 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 an algebra manipulating code for a computer
Computation of one-loop gluon amplitudes
Energy Technology Data Exchange (ETDEWEB)
Biedermann, Benedikt [Humboldt University, Berlin (Germany)
2010-07-01
A numerical approach for the computation of QCD one-loop gluon amplitudes in pure gauge theory is presented. Using generalized unitarity, we compute the coefficients of the occuring scalar one-loop integrals. As basic ingredient, the Berends-Giele recursion is used to construct on-shell tree amplitudes. The performance of the program is explored and the algorithms of the implemented methods are explained.
Amplitude distribution of eigenfunctions in mixed systems
International Nuclear Information System (INIS)
We study the amplitude distribution of irregular eigenfunctions in systems with mixed classical phase space. For an appropriately restricted random wave model, a theoretical prediction for the amplitude distribution is derived and a good agreement with numerical computations for the family of limacon billiards is found. The natural extension of our result to more general systems, e.g. with a potential, is also discussed. (author)
Multiparticle tree amplitudes in scalar field theory
Brandt, F T; Brandt, Fernando T; Frenkel, Josif
1996-01-01
Following an argument advanced by Feynman, we consider a method for obtaining the effective action which generates the sum of tree diagrams with external physical particles. This technique is applied, in the unbroken \\lambda \\phi^4 theory, to the derivation of the threshold amplitude for the production of n scalar particles by n initial particles. The leading contributions to the tree amplitude, which become singular in the threshold limit, exhibit a factorial growth with n.
Microwave Imaging using Amplitude-only Data
DEFF Research Database (Denmark)
Rubæk, Tonny; Zhurbenko, Vitaliy
2010-01-01
This paper discuss how the performance of an imaging system is affected when the phase information of the measurements are removed from the data, leaving only amplitude information as input for the imaging algorithm. Simulated data are used for this purpose, and the images resulting from using amplitude-only data are compared with images obtained using the same data sets in which the phase information has been retained. In addition to this, some modifications for the imaging algorithm is present...
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)
International Nuclear Information System (INIS)
The IAEA attaches great importance to the dissemination of information that can assist Member States in the development, implementation, maintenance and continuous improvement of systems, programmes and activities that support the nuclear fuel cycle and nuclear applications, and that address the legacy of past practices and accidents. However, radioactive residues are found not only in nuclear fuel cycle activities, but also in a range of other industrial activities, including: - Mining and milling of metalliferous and non-metallic ores; - Production of non-nuclear fuels, including coal, oil and gas; - Extraction and purification of water (e.g. in the generation of geothermal energy, as drinking and industrial process water; in paper and pulp manufacturing processes); - Production of industrial minerals, including phosphate, clay and building materials; - Use of radionuclides, such as thorium, for properties other than their radioactivity. Naturally occurring radioactive material (NORM) may lead to exposures at some stage of these processes and in the use or reuse of products, residues or wastes. Several IAEA publications address NORM issues with a special focus on some of the more relevant industrial operations. This publication attempts to provide guidance on managing residues arising from different NORM type industries, and on pertinent residue management strategies and technologies, to help Member States gain perspectives on the management of NORM residues
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)
Higher-order solitons in amplitude-disordered waveguide arrays
International Nuclear Information System (INIS)
We investigate the existence and stability of different families of spatial solitons in optical waveguide arrays whose amplitudes obey a disordered distribution. The competition between focusing nonlinearity and linearly disordered refractive index modulation results in the formation of spatial localized nonlinear states. Solitons originating from Anderson modes with few nodes are robust during propagation. While multi-peaked solitons with in-phase neighboring components are completely unstable, multipole-mode solitons whose neighboring components are out-of-phase can propagate stably in wide parameter regions provided that their power exceeds a critical value. Our findings, thus, provide the first example of stable higher-order nonlinear states in disordered systems. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
Kalaitzis, Alfredo A
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 variance. We decompose the residual variance into its components through a generalized eigenvalue problem, which we call residual component analysis (RCA). We show that canonical covariates analysis (CCA) is a special case of our algorithm and explore a range of new algorithms that arise from the framework. We illustrate the ideas on a gene expression time series data set and the recovery of human pose from silhouette.
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...
Decomposition of residue currents
Andersson, Mats
2007-01-01
Given a submodule $J\\subset \\mathcal O_0^{\\oplus r}$ and a free resolution of $J$ one can define a certain vector valued residue current whose annihilator is $J$. We make a decomposition of the current with respect to Ass$(J)$ that correspond to a primary decomposition of $J$. As a tool we introduce a class of currents that includes usual residue and principal value currents; in particular these currents admit a certain type of restriction to analytic varieties and more generally to constructible sets.
Residues requiring surveillance
International Nuclear Information System (INIS)
The paper compares the Austrian and German regulations concerning protection of the public against exposures from residues. Despite similarities in the terms the European Basic Safety Standards were implemented in quite different ways in both countries. This refers as well to the graded approach of regulatory control as to the positive lists of residues contained in both national legislations. More similar are the procedures of release from regulatory control. Based on practical experience mainly from Germany some comments and statements concerning the applicability of the existing regulations are derived. As far as the newly proposed European Basic Safety Standards touching the issues discussed, some assessments are given, too. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Ezeilo, A.N.; Webster, G.A. [Imperial College, London (United Kingdom); Webster, P.J. [Salford Univ. (United Kingdom)
1997-04-01
Because neutrons can penetrate distances of up to 50 mm in most engineering materials, this makes them unique for establishing residual-stress distributions non-destructively. D1A is particularly suited for through-surface measurements as it does not suffer from instrumental surface aberrations commonly found on multidetector instruments, while D20 is best for fast internal-strain scanning. Two examples for residual-stress measurements in a shot-peened material, and in a weld are presented to demonstrate the attractive features of both instruments. (author).
A.C. modulation technique for the angular correlation measurements
International Nuclear Information System (INIS)
On the basis of stochastic models for random pulses occurring in correlation measurements a new method of a.c. modulation is described for converting signal variations into an amplitude modulation which can be analysed with a coherent detector for filtering the background by several orders of magnitude. (author)
A Ser residue influences the structure and stability of a Pro-kinked transmembrane helix dimer
DEFF Research Database (Denmark)
Weber, Mathias; Tome, Lydia; Otzen, Daniel; Schneider, Dirk
2012-01-01
When localized adjacent to a Pro-kink, Thr and Ser residues can form hydrogen bonds between their polar hydroxyl group and a backbone carbonyl oxygen and thereby modulate the actual bending angle of a distorted transmembrane ?-helix. We have used the homo-dimeric transmembrane cytochrome b(559)' to analyze the potential role of a highly conserved Ser residue for assembly and stabilization of transmembrane proteins. Mutation of the conserved Ser residue to Ala resulted in altered heme binding pro...
Attenuation of ground-motion spectral amplitudes in southeastern Australia
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.
Neural Representations of Complex Temporal Modulations in the Human Auditory Cortex
Ding, Nai; Simon, Jonathan Z.
2009-01-01
Natural sounds such as speech contain multiple levels and multiple types of temporal modulations. Because of nonlinearities of the auditory system, however, the neural response to multiple, simultaneous temporal modulations cannot be predicted from the neural responses to single modulations. Here we show the cortical neural representation of an auditory stimulus simultaneously frequency modulated (FM) at a high rate, fFM ? 40 Hz, and amplitude modulation (AM) at a slow rate, fAM
International Nuclear Information System (INIS)
The sensitivity of the standard 12-lead ECG for detecting myocardial ischemia is low perhaps because in the printed ECG only three to five complexes are examined, only absolute amplitude (voltage) criteria are used, and amplitude changes are sought only in the ST segment and T wave regions. A computerized method is proposed for evaluating the significance of ECG amplitude changes detected in one state compared with another (e.g. rest and stress). Amplitude changes were considered significant if they were consistently greater than the 'ECG variability contour' (EVC), which is a graphic measure introduced in this study, calculated from the reference ECG signal. Rest and stress simulation ECG (SECG) were constructed. Mean rest SECG complex was subtracted from rest and stress SECG complexes to result in rest and stress residue matrices, respectively. The percentage of the normalized cumulative sum (NCS) of the residues during stress (and rest) lying outside the EVC served as a measure for evaluating ECG changes associated with stress (and rest). With this method, amplitude changes of magnitude similar to that of the noise, which were difficult to detect visually, were easily detected and accurately allocated to the component of the ECG complex where they occurred. The proposed method may be useful in cases where amplitude changes are too subtle and thus overlooked or not detected by the standard examination of three to five complexes or underestimated due to unmet clinical (voltage) criteria, or occur in ECG components that are not regularly examined
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.
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.
Modulation transfer spectroscopy in atomic rubidium
McCarron, D.J.; King, S.A.; Cornish, S.L.
2008-01-01
We report modulation transfer spectroscopy on the D2 transitions in 85Rb and 87Rb using a simple home-built electro-optic modulator (EOM). We show that both the gradient and amplitude of modulation transfer spectroscopy signals, for the 87Rb F = 2 ? F' = 3 and the 85Rb F = 3 ? F' = 4 transitions, can be significantly enhanced by expanding the beams, improving the signals for laser frequency stabilization. The signal gradient for these transitions is increased by a factor of 3 and the peak to ...
Shkredov, Ilya D.
2013-01-01
We describe all sets $A \\subseteq \\F_p$ which represent the quadratic residues $R \\subseteq \\F_p$ as $R=A+A$ and $R=A\\hat{+} A$. Also, we consider the case of an approximate equality $R \\approx A+A$ and $R \\approx A\\hat{+} A$ and prove that $A$ has a structure in the situation.
Color-Kinematics Duality for QCD Amplitudes
Johansson, Henrik
2015-01-01
We show that color-kinematics duality is present in tree-level amplitudes of quantum chromodynamics with massive flavored quarks. Starting with the color structure of QCD, we work out a new color decomposition for n-point tree amplitudes in a reduced basis of primitive amplitudes. These primitives, with k quark-antiquark pairs and (n-2k) gluons, are taken in the (n-2)!/k! Melia basis, and are independent under the color-algebra Kleiss-Kuijf relations. This generalizes the color decomposition of Del Duca, Dixon, and Maltoni to an arbitrary number of quarks. The color coefficients in the new decomposition are given by compact expressions valid for arbitrary gauge group and representation. Considering the kinematic structure, we show through explicit calculations that color-kinematics duality holds for amplitudes with general configurations of gluons and massive quarks. The new (massive) amplitude relations that follow from the duality can be mapped to a well-defined subset of the familiar BCJ relations for gluo...
Characterization and reduction of the amplitude-to-phase conversion effects in telemetry
Guillory, J.; García-Márquez, J.; Alexandre, C.; Truong, D.; Wallerand, J.-P.
2015-08-01
We are developing a telemeter based on the measurement of the phase accumulated by an RF sine wave during its propagation in air. This wave is carried by a laser beam by an intensity modulation. The main limitation of this technique lies in amplitude-to-phase conversion occurring in the detection of this modulation. Therefore, we characterize this phenomenon for a given telemetric system and discuss how to reduce its effects on the resolution and the accuracy of the distance measurement. Finally, a solution is implemented and tested outdoors in real conditions of use.
International Nuclear Information System (INIS)
The results of the experiments wherein the distribution of the high-frequency whistling wave in the magnetized plasma duct was studied in the presence of the intensive low-frequency wave, also related to the whistling frequency range, are presented. The amplitude-frequency modulation of the high-frequency whistling wave captured in the duct is identified. The signal deep amplitude modulation which may lead its fragmentation into the separate wave packets is observed. It is shown that by increase in the wave distribution route there takes place widening of its frequency spectrum and the signal spectrum shift primarily to the red side is observed. The high-frequency wave transformation is connected with the nonstationary perturbation of the whistling wave low-frequency field (the relative magnetic field perturbation is ?B/B ? 5·10-2)
Multipole modes in deformed nuclei within the finite amplitude method
Kortelainen, M.; Hinohara, N.; Nazarewicz, W.
2015-11-01
Background: To access selected excited states of nuclei, within the framework of nuclear density functional theory, the quasiparticle random phase approximation (QRPA) is commonly used. Purpose: We present a computationally efficient, fully self-consistent framework to compute the QRPA transition strength function of an arbitrary multipole operator in axially deformed superfluid nuclei. Methods: The method is based on the finite amplitude method (FAM) QRPA, allowing fast iterative solution of QRPA equations. A numerical implementation of the FAM-QRPA solver module has been carried out for deformed nuclei. Results: The practical feasibility of the deformed FAM module has been demonstrated. In particular, we calculate the quadrupole and octupole strengths in a heavy deformed nucleus 240Pu, without any truncations in the quasiparticle space. To demonstrate the capability to calculate individual QRPA modes, we also compute low-lying negative-parity collective states in 154Sm. Conclusions: The new FAM implementation enables calculations of the QRPA strength function throughout the nuclear landscape. This will facilitate global surveys of multipole modes and ? decays and will open new avenues for constraining the nuclear energy density functional.
Residual stresses in material processing
Energy Technology Data Exchange (ETDEWEB)
Kozaczek, K.J.; Watkins, T.R.; Hubbard, C.R.; Wang, Xun-Li; Spooner, S.
1994-09-01
Material manufacturing processes often introduce residual stresses into the product. The residual stresses affect the properties of the material and often are detrimental. Therefore, the distribution and magnitude of residual stresses in the final product are usually an important factor in manufacturing process optimization or component life prediction. The present paper briefly discusses the causes of residual stresses. It then adresses the direct, nondestructive methods of residual stress measurement by X-ray and neutron diffraction. Examples are presented to demonstrate the importance of residual stress measurement in machining and joining operations.
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
Duality and effective amplitudes in quantum chromodynamics
International Nuclear Information System (INIS)
This work is an attempt to relate the partonic and hadronic phases of strong interactions by means of a model of effective string amplitudes which take into account color coherence without the need to restrict the phase-space. The basic idea of this approach is to construct, from open superstrings, string amplitudes which give, at the zero slope limit, QCD amplitudes. The running parameters (coupling and slope) of the model are constrained by perturbative QCD and by the consistency of string quantization. When the running slope becomes equal to the hadronic one, the model can be used in the hadronic sector. This approach could provide some hints about the effective string theory of QCD, and a better understanding of the parton-hadron duality
Perturbative type II amplitudes for BPS interactions
Basu, Anirban
2015-01-01
We consider the perturbative contributions to the R^4, D^4 R^4 and D^6 R^4 interactions in toroidally compactified type II string theory. These BPS interactions do not receive perturbative contributions beyond genus three. We derive Poisson equations satisfied by these moduli dependent string amplitudes. These T--duality invariant equations have eigenvalues that are completely determined by the structure of the integrands of the multi--loop amplitudes. The source terms are given by boundary terms of the moduli space of Riemann surfaces corresponding to both separating and non--separating nodes. These are determined directly from the string amplitudes, as well as from the logarithmic divergences of maximal supergravity. We explicitly solve these Poisson equations in nine and eight dimensions.
A Modified Modulation Recognition Method against Doppler Effects
Yaqin Zhao; Song Chen; Hang Yu; Zhenguo Shi
2011-01-01
In this study, we present a modified modulation recognition method- the way to seek the slope (TW-STS), based on decision theory, which can classify 7 kinds of basic digital modulation signals well under the influence of Doppler Effect. The proposed scheme is obtained by analyzing the influence to instantaneous amplitude, instantaneous phase and instantaneous frequency caused by Doppler Effect and modifying the original modulation recognition model. It can retrain the influence well and then ...
Herrmann, Björn; Henry, Molly J; Haegens, Saskia; Obleser, Jonas
2016-01-01
Alignment of neural oscillations with temporally regular input allows listeners to generate temporal expectations. However, it remains unclear how behavior is governed in the context of temporal variability: What role do temporal expectations play, and how do they interact with the strength of neural oscillatory activity? Here, human participants detected near-threshold targets in temporally variable acoustic sequences. Temporal expectation strength was estimated using an oscillator model and pre-target neural amplitudes in auditory cortex were extracted from magnetoencephalography signals. Temporal expectations modulated target-detection performance, however, only when neural delta-band amplitudes were large. Thus, slow neural oscillations act to gate influences of temporal expectation on perception. Furthermore, slow amplitude fluctuations governed linear and quadratic influences of auditory alpha-band activity on performance. By fusing a model of temporal expectation with neural oscillatory dynamics, the current findings show that human perception in temporally variable contexts relies on complex interactions between multiple neural frequency bands. PMID:26386347
Systems for amplitude and time measurement in deep-water experiment
International Nuclear Information System (INIS)
In deep-water experiments in Lake Baikal for registration of elementary particles, the measuring apparatus, which includes systems for measurement of the total amplitude of signals from two photomultipliers (PM) and their actuation times, is under water at a depth of 1 km and at a straight-line distance of about 4 km from the on-shore data acquisition and processing center; therefore, in addition to reliability of the electronic devices, it is necessary to ensure sufficient measurement accuracy and speed with low energy consumption. These conditions determine the component base for the amplitude- and time-measurement systems. The units of a deep-water optical module are described: a system for measurement of the total amplitude of signals from two photomultipliers whose linear range is within 100 photoelectrons; and a system for time measurement in the range of 5-250 nsec with 3-nsec accuracy
A high-bandwidth amplitude estimation technique for dynamic mode atomic force microscopy
Energy Technology Data Exchange (ETDEWEB)
Karvinen, K. S., E-mail: Kai.Karvinen@uon.edu.au; Moheimani, S. O. R., E-mail: Reza.Moheimani@newcastle.edu.au [School of Electrical Engineering and Computer Science, The University of Newcastle, Callaghan, NSW 2308 (Australia)
2014-02-15
While often overlooked, one of the prerequisites for high-speed amplitude modulation atomic force microscopy is a high-bandwidth amplitude estimation technique. Conventional techniques, such as RMS to DC conversion and the lock-in amplifier, have proven useful, but offer limited measurement bandwidth and are not suitable for high-speed imaging. Several groups have developed techniques, but many of these are either difficult to implement or lack robustness. In this contribution, we briefly outline existing amplitude estimation methods and propose a new high-bandwidth estimation technique, inspired by techniques employed in microwave and RF circuit design, which utilizes phase cancellation to significantly improve the performance of the lock-in amplifier. We conclude with the design and implementation of a custom circuit to experimentally demonstrate the improvements and discuss its application in high-speed and multifrequency atomic force microscopy.
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.)
Module amenability for Banach modules
D Ebrahimi Bagha; Amini, M.
2011-01-01
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 pointwise multiplication.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 ...
Singularity Structure of Maximally Supersymmetric Scattering Amplitudes
DEFF Research Database (Denmark)
Arkani-Hamed, Nima; Bourjaily, Jacob L.; Cachazo, Freddy; Trnka, Jaroslav
2014-01-01
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) s...
Time-varying interaction leads to amplitude death in coupled nonlinear oscillators
Indian Academy of Sciences (India)
Awadhesh Prasad
2013-09-01
A new form of time-varying interaction in coupled oscillators is introduced. In this interaction, each individual oscillator has always time-independent self-feedback while its interaction with other oscillators are modulated with time-varying function. This interaction gives rise to a phenomenon called amplitude death even in diffusively coupled identical oscillators. The nonlinear variation of the locus of bifurcation point is shown. Results are illustrated with Landau–Stuart (LS) and Rössler oscillators.
Phase and Amplitude Responses of Narrow-Band Optical Filter Measured by Microwave Network Analyzer
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 an...
High-frequency instabilities of small-amplitude solutions of Hamiltonian PDEs
Deconinck, Bernard; Trichtchenko, Olga
2015-01-01
Generalizing ideas of MacKay, and MacKay and Saffman, a necessary condition for the presence of high-frequency ( i.e., not modulational) instabilities of small-amplitude periodic solutions of Hamiltonian partial differential equations is presented, entirely in terms of the Hamiltonian of the linearized problem. With the exception of a Krein signature calculation, the theory is completely phrased in terms of the dispersion relation of the linear problem. The general theory ch...
Lobanov, Valery E; Gorodetsky, Michael L
2015-01-01
We demonstrate that flat-topped dissipative solitonic pulses, platicons, and corresponding frequency combs can be excited in optical microresonators with normal group velocity dispersion using either amplitude modulation of the pump or bichromatic pump. Soft excitation may occur in particular frequency range if modulation depth is large enough and modulation frequency is close to the free spectral range of the microresonator.
Residual subsidence analysis after the end of coal mine work. Example from Lorraine Colliery, France
International Nuclear Information System (INIS)
This paper describes the residual movements associated with the deep coal mines. The studied case relates to works located into Lorraine coal basin. The paper is divided into two sections. The first one describes subsidence phenomena, especially the residual phase in terms of amplitude, duration and localization. The second one focus on Morsbach case: the total and residual subsidence measurements will be analyzed and compared to the state of the art as well as the currant knowledge. The results of the analysis show that the duration of residual movements does not exceed 24 months and their amplitude is about 5% of total subsidence. We analyze also the declarations of the mining damage during and after the mining period. Damages occur, after this period are probably due to late observations. (authors)
Agricultural pesticide residues
International Nuclear Information System (INIS)
Tracer techniques used in the elucidation of the pathways and fate of pesticides in agriculture are reviewed. Such studies include investigating the uptake of labelled pesticides into plants in lysimeter and micro-ecosystem experiments, the translocations of pesticides in the soil, the degradation of pesticides in the soil, the biological availability of soil-applied substances and the bound pesticide residues in the soil. The use of macro- and microautoradiography and double and triple labelling is also described. (U.K.)
Ballauff, M.; Brader, J. M.; Egelhaaf, S. U.; Fuchs, M.; Horbach, J.; N. Koumakis; Krüger, M.; Laurati, M.; Mutch, K J; Petekidis, G.; Siebenbürger, M.; Voigtmann, Th.; Zausch, J.
2013-01-01
The history dependence of the glasses formed from flow-melted steady states by a sudden cessation of the shear rate $\\dot\\gamma$ is studied in colloidal suspensions, by molecular dynamics simulations, and mode-coupling theory. In an ideal glass, stresses relax only partially, leaving behind a finite persistent residual stress. For intermediate times, relaxation curves scale as a function of $\\dot\\gamma t$, even though no flow is present. The macroscopic stress evolution is c...
Designing with residual materials:
Walhout, W.; Wever, R; Blom, E.; Addink-Dölle, L.; Tempelman, E.
2013-01-01
Many entrepreneurial businesses have attempted to create value based on the residual material streams of third parties. Based on ‘waste’ materials they designed products, around which they built their company. Such activities have the potential to yield sustainable products. Many of such companies remain in the more artistic domain, with relatively labor-intensive products, and small batch sizes. Moving beyond such small-scale activities would likely require a standardized innovation process....
Crack propagation under variable amplitude loading
Scientific Electronic Library Online (English)
Miloudi, Abdelkader; Zemri, Mokhtar; Benguediab, Mohamed; Mazari, Mohamed; Amrouche, Abdelwaheb.
2013-10-01
Full Text Available 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.
Higgs Amplitudes From Twistor Inspired Methods
International Nuclear Information System (INIS)
We illustrate the use of new on-shell methods, 4-dimensional unitarity cuts combined with on-shell recursions relations by computing the A(1)4 (1-, 2-, 3+, 4+) amplitude in the large top mass limit where the Higgs boson couples to gluons through an effective interaction. (author)
Higgs Amplitudes From Twistor Inspired Methods
Badger, S D; Risager, Kasper
2007-01-01
We illustrate the use of new on-shell methods, 4-dimensional unitarity cuts combined with on-shell recursions relations, by computing the A_4^{(1)}(phi,1^-,2^-,3^+,4^+) amplitude in the large top mass limit where the Higgs boson couples to gluons through an effective interaction.
Particle Distribution Modification by Low Amplitude Modes
Energy Technology Data Exchange (ETDEWEB)
White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.
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.
Generalised Unitarity for Dimensionally Regulated Amplitudes
Bobadilla, W J Torres; Mastrolia, P; Mirabella, E
2015-01-01
We present a novel set of Feynman rules and generalised unitarity cut-conditions for computing one-loop amplitudes via d-dimensional integrand reduction algorithm. Our algorithm is suited for analytic as well as numerical result, because all ingredients turn out to have a four-dimensional representation. We will apply this formalism to NLO QCD corrections.
Amplitude ratios for complete moment tensor retrieval.
Czech Academy of Sciences Publication Activity Database
Jechumtálová, Zuzana; Šílený, Jan
2005-01-01
Ro?. 32, ?. 22 (2005), L22303/1-4. ISSN 0094-8276 R&D Projects: GA AV ?R KJB300120504; GA AV ?R IAA300120502 Institutional research plan: CEZ:AV0Z30120515 Keywords : seismic moment tensor * amplitude ratios * non-shear source component Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.491, year: 2005
Directory of Open Access Journals (Sweden)
Nevijo Zdolec
2006-07-01
Full Text Available Various chemical agents are used during the whole production chain of milk and dairy products. Production of feedingstuffs is accompanied with pesticide usage, which may remain in environment, thus are transported through feeding into animals, animal products and finally in human organism. Preparation procedure and storage conditions of feed also influence on milk safety in the sense of mycotoxins entering into the food chain. Chemical agents are, on daily basis, used on dairy farms either as detergents or disinfections. The residuals of cleaning agents might remain in milk if the cleaning agents and its dosage are not performed adequately. Besides already mentioned agents, a great influence in milk production can bee seen through veterinary drugs usage, particularly antibacterial drugs (mastitis. Proper application of drugs and by following legal recommendation, a by-reactions can be avoided such as allergic reaction in humans, development of resisting bacteria or even undesirable influence on starter cultures in dairy products manufacture. The maximum residue limits, monitoring plan as well as sampling procedures are set up within the harmonization of Croatian and European legislation, in order to provide official control of residues in foodstuffs of animal origin.
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
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 program is needed to find the right result, what gives a cleaner result. (author)
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.
Control of catalytic efficiency by a coevolving network of catalytic and noncatalytic residues.
McMurrough, Thomas A; Dickson, Russell J; Thibert, Stephanie M F; Gloor, Gregory B; Edgell, David R
2014-06-10
The active sites of enzymes consist of residues necessary for catalysis and structurally important noncatalytic residues that together maintain the architecture and function of the active site. Examples of evolutionary interactions between catalytic and noncatalytic residues have been difficult to define and experimentally validate due to a general intolerance of these residues to substitution. Here, using computational methods to predict coevolving residues, we identify a network of positions consisting of two catalytic metal-binding residues and two adjacent noncatalytic residues in LAGLIDADG homing endonucleases (LHEs). Distinct combinations of the four residues in the network map to distinct LHE subfamilies, with a striking distribution of the metal-binding Asp (D) and Glu (E) residues. Mutation of these four positions in three LHEs--I-LtrI, I-OnuI, and I-HjeMI--indicate that the combinations of residues tolerated are specific to each enzyme. Kinetic analyses under single-turnover conditions revealed that I-LtrI activity could be modulated over an ?100-fold range by mutation of residues in the coevolving network. I-LtrI catalytic site variants with low activity could be rescued by compensatory mutations at adjacent noncatalytic sites that restore an optimal coevolving network and vice versa. Our results demonstrate that LHE activity is constrained by an evolutionary barrier of residues with strong context-dependent effects. Creation of optimal coevolving active-site networks is therefore an important consideration in engineering of LHEs and other enzymes. PMID:24912189
PRINCIPLE OF SKEW QUADRUPOLE MODULATION TO MEASURE BETATRON COUPLING.
Energy Technology Data Exchange (ETDEWEB)
LUO.Y.PILAT,F.ROSER,T.ET AL.
2004-07-05
The measurement of the residual betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been developed and tested at the Relativistic Heavy Ion Collider (RHIC) as a very promising method for the linear decoupling on the ramp. By modulating the strengths of different skew quadrupole families the two eigentunes are precisely measured with the phase lock loop system. The projections of the residual coupling coefficient onto the skew quadrupole coupling modulation directions are determined. The residual linear coupling could be corrected according to the measurement. An analytical solution for skew quadrupole modulation based on Hamiltonian perturbation approximation is given, and simulation code using smooth accelerator model is also developed. Some issues concerning the practical applications of this technique are discussed.
Recursion Relations for Gauge Theory Amplitudes with Massive Particles
Badger, S D; Khoze, V V; Svrcek, P
2005-01-01
We derive general tree-level recursion relations for amplitudes which include massive propagating particles. As an illustration, we apply these recursion relations to scattering amplitudes of gluons coupled to massive scalars. We provide new results for all amplitudes with a pair of scalars and n < 5 gluons. These amplitudes can be used as building blocks in the computation of one-loop 6-gluon amplitudes using unitarity based methods.
Recursion relations for gauge theory amplitudes with massive particles
International Nuclear Information System (INIS)
We derive general tree-level recursion relations for amplitudes which include massive propagating particles. As an illustration, we apply these recursion relations to scattering amplitudes of gluons coupled to massive scalars. We provide new results for all amplitudes with a pair of scalars and n ? 4 gluons. These amplitudes can be used as building blocks in the computation of one-loop 6-gluon amplitudes using unitarity based methods
One-loop triple collinear splitting amplitudes in QCD
Badger, Simon; Peraro, Tiziano
2015-01-01
We study the factorisation properties of one-loop scattering amplitudes in the triple collinear limit and extract the universal splitting amplitudes for processes initiated by a gluon. The splitting amplitudes are derived from the analytic Higgs plus four partons amplitudes. We present compact results for primitive helicity splitting amplitudes making use of super-symmetric decompositions. The universality of the collinear factorisation is checked numerically against the full colour six parton squared matrix elements.
Multigluon amplitudes in the high-energy limit
Del Duca, V
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.
New chopper modulators using differential voltage current conveyor
Directory of Open Access Journals (Sweden)
M. Kumngern
2011-06-01
Full Text Available This paper presents new chopper modulators which can enable to assign three modulators in one circuit. Full amplitude modulators as Cowan and Ring modulators are kinds of the amplitude modulators as well. The proposed circuit is implemented from the differential voltage current conveyor, four-MOS transistors switch and two-MOS transistors inverter. The advantage of this proposed circuit is high input and low output impedance and is able to be connected with any load without buffer and the number of transistors is quite less which is suitable for integrated circuits. The technique is to control the switch by using the square pulse which is obtained from a direct signal generator. All simulation results are based on the PSPICE program simulator which confirms the performance of the proposed circuit and technique.
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.
Module amenability for Banach modules
Scientific Electronic Library Online (English)
D, Ebrahimi Bagha; M, Amini.
2011-06-01
Full Text Available 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.
Chikhladze, Dimitri
2010-01-01
There are various generalizations of bialgebras to their ''many object'' versions, such as quantum categories, bialgebroids and weak bialgebras. These can also be thought of as quantum analogues of small categories. In this paper we study modules over these structures, which are quantum analogues of profunctors (also called distributors) between small categories.
Complete N-Point Superstring Disk Amplitude II. Amplitude and Hypergeometric Function Structure
Mafra, Carlos R; Stieberger, Stephan
2011-01-01
Using the pure spinor formalism in part I [1] we compute the complete tree-level amplitude of N massless open strings and find a striking simple and compact form in terms of minimal building blocks: the full N-point amplitude is expressed by a sum over (N-3)! Yang-Mills partial subamplitudes each multiplying a multiple Gaussian hypergeometric function. While the former capture the space-time kinematics of the amplitude the latter encode the string effects. This result disguises a lot of structure linking aspects of gauge amplitudes as color and kinematics with properties of generalized Euler integrals. In this part II the structure of the multiple hypergeometric functions is analyzed in detail: their relations to monodromy equations, their minimal basis structure, and methods to determine their poles and transcendentality properties are proposed. Finally, a Groebner basis analysis provides independent sets of rational functions in the Euler integrals.
General covariant transition amplitudes in quantum cosmology
Vidotto, Francesca
2011-01-01
The path-integral approach to cosmology consists in the computation of transition amplitudes between states of the quantum geometry of the universe. In the past, the concrete computation of these transitions amplitudes has been performed in a perturbative regime, breaking the full general covariance of the theory. Here I present how it is possible to define a general covariant path integral in quantum cosmology, by relying on the most recent results of the canonical and covariant formulations of Loop Quantum Gravity. I present two strategies that have been implemented. The first starts from the full Spinfoam theory, i.e. the path-integral framework for Loop Quantum Gravity, and defines a cosmological system. This is not obtained from symmetry reduced variables that are successively quantized, but directly considering the approximations that are characteristic of the full theory. The Spinfoam Cosmology obtained in this way includes quantum fluctuations beyond standard perturbation theory. The second strategy e...
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)
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.
Constructing QCD one-loop amplitudes
International Nuclear Information System (INIS)
In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 (varepsilon). The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally other new methods have also proved fruitful for calculating rational terms [8]. Such developments have again refocused attention on the optimization of the derivation of the cut-constructable pieces of the amplitude. Deriving cut-constructible terms for any one-loop amplitude reduces to the computation of coefficients of a set of scalar bubble, scalar triangle and scalar box integral functions. Box coefficients may be found with very little work, directly from the quadruple cut of the relevant box function [9]. A unique box coefficient contributes to each distinct quadruple cut. Unfortunately triangle and bubble coefficients cannot be derived in quite so direct a manner. Multiple scalar integral coefficients appear inside a two-particle cut or triple cut. It is therefore necessary to disentangle the relevant bubble or triangle coefficients from any other coefficients sharing the same cut [1, 4, 10, 11]. The large number of NLO processes of interest for the LHC suggests that a completely automated computational procedure is highly desired. To this end we discuss, in this proceeding, a recently proposed method [12, 13] for the direct, efficient and systematic extraction of bubble and triangle coefficients which is well suited to automation
Limit on the pion distribution amplitude
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.
Limit on the pion distribution amplitude
Luna, E. G. S.; Natale, A. A.
2015-01-01
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}? ? {{? *}}}({{Q}2}). The resulting upper limit on the pion transition form factor is compared with existing data published by CLEO, BaBar and Belle Collaborations.
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.)
Wu, Liang; Cheng, Shubo; Tao, Shaohua
2015-10-01
An iterative beam shaping algorithm is proposed to simultaneously shape the amplitude and phase of an optical beam. The proposed algorithm consists of one input plane and two completely overlapped output planes which refer to the output plane in real space. The two output planes are imposed with both amplitude and phase constraints, and the constrained areas in the two output planes are complementary. As a result, both the amplitude and phase in the entire output plane are controllable and arbitrary target complex amplitudes can be achieved with the proposed algorithm. The computing result of the proposed algorithm is a phase-only distribution which can be conveniently realized with a spatial light modulator or a fabricated diffractive optical element. Both simulations and experiments have verified the high performance of the proposed algorithm.
Wu, Liang; Cheng, Shubo; Tao, Shaohua
2015-01-01
An iterative beam shaping algorithm is proposed to simultaneously shape the amplitude and phase of an optical beam. The proposed algorithm consists of one input plane and two completely overlapped output planes which refer to the output plane in real space. The two output planes are imposed with both amplitude and phase constraints, and the constrained areas in the two output planes are complementary. As a result, both the amplitude and phase in the entire output plane are controllable and arbitrary target complex amplitudes can be achieved with the proposed algorithm. The computing result of the proposed algorithm is a phase-only distribution which can be conveniently realized with a spatial light modulator or a fabricated diffractive optical element. Both simulations and experiments have verified the high performance of the proposed algorithm. PMID:26486183
Infrared Observations of Large Amplitude Pulsating Stars
Whitelock, Patricia A
1997-01-01
Our understanding of large amplitude pulsating stars and their status in stellar evolution is briefly reviewed. The paper then describes the near-infrared light curves of various asymptotic giant branch stars, concentrating on possible evidence for changing mass-loss rates. The stars discussed include oxygen- and carbon-rich Miras, OH/IR stars, thick-shelled carbon stars and symbiotic Miras. Finally a newly discovered Mira variable in the Sagittarius Dwarf Galaxy is described.
Annulus amplitude of FZZT branes revisited
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.
Understanding the amplitudes of noise correlation measurements
Tsai, Victor C.
2011-01-01
Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.
Yangian symmetric correlators, R operators and amplitudes
Kirschner, R.
2014-11-01
Yangian symmetric correlators can be constructed by the action of Yang-Baxter R operators on trivial basic correlators. The example of a four-point correlator is given in two representations and the construction of the completely connected N point correlator is described. The helicity representation is dicussed and the relation of the four-point correlator to tree-level scattering amplitudes is shown.
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.
Amplitude death in coupled chaotic oscillators
Prasad, Awadhesh
2005-01-01
Amplitude death can occur in chaotic dynamical systems with time-delay coupling, similar to the case of coupled limit cycles. The coupling leads to stabilization of fixed points of the subsystems. This phenomenon is quite general, and occurs for identical as well as nonidentical coupled chaotic systems. Using the Lorenz and R\\"ossler chaotic oscillators to construct representative systems, various possible transitions from chaotic dynamics to fixed points are discussed.
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.
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
Continuous phase and amplitude holographic elements
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.
Connecting physical resonant amplitudes and lattice QCD
Bolton, Daniel R; Wilson, David J
2015-01-01
We present a determination of the isovector, $P$-wave $\\pi\\pi$ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using $m_\\pi =236$ MeV. The finite volume spectra are described using extensions of L\\"uscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at $m_\\pi= 140$ MeV. The scattering phase shift is found to be in good agreement with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a $\\rho$-resonance pole at $E_\\rho= \\left[755(2)(1)(^{20}_{02})-\\frac{i}{2}\\,129(3)(1)(^{7}_{1})\\right]~{\\rm MeV}$. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.
Scattering amplitudes in super-renormalizable gravity
Donà, Pietro; Modesto, Leonardo; Rachwal, Leslaw; Zhu, Yiwei
2015-01-01
We explicitly compute the tree-level on-shell four-graviton amplitudes in four, five and six dimensions for local and weakly nonlocal gravitational theories that are quadratic in both, the Ricci and scalar curvature with form factors of the d'Alembertian operator inserted between. More specifically we are interested in renormalizable, super-renormalizable or finite theories. The scattering amplitudes for these theories turn out to be the same as the ones of Einstein gravity regardless of the explicit form of the form factors. As a special case the four-graviton scattering amplitudes in Weyl conformal gravity are identically zero. Using a field redefinition, we prove that the outcome is correct for any number of external gravitons (on-shell $n-$point functions) and in any dimension for a large class of theories. However, when an operator quadratic in the Riemann tensor is added in any dimension (with the exception of the Gauss-Bonnet term in four dimensions) the result is completely altered, and the scattering...
Quantifying Residual Stresses by Means of Thermoelastic Stress Analysis
Gyekenyesi, Andrew L.; Baaklini, George Y.
2001-01-01
This study focused on the application of the Thermoelastic Stress Analysis (TSA) technique as a tool for assessing the residual stress state of structures. TSA is based on the fact that materials experience small temperature changes when compressed or expanded. When a structure is cyclically loaded, a surface temperature profile results which correlates to the surface stresses. The cyclic surface temperature is measured with an infrared camera. Traditionally, the amplitude of a TSA signal was theoretically defined to be linearly dependent on the cyclic stress amplitude. Recent studies have established that the temperature response is also dependent on the cyclic mean stress (i.e., the static stress state of the structure). In a previous study by the authors, it was shown that mean stresses significantly influenced the TSA results for titanium- and nickel-based alloys. This study continued the effort of accurate direct measurements of the mean stress effect by implementing various experimental modifications. In addition, a more in-depth analysis was conducted which involved analyzing the second harmonic of the temperature response. By obtaining the amplitudes of the first and second harmonics, the stress amplitude and the mean stress at a given point on a structure subjected to a cyclic load can be simultaneously obtained. The experimental results showed good agreement with the theoretical predictions for both the first and second harmonics of the temperature response. As a result, confidence was achieved concerning the ability to simultaneously obtain values for the static stress state as well as the cyclic stress amplitude of structures subjected to cyclic loads using the TSA technique. With continued research, it is now feasible to establish a protocol that would enable the monitoring of residual stresses in structures utilizing TSA.
Optical modulation characteristics and applications of liquid crystal televisions
Kirsch, James C.
1992-05-01
One of the most critical components in optical information processing systems is the spatial light modulator (SLM), which typically limits both system speed and space-bandwidth. Cost has been a major drawback for commercial applications. This report covers the improving SPL, the liquid crystal television (LCTV). Two LCTV's were selected for test measurements, the SEIKO LVD202 pocket color LCTV and the Epson Crystal Image video projector. Phase and amplitude modulation were checked with the LVD202 achieving a visibility of 0.94 in an amplitude modulating mode (AMM) and modulated in excess of 360 degrees of phase. The Epson LCTV achieved a visibility of 0.96 in AMM and modulated 336 degrees of phase. Two phase-mostly joint transform optical correlator constructed with two Seiko LCTV's performed as well as a similar amplitude modulating (AM) JTC, with a much higher light efficiency. The Epson LCTV served as a phase-only input to a Vandderlugt optical correlator with results similar to traditional amplitude input correlator. This correlator also proved to be more light efficient than AM architecture. The report discusses experiment results and possible future research directions.
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)
International Nuclear Information System (INIS)
This thesis covers two main topics: the tensorial structure of quantum field theory correlators in general spacetime dimensions and a method for computing string theory scattering amplitudes directly in target space. In the first part tensor structures in generic bosonic CFT correlators and scattering amplitudes are studied. To this end arbitrary irreducible tensor representations of SO(d) (traceless mixed-symmetry tensors) are encoded in group invariant polynomials, by contracting with sets of commuting and anticommuting polarization vectors which implement the index symmetries of the tensors. The tensor structures appearing in CFTd correlators can then be inferred by studying these polynomials in a d + 2 dimensional embedding space. It is shown with an example how these correlators can be used to compute general conformal blocks describing the exchange of mixed-symmetry tensors in four-point functions, which are crucial for advancing the conformal bootstrap program to correlators of operators with spin. Bosonic string theory lends itself as an ideal example for applying the same methods to scattering amplitudes, due to its particle spectrum of arbitrary mixed-symmetry tensors. This allows in principle the definition of on-shell recursion relations for string theory amplitudes. A further chapter introduces a different target space definition of string scattering amplitudes. As in the case of on-shell recursion relations, the amplitudes are expressed in terms of their residues via BCFW shifts. The new idea here is that the residues are determined by use of the monodromy relations for open string theory, avoiding the infinite sums over the spectrum arising in on-shell recursion relations. Several checks of the method are presented, including a derivation of the Koba-Nielsen amplitude in the bosonic string. It is argued that this method provides a target space definition of the complete S-matrix of string theory at tree-level in a at background in terms of a small set of conditions, without relying on any worldsheet computation.
The resonant $\\pi^+\\gamma\\to\\pi^+\\pi^0$ amplitude from Quantum Chromodynamics
Briceno, Raul A; Edwards, Robert G; Shultz, Christian J; Thomas, Christopher E; Wilson, David J
2015-01-01
We present the first ab initio calculation of a radiative transition of a hadronic resonance within Quantum Chromodynamics (QCD). We compute the amplitude for $\\pi\\pi \\to \\pi\\gamma^\\star$, as a function of the energy of the $\\pi\\pi$ pair and the virtuality of the photon, in the kinematic regime where $\\pi\\pi$ couples strongly to the unstable $\\rho$ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to $m_\\pi \\approx 400$ MeV. We obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the $\\rho$ pole and identify from its residue the $\\rho \\to \\pi\\gamma^\\star$ form-factor.
Modulated envelope localized wavepackets associated with electrostatic plasma waves
Kourakis, I; Kourakis, Ioannis; Shukla, Padma Kant
2004-01-01
The nonlinear amplitude modulation of known electrostatic plasma modes is examined in a generic manner, by applying a collisionless fluid model. Both cold (zero-temperature) and warm fluid descriptions are discussed and the results are compared. The moderately nonlinear oscillation regime is investigated by applying a multiple scale technique. The calculation leads to a Nonlinear Schrodinger-type Equation (NLSE), which describes the evolution of the slowly varying wave amplitude in time and space. The NLSE admits localized envelope (solitary wave) solutions of bright- (pulses) or dark- (holes, voids) type, whose characteristics (maximum amplitude, width) depend on intrinsic plasma parameters. Effects like amplitude perturbation obliqueness, finite temperature and defect (dust) concetration are explicitly considered. The relevance with similar highly localized modulated wave structures observed during recent satellite missions is discussed.
Study of the modulation capabilities of parallel aligned liquid crystal on silicon displays
Márquez Ruiz, Andrés; Martínez Guardiola, Francisco Javier; Gallego Rico, Sergi; Ortuño Sánchez, Manuel; Francés Monllor, Jorge; Beléndez Vázquez, Augusto; Pascual Villalobos, Inmaculada
2013-01-01
Among the existent technologies of spatial light modulator devices, parallel aligned liquid crystal on silicon displays (PA-LCoS) have found wide acceptance. They are especially interesting since they provide phase-only modulation with no coupling of amplitude modulation. Optimal use of these devices requires proper calibration of their modulation capabilities in order to minimize some degradation effects found in the literature, such as flicker or anamorphic and frequency dependent modulatio...
Oblique Modulation of Ion-Acoustic Waves in a Warm Plasma
International Nuclear Information System (INIS)
The stability of oblique modulation of ion-acoustic waves in an unmagnetized warm plasma is studied. A nonlinear Schroedinger equation governing the slow modulation of the wave amplitude is derived. The effect of temperature on the oblique modulational instability of the ion-acoustic wave is investigated. It is found that the ion temperature significantly changes the domain of the modulational instability in the k-? plane
Field modulator microwave absorption in YBa2Cu3O7-X thin films
International Nuclear Information System (INIS)
The authors report investigations on the field modulated non resonant microwave absorption in the superconducting state of textured YBa2Cu3O7-x thin films. The temperature dependence of the modulated signal shows irregular structures below Tc which are shifted towards lower temperature with increasing the amplitude of the modulation field. The modulated signal shows, as a function of the applied field, a rather regular pattern of narrow lines. These results are ascribed to a distribution of weak intergrain Josephson links
Photonic Crystal Fano Laser: Terahertz Modulation and Ultrashort Pulse Generation
DEFF Research Database (Denmark)
MØrk, Jesper; Chen, Yaohui
2014-01-01
We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory.
Scannerless laser range imaging using loss modulation
Sandusky, John V. (Albuquerque, NM)
2011-08-09
A scannerless 3-D imaging apparatus is disclosed which utilizes an amplitude modulated cw light source to illuminate a field of view containing a target of interest. Backscattered light from the target is passed through one or more loss modulators which are modulated at the same frequency as the light source, but with a phase delay .delta. which can be fixed or variable. The backscattered light is demodulated by the loss modulator and detected with a CCD, CMOS or focal plane array (FPA) detector to construct a 3-D image of the target. The scannerless 3-D imaging apparatus, which can operate in the eye-safe wavelength region 1.4-1.7 .mu.m and which can be constructed as a flash LADAR, has applications for vehicle collision avoidance, autonomous rendezvous and docking, robotic vision, industrial inspection and measurement, 3-D cameras, and facial recognition.
Shinbori, A.; Koyama, Y.; Hayashi, H.; Nose, M.; Hori, T.; Otsuka, Y.; Tsuda, T.
2011-12-01
It has been well-known that geomagnetic solar quiet (Sq) daily variation is produced by global ionospheric currents flowing in the E-region from middle latitudes to the magnetic equator. These currents are generated by a dynamo process via interaction between the neutral wind and ionospheric plasma in a region of the thermosphere and ionosphere. From the Ohm's equation, the ionospheric currents strongly depend on the ionospheric conductivity, polarization electric field and neutral wind. Then, to investigate the Sq amplitude is essential for understanding the long-term variations in the ionospheric conductivity and neutral wind of the thermosphere and ionosphere. Elias et al. [2010] found that the Sq amplitude tends to increase by 5.4-9.9 % in the middle latitudes from 1961 to 2001. They mentioned that the long-term variation of ionospheric conductivity associated with geomagnetic secular variation mainly determines the Sq trend, but that the rest component is ionospheric conductivity enhancement associated with cooling effects in the thermosphere due to increasing the greenhouse gases. In this talk, we clarify the characteristics of the long-term variation in the Sq amplitude using the long-term observation data of geomagnetic field and neutral wind. These observation data have been provided by the IUGONET (Inter-university Upper atmosphere Global Observation NETwork) project. In the present analysis, we used the F10.7 flux as an indicator of the variation in the solar irradiance in the EUV and UV range, geomagnetic field data with time resolution of 1 hour. The definition of the Sq amplitude is the difference of the H-component between the maximum and minimum per day when the Kp index is less than 4. As a result, the Sq amplitude at all the stations strongly depends on 11-year solar activity, and tends to enhance more during the high activities (19- and 22- solar cycles) than during the low activity (20-solar cycle). The Fourier spectra of the F10.7 flux and Sq amplitude at Guam (13.59N, 144.87E) showed that the common peaks appear at the periods of 5.5, 7,5 and 10.5 years with the coherence of more than 0.9 while the spectrum peaks around 0.5 and 1.0 year appear only in the Sq amplitude. The former peak of the Sq amplitude is due to the solar activity while the latter is a cause of the upper atmosphere variation. In order to minimize the solar activity dependence of the Sq amplitude, we calculated the residual Sq amplitude using a second degree polynomial curve between the F10.7 and Sq amplitude during 1957-2010, and examined the residual Sq field defined as the deviation from the fitting curve. The residual Sq amplitude showed a clear tendency to increase and decrease during the periods of 1957-1992 and 1993-2010, respectively. It should be noted that the residual Sq amplitude around 2010 is almost the same level as that around 1970. In order to verify qualitatively the above signatures, we need to investigate the long-term variation in the ionospheric conductivities calculated with the IRI-2007 and MSIS-00 models.
ABJM Amplitudes in U-gauge and a Soft Theorem
Chin, Seungbeom; Yun, Youngbin
2015-01-01
We report progress in computing and analyzing all tree amplitudes in ABJM theory. Inspired by the isomorphism between the orthogonal Grassmannian and the pure spinor geometries, we adopt a new gauge, called u-gauge, for evaluating the orthogonal Grassmannian integral for ABJM amplitudes. We carry out the integral explicitly for the 8-point amplitude and obtain the complete supersymmetric amplitude. The physical and spurious poles arise from the integral as expected from on-shell diagrams. We also derive a double scalar soft theorem of ABJM amplitudes and verify it for known amplitudes.
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.
Landfilling of waste incineration residues
DEFF Research Database (Denmark)
Christensen, Thomas Højlund; Astrup, Thomas; Cai, Zuansi; Chen, D.
2002-01-01
Residues from waste incineration are bottom ashes and air-pollution-control (APC) residues including fly ashes. The leaching of heavy metals and salts from the ashes is substantial and a wide spectrum of leaching tests and corresponding criteria have been introduced to regulate the landfilling of the ashes. Leaching test, however, must be selected carefully to provide information relevant for the actual disposal scenario and for evaluating the benefits of pre-treating the residues prior to landf...
Relaxation of residual stresses induced by laser shock processing
Scientific Electronic Library Online (English)
C., Rubio-González; A., Garnica-Guzmán; G., Gómez-Rosas.
2009-08-01
Full Text Available El Proceso de Impacto con Laser (LSP) es una técnica novedosa para el tratamiento de superficies que induce campos de esfuerzos residuales de compresión. Este trabajo examina los efectos de cargas cíclicas y el efecto de la temperatura en la estabilidad de los campos de esfuerzos inducidos por la té [...] cnica LSP en muestras de aluminio 6061-T6. Se reporta la relajación de esfuerzos residuales debidos a las cargas cíclicas para diferentes amplitudes de esfuerzos y diferentes temperaturas. Debido a los efectos de la fluencia cíclica, los esfuerzos residuales decrecen linealmente con el logaritmo del número de ciclos, N. Abstract in english The Laser shock processing (LSP) is a new surface treatment technique that induces a compressive residual stress field. This work examines the effect of cyclic loading and temperature on the stability of the stress field induced by LSP on 6061-T6 aluminum samples. Residual stress relaxation due to c [...] yclic loading is reported for different stress amplitudes and temperatures. Due to the cyclic creep effect, the residual stress decreases linearly with the logarithm of the number of cycles, N.
Performance Evaluation of Adaptive Modulation System over Mobile Satellite Channels
Jinxiu Chen; Chao Dong; Youzheng Wang
2013-01-01
The performance of an adaptive five-mode M-ary quadrature amplitude modulation (QAM) system under constant power constraint over time-varying land mobile satellite channel is evaluated in this paper. The mathematically-tractable closed-form expressions of performance for outage probability, bit error rate (BER) and average spectral efficiency are deduced by a simple Rician channel model in which the amplitude of the line-of-sight path is represented by the Nakagami distribution. Two adaptive ...
Microwave emission and crop residues
International Nuclear Information System (INIS)
A series of controlled experiments were conducted to determine the significance of crop residues or stubble in estimating the emission of the underlying soil. Observations using truckmounted L and C band passive microwave radiometers showed that for dry wheat and soybeans the dry residue caused negligible attenuation of the background emission. Green residues, with water contents typical of standing crops, did have a significant effect on the background emission. Results for these green residues also indicated that extremes in plant structure, as created using parallel and perpendicular stalk orientations, can cause very large differences in the degree of attenuation
Immobilization of acid digestion residue
International Nuclear Information System (INIS)
Acid digestion treatment of nuclear waste is similar to incineration processes and results in the bulk of the waste being reduced in volume and weight to some residual solids termed residue. The residue is composed of various dispersible solid materials and typically contains the resultant radioactivity from the waste. This report describes the immobilization of the residue in portland cement, borosilicate glass, and some other waste forms. Diagrams showing the cement and glass virtification parameters are included in the report as well as process steps and candidate waste product forms. Cement immobilization is simplest and probably least expensive; glass vitrification exhibits the best overall volume reduction ratio
Immobilization of acid digestion residue
International Nuclear Information System (INIS)
Acid digestion treatment of nuclear waste is similar to incineration processes and results in the bulk of the waste being reduced in volume and weight to some residual solids termed ''residue.'' The residue is composed of various dispersible solid materials and typically contains the resultant radioactivity from the waste. This report describes the immobilization of the residue in portland cement, borosilicate glass, and some other waste forms. Diagrams showing the cement and glass vitrification parameters are included in the report as well as process steps and candidate waste product forms. Cement immobilization is simplest and probably least expensive; glass vitrification exhibits the best overall volume reduction ratio
Global mapping of the regulatory interactions of histone residues.
Jung, Inkyung; Seo, Jungmin; Lee, Heun-Sik; Stanton, Lawrence W; Kim, Dongsup; Choi, Jung Kyoon
2015-12-21
Histone residues can serve as platforms for specific regulatory function. Here we constructed a map of regulatory associations between histone residues and a wide spectrum of chromatin regulation factors based on gene expression changes by histone point mutations in Saccharomyces cerevisiae. Detailed analyses of this map revealed novel associations. Regarding the modulation of H3K4 and K36 methylation by Set1, Set2, or Jhd2, we proposed a role for H4K91 acetylation in early Pol II elongation, and for H4K16 deacetylation in late elongation and crosstalk with H3K4 demethylation for gene silencing. The association of H3K56 with nucleosome positioning suggested that this lysine residue and its acetylation might contribute to nucleosome mobility for transcription activation. Further insights into chromatin regulation are expected from this approach. PMID:26602082
A Waveguide Based, High Power Pockels Cell Modulator for Sub-Nanosecond Pulse Slicing Project
National Aeronautics and Space Administration — The Goal of this STTR is to develop a high speed, high power, waveguide based modulator (phase and amplitude) and investigate its use as a pulse slicer. The key...
OTDM-to-WDM Conversion of Complex Modulation Formats by Time-Domain Optical Fourier Transformation
DEFF Research Database (Denmark)
Palushani, Evarist; Richter, T.; Ludwig, R.; Schubert, C.; Mulvad, Hans Christian Hansen; Clausen, Anders; Oxenløwe, Leif Katsuo
2012-01-01
We demonstrate the utilization of the optical Fourier transform technique for serial-to-parallel conversion of 64×10-GBd OTDM data tributaries with complex modulation formats into 50-GHz DWDM grid without loss of phase and amplitude information.
Pavlov, V. F.; Konovalov, G. V.; Minin, B. V.; Kirpichev, V. A.
Results of residual stress measurements and fatigue tests are presented for bolts of VT16 titanium alloy manufactured by various methods. A method is proposed for plotting the maximum-amplitude diagram of the stress cycle of a threaded joint with allowance for the residual stresses in the thread grooves. The calculated results are in good agreement with experimental data.
Loop-quantum-gravity vertex amplitude.
Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo
2007-10-19
Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity. PMID:17995233
Approximate formulas for moderately small eikonal amplitudes
Kisselev, A V
2015-01-01
The eikonal approximation for moderately small scattering amplitudes is considered. With the purpose of using for their numerical estimations, the formulas are derived which contain no Bessel functions, and, hence, no rapidly oscillating integrands. To obtain these formulas, the improper integrals of the first kind which contain products of the Bessel functions J_0(z) are studied. The expression with four functions J_0(z) is generalized. The expressions for the integrals with the product of five and six Bessel functions J_0(z) are also found. The known formula for the improper integral with two functions J_nu(z) is generalized for non-integer nu.
Information transfer with small-amplitude signals
Kostal, Lubomir; 10.1103/PhysRevE.81.050901
2010-01-01
We study the optimality conditions of information transfer in systems with memory in the low signal-to-noise ratio regime of vanishing input amplitude. We find that the optimal mutual information is represented by a maximum-variance of the signal time course, with correlation structure determined by the Fisher information matrix. We provide illustration of the method on a simple biologically-inspired model of electro-sensory neuron. Our general results apply also to the study of information transfer in single neurons subject to weak stimulation, with implications to the problem of coding efficiency in biological systems.
From correlation functions to scattering amplitudes
Eden, Burkhard; Sokatchev, Emery
2010-01-01
We study the correlators of half-BPS protected operators in N=4 super-Yang-Mills theory, in the limit where the positions of the adjacent operators become light-like separated. We compute the loop corrections by means of Lagrangian insertions. The divergences resulting from the light-cone limit are regularized by changing the dimension of the integration measure over the insertion points. Switching from coordinates to dual momenta, we show that the logarithm of the correlator is identical with twice the logarithm of the matching MHV gluon scattering amplitude. We present a number of examples of this new relation, at one and two loops.
Gravity amplitudes from a Gaussian matrix model
Heckman, Jonathan J.; Verlinde, Herman
2013-09-01
We reformulate MHV scattering amplitudes in 4D gauge theory and super- gravity as correlation functions of bilinear operators in a supersymmetric gaussian matrix model. The model retains the symmetries of an S 4 of radius ? and the matrix variables are represented as linear operators acting on a finite-dimensional Hilbert space. Bilinear fields of the model generate a current algebra. In the large N double scaling limit where is held fixed, there is an emergent flat 4D space-time with a built in short distance cutoff.
Gravity Amplitudes from a Gaussian Matrix Model
Heckman, Jonathan J
2011-01-01
We reformulate MHV scattering amplitudes in 4D gauge theory and supergravity as correlation functions of bilinear operators in a supersymmetric gaussian matrix model. The model retains the symmetries of an S(4) of radius L and the matrix variables are represented as linear operators acting on a finite-dimensional Hilbert space. Bilinear fields of the model generate a current algebra. In the large N double scaling limit where l_pl ~ L / sqrt(N) is held fixed, there is an emergent flat 4D space-time with a built in short distance cutoff.
Gravity Amplitudes from a Gaussian Matrix Model
Heckman, Jonathan J.; Verlinde, Herman
2011-01-01
We reformulate MHV scattering amplitudes in 4D gauge theory and supergravity as correlation functions of bilinear operators in a supersymmetric gaussian matrix model. The model retains the symmetries of an S(4) of radius L and the matrix variables are represented as linear operators acting on a finite-dimensional Hilbert space. Bilinear fields of the model generate a current algebra. In the large N double scaling limit where l_pl ~ L / sqrt(N) is held fixed, there is an emer...
The small amplitude magnetohydrodynamic Riemann problem
Wu, C. C.; Kennel, C. F.
1993-01-01
The small-amplitude MHD Riemann problem is studied using the Cohen-Kulsrud-Burgers equations. Unlike the coplanar Riemann problem, the evolution of noncoplanar Riemann problems is not self-similar and its flow structures could change in time. But its large-time behavior is very simple and a time-dependent 2 - 3 intermediate shock is always involved for the noncoplanar field rotations. The time-dependent 2 - 3 intermediate shock has a well-defined structure and exists for any degree of field rotation.
Modulational stability of electron plasma wave spectra
Pécseli, H. L.; Pécseli
2014-10-01
Analytical models for weakly nonlinear electron plasma waves are considered in order to obtain dynamic equations for the space-time evolution of their local power spectra. The model contains the wave kinetic equation as a limiting case for slow, long wavelength modulations. It is demonstrated that a finite spectral width in wavenumbers has a stabilizing effect on the modulational instability. The results invite a simple heuristic relation between the spectral width and the root-mean-square amplitude of stable stationary turbulent Langmuir wave spectra. A non-local average dispersion relation is derived as a limiting form by using the formalism developed for the spectral dynamics.
Terahertz polarization modulator based on metasurface
He, Jingwen; Xie, Zhenwei; Wang, Sen; Wang, Xinke; Kan, Qiang; Zhang, Yan
2015-10-01
Based on the metasurface composed of C-shaped slit (CSS) antennas, a broadband transmitted terahertz (THz) polarization modulator (TPM) is proposed and experimentally verified. By rotating the designed TPM, the amplitudes and phase difference of the two orthogonal electric components can be tuned, and thus the polarization of the transmitted THz beam is modulated. The linear-to-linear and linear-to-elliptical polarization conversion is realized with the proposed TPM. Numerical simulations are also performed and agree well with the experimental measurements. The proposed concept can be applied to other wavebands simply by varying the structure parameters and the material of the substrate.
Hybrid modulation properties of the Epson LCTV
Kirsch, James C.; Loudin, Jeffrey A.; Gregory, Don A.
1991-11-01
Liquid crystal televisions have received extensive attention in literature for use as input and Fourier plane devices in joint transform correlators, and for use in other optical processing architectures requiring television rate inputs. The device has also been used in incoherent optical neural network systems at Penn State University. Recent research investigated the hybrid phase and amplitude modulating properties of the LCTV in a joint transform correlator. A new LCTV made by Epson is the focus of this paper. The hybrid modulation properties of this television will be evaluated and the results presented. Results from applications using the new LCTVs will also be presented.
Photovoltaic module and module arrays
Botkin, Jonathan; Graves, Simon; Lenox, Carl J. S.; Culligan, Matthew; Danning, Matt
2013-08-27
A photovoltaic (PV) module including a PV device and a frame, The PV device has a PV laminate defining a perimeter and a major plane. The frame is assembled to and encases the laminate perimeter, and includes leading, trailing, and side frame members, and an arm that forms a support face opposite the laminate. The support face is adapted for placement against a horizontal installation surface, to support and orient the laminate in a non-parallel or tilted arrangement. Upon final assembly, the laminate and the frame combine to define a unitary structure. The frame can orient the laminate at an angle in the range of 3.degree.-7.degree. from horizontal, and can be entirely formed of a polymeric material. Optionally, the arm incorporates integral feature(s) that facilitate interconnection with corresponding features of a second, identically formed PV module.
Wavelet analysis of wall turbulence to study large-scale modulation of small scales
Baars, W. J.; Talluru, K. M.; Hutchins, N.; Marusic, I.
2015-10-01
Wavelet analysis is employed to examine amplitude and frequency modulations in broadband signals. Of particular interest are the streamwise velocity fluctuations encountered in wall-bounded turbulent flows. Recent studies have shown that an important feature of the near-wall dynamics is the modulation of small scales by large-scale motions. Small- and large-scale components of the velocity time series are constructed by employing a spectral separation scale. Wavelet analysis of the small-scale component decomposes the energy in joint time-frequency space. The concept is to construct a low-dimensional representation of the small-scale time-varying spectrum via two new time series: the instantaneous amplitude of the small-scale energy and the instantaneous frequency. Having the latter in a time-continuous representation allows a more thorough analysis of frequency modulation. By correlating the large-scale velocity with the concurrent small-scale amplitude and frequency realizations, both amplitude and frequency modulations are studied. In addition, conditional averages of the small-scale amplitude and frequency realizations depict unique features of the scale interaction. For both modulation phenomena, the much studied time shifts, associated with peak correlations between the large-scale velocity and small-scale amplitude and frequency traces, are addressed. We confirm that the small-scale amplitude signal leads the large-scale fluctuation close to the wall. It is revealed that the time shift in frequency modulation is smaller than that in amplitude modulation. The current findings are described in the context of a conceptual mechanism of the near-wall modulation phenomena.
On the benefit of DMT modulation in nonlinear VLC systems.
Qian, Hua; Cai, Sunzeng; Yao, Saijie; Zhou, Ting; Yang, Yang; Wang, Xudong
2015-02-01
In a visible light communication (VLC) system, the nonlinear characteristic of the light emitting diode (LED) in transmitter is a limiting factor of system performance. Modern modulation signals with large peak-to-power-ratio (PAPR) suffers uneven distortion. The nonlinear response directly impacts the intensity modulation and direct detection VLC system with pulse-amplitude modulation (PAM). The amplitude of the PAM signal is distorted unevenly and large signal is vulnerable to noise. Orthogonal linear transformations, such as discrete multi-tone (DMT) modulation, can spread the nonlinear effects evenly to each data symbol, thus perform better than PAM signals. In this paper, we provide theoretical analysis on the benefit of DMT modulation in nonlinear VLC system. We show that the DMT modulation is a better choice than the PAM modulation for the VLC system as the DMT modulation is more robust against nonlinearity. We also show that the post-distortion nonlinear elimination method, which is applied at the receiver, can be a reliable solution to the nonlinear VLC system. Simulation results show that the post-distortion greatly improves the system performance for the DMT modulation. PMID:25836125
The Construction of Spin Foam Vertex Amplitudes
Directory of Open Access Journals (Sweden)
Eugenio Bianchi
2013-01-01
Full Text Available Spin foam vertex amplitudes are the key ingredient of spin foam models for quantum gravity. These fall into the realm of discretized path integral, and can be seen as generalized lattice gauge theories. They can be seen as an attempt at a 4-dimensional generalization of the Ponzano-Regge model for 3d quantum gravity. We motivate and review the construction of the vertex amplitudes of recent spin foam models, giving two different and complementary perspectives of this construction. The first proceeds by extracting geometric configurations from a topological theory of the BF type, and can be seen to be in the tradition of the work of Barrett, Crane, Freidel and Krasnov. The second keeps closer contact to the structure of Loop Quantum Gravity and tries to identify an appropriate set of constraints to define a Lorentz-invariant interaction of its quanta of space. This approach is in the tradition of the work of Smolin, Markopoulous, Engle, Pereira, Rovelli and Livine.
Quasi Distribution Amplitude of Heavy Quarkonia
Jia, Yu
2015-01-01
The recently-proposed quasi distributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions (PDF) and distribution amplitudes (DA), directly in the $x$-space. Owing to its excessive simplicity, the heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DA. In the framework of non-relativistic QCD (NRQCD) factorization, we compute the order-$\\alpha_s$ correction to both light-cone distribution amplitudes (LCDA) and quasi-DA associated with the lowest-lying quarkonia, with the transverse momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2-3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the fut...
Getting superstring amplitudes by degenerating Riemann surfaces
Matone, Marco; Volpato, Roberto
2010-11-01
We explicitly show how the chiral superstring amplitudes can be obtained through factorisation of the higher genus chiral measure induced by suitable degenerations of Riemann surfaces. This powerful tool also allows to derive, at any genera, consistency relations involving the amplitudes and the measure. A key point concerns the choice of the local coordinate at the node on degenerate Riemann surfaces that greatly simplifies the computations. As a first application, starting from recent ansätze for the chiral measure up to genus five, we compute the chiral two-point function for massless Neveu-Schwarz states at genus two, three and four. For genus higher than three, these computations include some new corrections to the conjectural formulae appeared so far in the literature. After GSO projection, the two-point function vanishes at genus two and three, as expected from space-time supersymmetry arguments, but not at genus four. This suggests that the ansatz for the superstring measure should be corrected for genus higher than four.
Localized finite-amplitude disturbances and selection of solitary waves
Kliakhandler; Porubov; Velarde
2000-10-01
It turns out that evolution of localized finite-amplitude disturbances in perturbed KdV equation is qualitatively different compared with conventional small-amplitude initial conditions. Namely, relatively fast solitary waves, with one and the same amplitude and velocity, are formed ahead of conventional chaotic-like irregular structures. The amplitude and velocity of the waves, obtained from the asymptotic theory, are in excellent agreement with numerics. PMID:11089043
Dual parametrisation and Abel transform tomography for the DVCS amplitude
International Nuclear Information System (INIS)
We present a way to extract the maximum amount of information about Generalized Parton Distributions (GPDs) from amplitudes of hard exclusive processes. For investigation of the amplitudes we use the dual parametrization of GPDs, which provides us very handy and flexible tool to describe the amplitudes in terms of single function- so-called quintessence function. We show that relation between the quintessence function and the amplitude of the hard exclusive process corresponds to Abel transform tomography.
Amplitude analysis of two-body meson-baryon scattering
International Nuclear Information System (INIS)
Information on high-energy scattering amplitudes is extracted from experimental data for ?N and KN elastic and charge-exchange scattering using model independent methods based on isospin symmetry and analyticity. These analyses provide numerical knowledge of the scattering amplitudes and make it possible to answer the questions: which amplitudes are responsible for the different experimental features, which models are able to produce such amplitudes and to which extent are duality, SU(3) and quark model relations consistent with the experimental data
Supersymmetric Ward Identities and NMHV Amplitudes involving Gluinos
Bidder, S J; Perkins, W B; Bidder, Steven J.; Dunbar, David C.; Perkins, Warren B.
2005-01-01
We show how Supersymmetric Ward identities can be used to obtain amplitudes involving gluinos or adjoint scalars from purely gluonic amplitudes. We obtain results for all one-loop six-point NMHV amplitudes in $\\NeqFour$ Super Yang-Mills theory which involve two gluinos or two scalar particles. More general cases are also discussed.
Closed String Amplitudes in Open String Field Theory
Takahashi, Tomohiko; Zeze, Syoji
2003-01-01
We investigate gauge invariant operators corresponding to on-shell closed string states in open string field theory. Using both oscillator representation and conformal mapping techniques, we calculate a two closed string tachyon amplitude that connects two gauge invariant operators by an open string propagator.We find that this amplitude is in a complete agreement with the usual disc amplitude.