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
Fu, Xiao-fang; Zhao, Gang; Ma, Wei-guang; Tan, Wei; Li, Zhi-xin; Dong, Lei; Zhang, Lei; Yin, Wang-bao; Jia, Suo-tang
2014-06-01
Frequency modulation spectroscopy (FMS) not only can be used to simultaneously measure the absorption and dispersion of atoms and molecules, but is the key technology of the noise immunity cavity enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). The optical devices or the instability of output light polarization of the laser source will induce the residual amplitude modulation (RAM) in the FMS. RAM greatly limits the FMS technology application in trace gas detection, so the research on the RAM characteristics in the FMS has very important significance. Firstly, the lineshape of FMS without absorption was analyzed, and the impact factors on the RAM were acquired, then the influence of input and output polarization direction and electro-optical modulation (EOM) temperature was measured, respectively. They all have linear relationship with the RAM. The results verify the theoretical analysis and provide the basis for reducing the RAM and other related working. PMID:25358144
Amplitude path for a polar modulation transmitter
Jakobsson, Anders
2007-01-01
this is master tesis on characterisation and implementation of amplitude path for a polar modulation transmetter, targeted at bluethooth extended data rate ( EDR).bluethooth EDR uses quadrature modulation techniques to obtain higher data rates. these techniques use ampitude an phase modulation of a carrier to increas bitrate without increasing signal bandwidth compared to anly using amplitude or phas modulation. the amplitude path migjt be futher developed by investigating the use of higjer o...
Amplitude-modulated laser imager.
Mullen, Linda; Laux, Alan; Concannon, Brian; Zege, Eleonora P; Katsev, Iosif L; Prikhach, Alexander S
2004-07-01
Laser systems have been developed to image underwater objects. However, the performance of these systems can be severely degraded in turbid water. We have developed a technique using modulated light to improve underwater detection and imaging. A program, Modulated Vision System (MVS), which is based on a new theoretical approach, has been developed to predict modulated laser imaging performance. Experiments have been conducted in a controlled laboratory environment to test the accuracy of the theory as a function of system and environmental parameters. Results show a strong correlation between experiment and theory and indicate that the MVS program can be used to predict future system performance. PMID:15250554
Speech production in amplitude-modulated noise
DEFF Research Database (Denmark)
Macdonald, Ewen N; Raufer, Stefan
2013-01-01
The Lombard effect refers to the phenomenon where talkers automatically increase their level of speech in a noisy environment. While many studies have characterized how the Lombard effect influences different measures of speech production (e.g., F0, spectral tilt, etc.), few have investigated the consequences of temporally fluctuating noise. In the present study, 20 talkers produced speech in a variety of noise conditions, including both steady-state and amplitude-modulated white noise. While listening to noise over headphones, talkers produced randomly generated five word sentences. Similar to previous studies, talkers raised the level of their voice in steady-state noise. While talkers also increased the level of their voice in amplitude-modulated noise, the increase was not as large as that observed in steady-state noise. Importantly, for the 2 and 4 Hz amplitude-modulated noise conditions, talkers altered the timing of their utterances, reducing the energetic overlap with the masker by approximately 2%. However, for the 1 Hz amplitude-modulated condition, talkers increased the overlap by approximately 4%. Overall, the results demonstrate that talkers are sensitive to the temporal aspects of noisy environments and will alter their speech accordingly.
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
Energy Technology Data Exchange (ETDEWEB)
Burkhart, S.C.; Wilcox, R.B.; Browning, D.; Penko, F.A.
1996-12-17
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 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
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 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. PMID:25523757
Amplitude modulation reflectometry for large fusion devices
International Nuclear Information System (INIS)
One of the main problems which has been present in most reflectometers during the last years is the need for a coherent tracking of the phase delay: fast density fluctuations and strong modulation on the amplitude of the reflected signal usually produce ''fringe jumps'' in the phase signal. In such a situation the ''history'' of the phase evolution is lost and big errors can arise in the determination of the density profile. This problem will become more severe in large fusion devices, operating at high densities with high magnetic field: the cutoff wavelength becomes shorter and the phase delays involved become larger as well as the effect of the broadband fluctuations. Amplitude modulation reflectometry performs a time delay measurement by the determination of the phase delay of the modulating envelope of a millimeter wave beam reflected at the plasma. The phase delays involved are in the range <2? and the measurement is not negatively affected by the broadband fluctuations. The phase readout can be directly obtained without complicated fringe counters: the method provides a promising possibility for real time determination of the plasma position and density profile, which will be very important for the next step devices (ITER-NET). (author) 2 refs., 3 figs
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.)
Honma, Satoshi; Sekiguchi, Toru
2014-09-01
The utilization of spatial quadrature amplitude modulation (SQAM) signals with amplitude and phase modulation is a simple method used to improve storage capacity in a holographic data storage system. We propose a multilevel phase and amplitude modulation method for holographic memories with a programmable phase modulator (PPM). In this method, holographic page data is recorded by a two-step exposure process for different phase-modulated data. There is no need to adjust the positions of spatial light modulators (SLM) with high accuracy because we use only one spatial modulator. We estimate the quality of 16 SQAM signals produced by our technique.
Log-Likelihood Classification Of Quadrature Amplitude Modulation
Directory of Open Access Journals (Sweden)
Savita Kamboj
2013-10-01
Full Text Available This paper is concerned with amplitude-based log likelihood classification for quadrature amplitude modulation. We derive the amplitude density functions of received QAM signals first, then develop the required statistics for signal classification based on the maximum a posteriori probability criterion and demonstrate a schematic structure of classifier for M-ary QAM signals. It is illustrated successful classification rate reaches 100% for SNR>=15.
Amplitude modulated sinusoidal signal decomposition for audio coding
DEFF Research Database (Denmark)
Christensen, Mads GræsbØll; Jakobsson, Andreas
2006-01-01
In this letter, we present a decomposition for sinusoidal coding of audio, based on an amplitude modulation of sinusoids via a linear combination of arbitrary basis vectors. The proposed method, which incorporates a perceptual distortion measure, is based on a relaxation of a nonlinear least-squares minimization. Rate-distortion curves and listening tests show that, compared to a constant-amplitude sinusoidal coder, the proposed decomposition offers perceptually significant improvements in critical transient signals.
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.
Resonance fluorescence spectrum of intense amplitude modulated laser light
Blind, B.; Fontana, P. R.; Thomann, Pierre
2010-01-01
The spectrum of light scattered by a two-level atom in an intense laser beam with amplitude modulated light is calculated. The spectrum is obtained by evaluating the Fourier transform of the autocorrelation function of the dipole moment. The modulation introduces new components in both the coherent and incoherent parts of the frequency distribution. The total intensity when plotted as a function of the average Rabi frequency exhibits parametric resonances.
Ito, Kazuhito; Nakagawa, Seiji
2015-07-01
A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AM-BCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal.
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.
Demodulation techniques for the amplitude modulated laser imager.
Mullen, Linda; Laux, Alan; Cochenour, Brandon; Zege, Eleonora P; Katsev, Iosif L; Prikhach, Alexander S
2007-10-20
A new technique has been found that uses in-phase and quadrature phase (I/Q) demodulation to optimize the images produced with an amplitude-modulated laser imaging system. An I/Q demodulator was used to collect the I/Q components of the received modulation envelope. It was discovered that by adjusting the local oscillator phase and the modulation frequency, the backscatter and target signals can be analyzed separately via the I/Q components. This new approach enhances image contrast beyond what was achieved with a previous design that processed only the composite magnitude information. PMID:17952171
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.
Cluster incorporation during amplitude modulated VHF discharge silane plasmas
Toko, Susumu; Kim, Yeonwon; Hashimoto, Yuji; Kanemitu, Yoshinori; Seo, Hyunwoong; Uchida, Giichiro; Kamataki, Kunihiro; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu
2013-09-01
VHF discharge silane plasmas have been widely used to deposit hydrogenated amorphous silicon (a-Si:H) films. In this plasma process, while the higher VHF power brings about the higher deposition rate, it also results in generating a lot of Si clusters, which are mainly responsible for light degradation of a-Si:H thin films. Therefore, it is important to clarify a growing process and behavior of clusters and to develop a method for suppressing cluster incorporation into films. Here we investigated effects of amplitude modulated VHF discharge silane plasmas on cluster incorporation into Si thin films by in-situ measurements with quartz crystal microbalances (QCM). Experiments were carried out in a multi-hollow discharge plasma CVD reactor with QCM. The amount of cluster incorporation in initial phase and steady state is found to be controlled by modulation level and frequency of the amplitude modulation. VHF discharge silane plasmas have been widely used to deposit hydrogenated amorphous silicon (a-Si:H) films. In this plasma process, while the higher VHF power brings about the higher deposition rate, it also results in generating a lot of Si clusters, which are mainly responsible for light degradation of a-Si:H thin films. Therefore, it is important to clarify a growing process and behavior of clusters and to develop a method for suppressing cluster incorporation into films. Here we investigated effects of amplitude modulated VHF discharge silane plasmas on cluster incorporation into Si thin films by in-situ measurements with quartz crystal microbalances (QCM). Experiments were carried out in a multi-hollow discharge plasma CVD reactor with QCM. The amount of cluster incorporation in initial phase and steady state is found to be controlled by modulation level and frequency of the amplitude modulation. Work supported by NEDO and PVTEC.
Focusing Light through Random Photonic Media by Binary Amplitude Modulation
Akbulut, Duygu; van Putten, Elbert G; Vos, Willem L; Mosk, Allard P
2011-01-01
We study the focusing of light through random photonic materials using wavefront shaping. We explore a novel approach namely binary amplitude modulation. To this end, the light incident to a random photonic medium is spatially divided into a number of segments. We identify the segments that give rise to fields that are out of phase with the total field at the intended focus and assign these a zero amplitude, whereas the remaining segments maintain their original amplitude. Using 812 independently controlled segments of light, we find the intensity at the target to be 75 +/- 6 times enhanced over the average intensity behind the sample. We experimentally demonstrate focusing of light through random photonic media using both an amplitude only mode liquid crystal spatial light modulator and a MEMS-based spatial light modulator. Our use of Micro Electro-Mechanical System (MEMS)-based digital micromirror devices for the control of the incident light field opens an avenue to high speed implementations of wavefront ...
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.
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.
Noncollinear amplitude-modulated magnetic order in Gd compounds
Rotter, M.; Loewenhaupt, M.; Doerr, M.; Lindbaum, A.; Michor, H.
2001-07-01
In the present work a model within the mean-field theory is developed in order to analyze the specific heat of magnetically ordered systems. This model allows to draw conclusions about the type of magnetic structure from the specific heat near the magnetic transition. The known description of collinear amplitude-modulated and equal-moment magnetism has been extended to account for noncollinear amplitude-modulated (NCAM) antiferromagnetic order by introducing an anisotropic exchange interaction. Experimental evidence for NCAM order is expected from measurements of the specific-heat anomaly at the ordering temperature and from magnetic scattering experiments. The specific heat of GdCu2 was measured and analyzed within the model and a good agreement is reached. Furthermore, the specific heat of other noncollinear Gd antiferromagnets near the ordering temperature has been calculated and is compared to available experimental data.
Amplitude modulation control of escape from a potential well
International Nuclear Information System (INIS)
We demonstrate the effectiveness of periodic amplitude modulations in controlling (suppressing and enhancing) escape from a potential well through the universal model of a damped Helmholtz oscillator subjected to an external periodic excitation (the escape-inducing excitation) whose amplitude is periodically modulated (the escape-controlling excitation). Analytical and numerical results show that this multiplicative control works reliably for different subharmonic resonances between the two periodic excitations involved, and that its effectiveness is comparable to those of different methods of additive control. Additionally, we demonstrate the robustness of the multiplicative control against the presence of low-intensity Gaussian noise. -- Highlights: •Multiplicative control of escape from a potential well has been demonstrated. •Theoretical predictions are obtained from a Melnikov analysis. •It has been shown the robustness of the multiplicative control against noise.
Amplitude modulation of vowel glottal pulses: application to sleep inertia
Ruiz, Robert; Plantin De Hugues, Philippe; LEGROS, CLAUDE
2012-01-01
Human voice carries non-linguistic information about emotion, fatigue, stress, truth, psychological illnesses etc. The proofs of this are well-established nowadays. In real-life situations, in laboratory conditions and from a cross-cultural point of view, the speaker?s psycho-physiological disorders induce vocal modifications. Many acoustic parameters are measured. They belong to the dynamic and spectral planes. Phase space is also involved. Amplitude modulation is one of them. Unlike prosod...
Quantifying dielectrophoretic nanoparticle response to amplitude modulated input signal
International Nuclear Information System (INIS)
A new experimental system and theoretical model have been developed to systematically quantify and analyse the movement of nanoparticles subjected to continuously pulsed, or amplitude modulated, dielectrophoretic (DEP) input signal. Modulation DEP-induced concentration fluctuations of fluorescently labelled 0.5 µm and 1.0 µm diameter latex nanospheres, localized near castellated electrode edges, were quantified using real-time fluorescence microscope dielectrophoretic spectroscopy. Experimental measurements show that the fluorescence fluctuations decrease as the modulation frequency increases-in agreement with model predictions. The modulation frequency was varied from 25 × 10-3 to 25 Hz and the duty-cycle ratios ranged from zero to unity. Two new parameters for characterizing DEP nanoparticle transport are defined: the modulation frequency bandwidth and the optimal duty-cycle ratio. The ‘on/off’ modulation bandwidth, for micrometre scale movement, was measured to be 0.6 Hz and 1.0 Hz for 1.0 µm and 0.5 µm diameter nanospheres, respectively. At these cut-off frequencies very little movement of the nanospheres could be microscopically observed. Optimal fluorescence fluctuations, for modulation frequencies ranging from 0.25 to 1.0 Hz, occurred for duty-cycle ratio values ranging from 0.3 to 0.7-agreeing with theory. The results are useful for automated DEP investigations and associated technologies.
Amplitude modulation of atomic wave functions. Final report
International Nuclear Information System (INIS)
The major theoretical advance has been to show that one can modulate Rydberg wave functions using either of two methods: (1) the amplitude modulation technique which depends on autoionization to deplete part of the wave function, or (2) a phase modulation method, which uses a change in the core potential to create a localized phase shift in the wave function. Essentially, these two methods can both be seen as using the core potential to change the Rydberg wave function, using the imaginary part of the potential to do amplitude modulation, or using the real part of the potential to do phase modulation. This work will be published as the authors acquire experimental results which show the differences between the two methods. One of the results of this theoretical study is that the initial proposal to study Barium 6snd states had a significant flaw. Neither the autoionization time, nor the quantum defect shifts are very large in these cases. This means that the modulation is relatively small. This shows itself primarily in the difficulty of seeing significant population redistribution into different 6snd states. The authors intend to correct this in the next funding cycle either: (a) by using the more quickly decaying Ba 6pnf states to modulate 6snd states, or (b) by using Sr 5 snd states, as outlined in this report. Their first, low power experiments are complete. These experiments have used two pulses to do a temporal version of the Ramsey separated oscillatory fields excitation. The two pulses are generated by passing the single pulse through a Michelson-Morley interferometer, which is computer controlled to sweep one arm through 2.5 microm in steps of 10 nm. The second pulse's excitation interferes with that of the first pulse, and so the total excitation has a sinusoidal variation (with a time period equal to the optical period) on top of a constant background. The amplitude of the total variation should decay at half of the rate decay rate of the autoionizing state, so this produces a time-resolved measurement of the very rapid autoionization decay. Although this does not yet show that the atom stores modulations in the bound coherent state, it does demonstrate that the atom can be excited to an autoionizing state with high efficiency, and then brought back to a bound state at a later time. The second set of experiments takes the previous work to the strong coupling regime
Molecular dynamics simulation of amplitude modulation atomic force microscopy.
Hu, Xiaoli; Egberts, Philip; Dong, Yalin; Martini, Ashlie
2015-06-12
Molecular dynamics (MD) simulations were used to model amplitude modulation atomic force microscopy (AM-AFM). In this novel simulation, the model AFM tip responds to both tip-substrate interactions and to a sinusoidal excitation signal. The amplitude and phase shift of the tip oscillation observed in the simulation and their variation with tip-sample distance were found to be consistent with previously reported trends from experiments and theory. These simulation results were also fit to an expression enabling estimation of the energy dissipation, which was found to be smaller than that in a corresponding experiment. The difference was analyzed in terms of the effects of tip size and substrate thickness. Development of this model is the first step toward using MD to gain insight into the atomic-scale phenomena that occur during an AM-AFM measurement. PMID:25990713
Molecular dynamics simulation of amplitude modulation atomic force microscopy
Hu, Xiaoli; Egberts, Philip; Dong, Yalin; Martini, Ashlie
2015-06-01
Molecular dynamics (MD) simulations were used to model amplitude modulation atomic force microscopy (AM-AFM). In this novel simulation, the model AFM tip responds to both tip–substrate interactions and to a sinusoidal excitation signal. The amplitude and phase shift of the tip oscillation observed in the simulation and their variation with tip–sample distance were found to be consistent with previously reported trends from experiments and theory. These simulation results were also fit to an expression enabling estimation of the energy dissipation, which was found to be smaller than that in a corresponding experiment. The difference was analyzed in terms of the effects of tip size and substrate thickness. Development of this model is the first step toward using MD to gain insight into the atomic-scale phenomena that occur during an AM-AFM measurement.
Dispersion interferometer using modulation amplitudes on LHD (invited)
Energy Technology Data Exchange (ETDEWEB)
Akiyama, T., E-mail: takiyama@lhd.nifs.ac.jp; Yasuhara, R.; Kawahata, K. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292 (Japan); Okajima, S.; Nakayama, K. [Chubu University, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan)
2014-11-15
Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup ?3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup ?3} can be overcome by a sufficient sampling rate of about 100 kHz.
International Nuclear Information System (INIS)
During propagating in Nd-glass amplifiers, the spectra of the broadband laser pulses are modulated due to gain narrowing and gain saturation effects, resulting in loss of sidebands and unbalance of the spectra, and further leading to the temporal intensity modulation. The amplitude modulations (AMs) have been numerically simulated for different broadband laser sources. The effects of the gain bandwidth, the laser bandwidth, as well as the deviation of central wavelength between the laser source and amplifier of the AMs have been analyzed. Results indicate that all of the different broadband laser sources discussed in this paper exhibit more or less AMs, and the temporal intensity modulation of stacked chirped pulses is smaller than that of sinusoidally frequency-modulated pulses. (authors)
Shuttle extravehicular activity signal processor pulse amplitude modulation decommutator
Noble, D. E.; Conrad, W. M.
1974-01-01
To provide data with long-term stability and accuracy, the pulse amplitude modulation (PAM) decommutator was synchronized to the PAM-return to zero wavetrain, and each channel was sampled with a common sample and hold circuit and digitized sequentially. The digital value of each channel was then scaled by the digital value of the calibration channels. The corrected digital value of each channel was stored for one complete frame and then transferred to the multiplexer-demultiplexer at a high rate in one block of serial digital data. A test model was built to demonstrate this design approach taken for the PAM decom and performance data was provided. The accuracies obtained with various signal to noise ratios are shown.
Amplitude Modulation Mode of Scanning Ion Conductance Microscopy.
Li, Peng; Liu, Lianqing; Yang, Yang; Zhou, Lei; Wang, Dong; Wang, Yuechao; Li, Guangyong
2015-08-01
Live-cell imaging at the nanoscale resolution is a hot research topic in the field of life sciences for the direct observation of cellular biological activity. Scanning ion conductance microscopy (SICM) is one of the few effective imaging tools for live-cell imaging at the nanoscale resolution. However, there are various problems in existing scanning modes. The hopping and AC modes suffer from low speed, whereas the DC mode is prone to instability because of the DC drift and external electrical interference. In this article, we propose an amplitude modulation (AM) mode of SICM, which employs an AC voltage to enhance the stability and improve the scanning speed. In this AM mode, we introduce a capacitance compensation method to eliminate capacitance effect and use the amplitude of the AC current component to control the tip movement. Experimental results on polydimethylsiloxane samples verify the validity of the AM mode and demonstrate an improved performance of both speed and stability of this new mode. PMID:25759185
DEFF Research Database (Denmark)
Blaaberg, SØren; MØrk, Jesper
2009-01-01
We present theoretical results that show conversion of phase modulated signals to amplitude modulated signals in an SOA. Large-signal and small-signal calculations show significant conversion responses caused by even minute reflections at the end mirrors.
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.
Residual fatigue life estimation using a nonlinear ultrasound modulation method
Piero Malfense Fierro, Gian; Meo, Michele
2015-02-01
Predicting the residual fatigue life of a material is not a simple task and requires the development and association of many variables that as standalone tasks can be difficult to determine. This work develops a modulated nonlinear elastic wave spectroscopy method for the evaluation of a metallic components residual fatigue life. An aluminium specimen (AA6082-T6) was tested at predetermined fatigue stages throughout its fatigue life using a dual-frequency ultrasound method. A modulated nonlinear parameter was derived, which described the relationship between the generation of modulated (sideband) responses of a dual frequency signal and the linear response. The sideband generation from the dual frequency (two signal output system) was shown to increase as the residual fatigue life decreased, and as a standalone measurement method it can be used to show an increase in a materials damage. A baseline-free method was developed by linking a theoretical model, obtained by combining the Paris law and the Nazarov–Sutin crack equation, to experimental nonlinear modulation measurements. The results showed good correlation between the derived theoretical model and the modulated nonlinear parameter, allowing for baseline-free material residual fatigue life estimation. Advantages and disadvantages of these methods are discussed, as well as presenting further methods that would lead to increased accuracy of residual fatigue life detection.
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.
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.
Sambaraju, Rakesh; Polo, Valentín; Corral, Juan Luis; Martí, Javier
2008-08-15
A novel photonic-vector modulator architecture for the generation of 16 quadrature amplitude modulation (16 QAM) millimeter-wave carriers using dual-drive Mach-Zehnder modulators is proposed. Experimental generation of 5 Gbits/s 4 amplitude shift-keying (4 ASK) and 10 Gbits/s 16 QAM modulated 42 GHz carriers is reported. The multilevel modulated millimeter-wave signals are demodulated using an electrical receiver and its error-vector magnitude (EVM) estimated from the measurements, obtaining EVMs of -21.04 and -18.33 dB for 4 ASK and 16 QAM modulation formats, respectively. PMID:18709104
Analyses of the mechanisms of amplitude modulation of aero-acoustic wind turbine sound
DEFF Research Database (Denmark)
Fischer, Andreas; Aagaard Madsen, Helge
2014-01-01
This paper explores the source mechanism which cause amplitude modulation of the emitted sound of a wind turbine at large distances from the turbine, named as other amplitude modulation. Measurements of the fluctuating surface pressure on a 2.3MW wind turbine showed a considerable variation over a blade revolution in the presence of angle of attack variations. If the blade undergoes transient stall, the variation of the surface pressure spectrum was enhanced and shifted to frequencies below 200Hz. The surface pressure spectra could be directly related to the emitted far eld sound. These ndings give further evidence that transient stall is a main mechanism to cause other amplitude modulation. Wind shear was identified as a critical condition to cause angle of attack variations. Dierent control strategies to mitigate other amplitude modulation were proposed.
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.
Optimization of phase contrast in bimodal amplitude modulation AFM.
Damircheli, Mehrnoosh; Payam, Amir F; Garcia, Ricardo
2015-01-01
Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes. PMID:26114079
International Nuclear Information System (INIS)
In the present work the sensitivity of calculated ??-decay amplitudes to a realistic residual interaction is analyzed in the framework of the approach of O. A. Rumyantsev and M. H. Urin, Phys. Lett. B 443, 51 (1998). and V. A. Rodin, M. H. Urin, and A. Faessler, Nucl. Phys. A 747, 297 (2005). Both the Gamow-Teller (GT) and Fermi (F) matrix elements M2? for two-neutrino ?? decay (2??? decay), along with the monopole transition contributions to the total matrix elements M0? of neutrinoless ?? decay (0??? decay), are calculated within the quasiparticle random-phase approximation (QRPA). In the aforementioned approach decompositions of M2? and M0? can be obtained in terms of the corresponding energy-weighted sum rules S. It is shown that in most of the cases almost the whole dependence of M2? and M0? on the particle-particle (p-p) renormalization parameter gpp is accounted for by the gpp dependence of the corresponding sum rules S. General expressions relating S to a realistic residual particle-particle interaction are derived, which show a pronounced sensitivity of S to the singlet-channel interaction in the case of F transitions and to the triplet-channel interaction in the case of GT transitions. Thus, the sensitivity of M2? and M0? to the SU(4)-symmetry-breaking part of the p-p residual interaction is dictated by the generic structure of theneric structure of the ??-decay amplitudes. Therefore, a choice of this part in a particular calculation needs a special caution. Finally, a better isospin-consistent way of renormalization of a realistic residual p-p interaction to use in QRPA calculations is suggested.
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
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...
Uncovering signals from measurement noise by electro mechanical amplitude modulation
International Nuclear Information System (INIS)
We present an electromechanical parametric scheme to improve the low-frequency signal-to-noise ratio of energy buffering type transducers. The method is based on periodic modulation of the stiffness in the sensory system which produces upconverted replicas of the signals of interest at frequencies where measurement is less troubled by noise or other detrimental effects. We demonstrate this principle by means of capacitive biomimetic hair flow sensors, where we modulate the rotational spring stiffness by periodic electrostatic spring softening, such that a replica of the original signal is formed around the modulation frequency. Using this replica we gain up to a 25-fold improvement of the low-frequency signal-to-noise ratio and sensing threshold. For transient measurements we demonstrate that tiny signals, which are below the noise-levels in the base-band, are revealed well when upconverted to higher frequencies. (paper)
A novel amplitude modulated triangular carrier gain linearization technique for SPWM inverter
Ramkumar Subburam; Jeevananthan Seenithangam; Kamaraj Vijayarajan
2009-01-01
This paper presents a new method to extend the linearity of the sinusoidal pulse width modulation (SPWM) to full range of the pulse dropping region. The proposed amplitude modulated triangular carrier PWM method (AMTCPWM) increases the dynamic range of the SPWM control and eliminates the need of nonlinear modulation in the pulse dropping region to reach the square wave boundary. The novel method combines the spectral quality of SPWM with the efficient single-mode linear control. A simple anal...
Hermitian $(a, b)$-modules and Saito's "higher residue pairings"
Karwasz, Piotr P
2011-01-01
Following the work of Daniel Barlet ([Bar97]) and Ridha Belgrade ([Bel01]) the aim of this article is the study of the existence of $(a, b)$-hermitian forms on regular $(a, b)$-modules. We show that every regular $(a,b)$-module with a non-degenerate bilinear form can be written in an unique way as a direct sum of $(a, b)$-modules $E_i$ that admit either an $(a, b)$-hermitian or an $(a, b)$-anti-hermitian form or both; all three cases are equally possible with explicit examples. As an application we extend the result in [Bel01] on the existence for all $(a, b)$-modules $E$ associated with the Brieskorn module of a holomorphic function with an isolated singularity, of an $(a,b)$-bilinear non degenerate form on $E$. We show that with a small transformation Belgrade's form can be considered $(a, b)$-hermitian and that the result satis es the axioms of Kyoji Saito's "higher residue pairings".
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)
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
Morozov, Oleg G.; Morozov, Gennady A.; Il'in, German I.; Il'in, Alexander G.
2015-03-01
In this paper, we try to analyze ways and means of amplitude-phase modulation conversion of the optical carrier, measuring "amplitude-frequency" and optical-electronic conversion of the obtained spectral components and their use for the measurement of the instantaneous frequency of microwave signals. The aim of paper is to extend the range of measured frequencies, increase the resolution of the measurements in the "low" frequencies and sensitivity of the measurements in the field of "high" frequencies.
Amplitude modulation of electron plasma waves in a quantum plasma
International Nuclear Information System (INIS)
Using the one dimensional quantum hydrodynamic model for a two-component electron-ion dense quantum plasma the linear and nonlinear properties of electron plasma waves are studied including ion motion. By using the standard method of multiple scales perturbation technique a nonlinear Schroedinger equation containing quantum effects is derived. From this equation it is shown that with immobile ions an electron plasma wave becomes modulationally unstable in two distinct regions of the wavenumber. Numerical calculation shows that the stability domain of the wavevector shrinks with the increase in quantum diffraction effect. It is also found that the growth rate of instability in the high wavenumber region increases with the increase in quantum effect. Ion motion is found to have significant effect in changing the stability/instability domains of the wavenumber in the low k-region.
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.
Basic causes of amplitude modulation in climatic/weather parameters
International Nuclear Information System (INIS)
The continuous interaction between the Earth's spinning motion and energy from the Sun gives rise to some (heat) energy oscillations in the Earth-atmosphere system (Njau, 1985a; 1985b; 1986a; 1986b). Recent results of large scale analysis of East African climatic records have proved that these oscillations significantly link the Sun to climatic/weather variations by systematically modulating key climatic/weather parameters like rainfall and air temperature (Njau, 1987a; 1987b; 1987c; 1987e; 1987f). In this paper, we re-develop the latter proof using a very different approach based upon theoretical analysis. The analysis has confirmed a general law suggested earlier (Njau, 1987d), that, with an exception of the diurnal cycle, any permanent cycle in the net solar energy incident upon a given part of the Earth-Atmosphere system gives rise to a quasi-permanent cycle whose period is approximately twice that of the former. Quasi-biennial as well as double sunspot cycles are shown to be a possible result of this general law. (author). 35 refs, 1 fig., 2 tabs
International Nuclear Information System (INIS)
Universal effect of relaxation of charged particle phase oscillations in accelerating waves has been investigated for the case of relativistic particles in amplitude-modulated waves with phase velocity higher than light velocity. Consideration was carried out both on the basis of averaged equations of motion and by means of adiabatic invariants. Damping decrement has been found in a linear approximation
Super-oscillation focusing lens based on continuous amplitude and binary phase modulation.
Wen, Zhongquan; He, Yinghu; Li, Yuyan; Chen, Li; Chen, Gang
2014-09-01
In this paper, we numerically demonstrate the advantage of utilizing continuous amplitude and phase modulation in super-oscillation focusing lens design. Numerical results show that compared with simple binary amplitude modulation, continuous amplitude and phase modulation can greatly improve the super-oscillation focusing performance by increasing the central lobe intensity and the ratio of its energy to the total energy, reducing the sidelobe intensity, and substantially extending the field of view. Our study also reveals the role of phase distribution in reducing the spatial frequency bandwidth of the super-oscillation optical field on the focal plane. Based on continuous amplitude and binary phase modulation, a lens was designed with double layer metal slit array for wavelength of 4.6 µm. COMSOL is used to carry out the 2D simulation. The lens focal length is 40.18? and the focal spot FWHM is 0.308?. Two largest sidelobes are located right next to the central lobe with intensity about 40% of the central lobe intensity. Except for the two sidelobes, other sidelobes have intensity less than 25% of the central lobe intensity, which leads to a clear field of view on the whole focal plane. PMID:25321591
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.
Directory of Open Access Journals (Sweden)
Mark S. Leeson
2007-03-01
Full Text Available
Modulation techniques have attracted increasing attention in optical wireless communications. Basic schemes such as on off keying (OOK, pulse amplitude modulation (PAM and pulse position modulation (PPM have been validated as suitable for the optical wireless channel. This paper starts from the analysis of these three modulation schemes in terms of their power and bandwidth requirements. As a result, a new tunable hybrid modulation technique is proposed. The proposed modulation scheme takes the real time channel conditions into account, which is different from other schemes. By employing amplitude and position modulation selectively, a guaranteed system performance can be secured, without compromising power and bandwidth efficiency. This is also a new approach to realize reliable optical wireless links.
Terminal residue hydrophobicity modulates transmembrane helix-helix interactions.
Ng, Derek P; Deber, Charles M
2014-06-17
Central to the formation of tertiary structure in membrane protein folding is the presence of amino acid sequence motifs (such as "small-XXX-small" segments) in the TM segments that promote interaction-compatible surfaces through which the TM ?-helices interact. Here, we sought to elucidate additional factors that may work in tandem to dictate the ultimate interaction fate of TM-embedded segments. In this context, we used proteolipid protein (PLP), the major protein from central nervous system myelin for which mutant-dependent non-native oligomerization has been implicated in neurological disorders, to explore the specific effects of TM boundary residues (the membrane entry and exit points), keying on the secondary structure and self-association of peptides corresponding to the PLP TM2 ?-helix (wild-type sequence ??AFQYVIYGTASFFFLYGALLLAEGF??). Using gel electrophoresis, circular dichroism, and Förster resonance energy transfer in the membrane-mimetic detergent sodium dodecyl sulfate (SDS), we found that mutation of F90 to residues such as A, I, L, or V maintains the onset of TM2-TM2 dimerization, whereas mutation to E, G, Q, N, S, or T abrogates dimer formation. We attribute this sensitivity to changes in local hydrophobicity, viz., a decrease in hydrophobicity reduces local lipid-peptide interactions, which in turn disrupts peptide ?-helicity and hence the effectiveness of an incipient interaction-compatible surface. Our results show that the secondary structure and oligomeric state of PLP TM2 Lys-tagged peptides are significantly modulated by the specific nature of their C-terminal boundary residue, thus providing insight as to how point mutations, particularly where they produce disease states, can compromise the folding process. PMID:24857611
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.
Discrimination of amplitude-modulated synthetic echo trains by an echolocating bottlenose dolphin.
Dankiewicz, Lois A; Helweg, David A; Moore, Patrick W; Zafran, Justine M
2002-10-01
Bottlenose dolphins (Tursiops truncatus) have an acute ability to use target echoes to judge attributes such as size, shape, and material composition. Most target recognition studies have focused on features associated with individual echoes as opposed to information conveyed across echo sequences (feature envelope of the multi-echo train). One feature of aspect-dependent targets is an amplitude modulation (AM) across the return echoes in the echo train created by relative movement of the target and dolphin. The current study examined whether dolphins could discriminate targets with different AM envelopes. "Electronic echoes" triggered by a dolphin's outgoing echolocation clicks were manipulated to create sinusoidal envelopes with varying AM rate and depth. Echo trains were equated for energy, requiring the dolphin to extract and retain information from multiple echoes in order to detect and report the presence of AM. The dolphin discriminated amplitude-modulated echo trains from those that were not modulated. AM depth thresholds were approximately 0.8 dB, similar to other published amplitude limens. Decreasing the rate of modulation from approximately 16 to 2 cycles per second did not affect the dolphin's AM depth sensitivity. The results support multiple-echo processing in bottlenose dolphin echolocation. This capability provides additional theoretical justification for exploring synthetic aperture sonar concepts in models of animal echolocation that potentially support theories postulating formation of images as an ultimate means for target identification. PMID:12398475
Detection of amplitude-modulated tones by frogs: implications for temporal processing mechanisms.
Hillery, C M
1984-05-01
The whole nerve action potential (AP) from the auditory nerve and midbrain averaged evoked potential (AEP) were recorded in Hyla chrysoscelis and H. versicolor in response to synthesized amplitude-modulated stimuli with variable modulation frequencies (Fm). The AP from these frogs is similar to the potential described for mammals and showed a bandpass characteristic in its ability to follow sinusoidally amplitude-modulated (AM) sound stimuli. A lesioning study suggests that the midbrain AEP is a localized neural response of neurons near the ventral border of the torus semicircularis. The AEP is a complex waveform consisting of fast and slow components. The fast component encodes the temporal structure of acoustic stimuli and is used to measure temporal sensitivity in these two species. The AEP behaves like a low-pass filter with a cutoff frequency of 250 Hz when tracking AM signals. Threshold for detection requires a modulation depth of 8-12% of the total stimulus amplitude (delta I = 1.5-2.0 dB). Relative to the eighth nerve AP, the AEP displays an enhanced coding of AM signals when Fm less than 100 Hz, and a slightly inferior ability to code Fm above 250 Hz. The AEP reflects only that portion of the neural response that encodes amplitude fluctuations. In comparison to the range of amplitude fluctuations coded by single units in the rat inferior colliculus or by human evoked potential, the frog AEP codes higher rates of Fm. The proposal that these frogs process AM stimuli solely on the basis of amplitude fluctuations, and do not use spectral cues at higher modulation frequencies is considered. The AM sensitivity of the AEP, which encompasses most biologically relevant rates of amplitude fluctuation for the animal, and the limited frequency resolution of the periphery, lend support to this proposal. However, convergent spectral processing at higher auditory centers cannot be excluded by this study. Psychophysical tests will be required to determine whether both of these mechanisms may be operating during temporal information processing in anurans. PMID:6746427
Traveling wave amplitude modulator with 1-GHz bandwidth for coherent light optical communication.
Adhav, S R; Adhav, R S; van de Vaart, H
1981-03-01
Two electrooptic materials, deuterated cesium dihydrogen arsenate (D-CDA, CsD(2)AsO(4)) and lithium tanta-late (LiTaO(3)), are examined for the application of a traveling wave-type coherent light modulator. The main design goals are (a) low drive power of 4 W for 10% linear amplitude modulation; (b) +/-3-dB bandwidth of 1 GHz; and (c) 50-Omega impedance. Experimental performance based on theoretical expectations are presented for both materials. Using a microwave network analyzer, the results indicate that the D-CDA modulator gives better performance with a VSWR of 1.06 as compared with the LiTaO(3) modulator figure of 1.23. Direct Current contrast ratio measurements for D-CDA and LiTaO(3) were 50:1 and 20:1, respectively. PMID:20309220
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
Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation
DEFF Research Database (Denmark)
Sosnovtseva, Olga; Pavlov, A.N.
2004-01-01
Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental data from normotensive and hypertensive rats showing different oscillatory patterns and to simulation results obtained from a physiologically based model of the nephron pressure and flow control. We reveal a nonlinear interaction between the two mechanisms that regulate the renal blood flow in the form of frequency and amplitude modulation of the myogenic oscillations.
Improving the performance of bright quantum dot single photon sources using amplitude modulation
Ates, Serkan; Gulinatti, Angelo; Rech, Ivan; Badolato, Antonio; Srinivasan, Kartik
2012-01-01
Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit non-ideal behavior. Here, we demonstrate that amplitude modulation can improve the performance of quantum-dot-based sources. Starting with a bright source consisting of a single quantum dot in a fiber-coupled microdisk cavity, we use synchronized amplitude modulation to temporally filter the emitted light. We observe that the single photon purity, temporal overlap between successive emission events, and indistinguishability can be greatly improved with this technique. As this method can be applied to any triggered single photon source, independent of geometry and after device fabrication, it is a flexible approach to improve the performance of solid-state systems, which often suffer from excess dephasing and multi-photon background emission.
Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation
Sosnovtseva, O. V.; Pavlov, A. N.; Mosekilde, E.; Holstein-Rathlou, N.-H.; Marsh, D. J.
2004-09-01
Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental data from normotensive and hypertensive rats showing different oscillatory patterns and to simulation results obtained from a physiologically based model of the nephron pressure and flow control. We reveal a nonlinear interaction between the two mechanisms that regulate the renal blood flow in the form of frequency and amplitude modulation of the myogenic oscillations.
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...
Amplitude and phase modulation analysis methods for early detection of gear faults
Nicks, J. E.; Krishnappa, G.
This paper presents methods of analysis of vibration data for detecting gear tooth damage using amplitude and phase modulation techniques. Based on examined vibration data from a gear test rig, these methods appear to be effective and reliable diagnostics tools. All stages of gear tooth damage - light, intermediate, and advanced - were detected. A number of processing enhancements to improve the fault detection rate are discussed. These techniques were found to be useful for both discrete and distributed tooth damage.
Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation
Sosnovtseva, Olga; Pavlov, A. N.; Mosekilde, Erik; Holstein-Rathlou, N. -H.; Marsh, D J
2004-01-01
Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental...
Lin, C.-C. K.; Liu, W.-C.; Chan, C.-C.; Ju, M.-S.
2012-04-01
The main goal of this study was to study the performance of fuzzy logic controllers combined with simplified hybrid amplitude/pulse-width (AM/PW) modulation to regulate muscle force via nerve electrical stimulation. The recruitment curves with AM/PW and AM modulations were constructed for the calf muscles of rabbits. Integrated with the modulation methods, a proportional-integral-derivative (PID) and three fuzzy logic controllers were designed and applied for the electrical stimulation of tibial nerves to control the ankle torque under isometric conditions. The performance of the two modulation methods combined with the four controllers was compared when the ankle was fixed at three positions for both in vivo experiments and model simulations using a nonlinear muscle model. For the animal experiments, AM/PW modulation performed better than AM modulation alone. The fuzzy PI controller performed marginally better and was resistant to external noises, though it tended to have a larger overshoot. The performance of the controllers had a similar trend in the three different joint positions, and the simulation results with the nonlinear model matched the experimental results well. In conclusion, AM/PW modulation improved controller performance, while the contribution of fuzzy logic was only marginal.
Lin, C-C K; Liu, W-C; Chan, C-C; Ju, M-S
2012-04-01
The main goal of this study was to study the performance of fuzzy logic controllers combined with simplified hybrid amplitude/pulse-width (AM/PW) modulation to regulate muscle force via nerve electrical stimulation. The recruitment curves with AM/PW and AM modulations were constructed for the calf muscles of rabbits. Integrated with the modulation methods, a proportional-integral-derivative (PID) and three fuzzy logic controllers were designed and applied for the electrical stimulation of tibial nerves to control the ankle torque under isometric conditions. The performance of the two modulation methods combined with the four controllers was compared when the ankle was fixed at three positions for both in vivo experiments and model simulations using a nonlinear muscle model. For the animal experiments, AM/PW modulation performed better than AM modulation alone. The fuzzy PI controller performed marginally better and was resistant to external noises, though it tended to have a larger overshoot. The performance of the controllers had a similar trend in the three different joint positions, and the simulation results with the nonlinear model matched the experimental results well. In conclusion, AM/PW modulation improved controller performance, while the contribution of fuzzy logic was only marginal. PMID:22422279
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.
A novel amplitude modulated triangular carrier gain linearization technique for SPWM inverter
Directory of Open Access Journals (Sweden)
Ramkumar Subburam
2009-01-01
Full Text Available This paper presents a new method to extend the linearity of the sinusoidal pulse width modulation (SPWM to full range of the pulse dropping region. The proposed amplitude modulated triangular carrier PWM method (AMTCPWM increases the dynamic range of the SPWM control and eliminates the need of nonlinear modulation in the pulse dropping region to reach the square wave boundary. The novel method combines the spectral quality of SPWM with the efficient single-mode linear control. A simple analytical characterization of the exact method is presented and its effectiveness is demonstrated using simulation for the basic single-phase H-bridge inverter circuit. The hardware results of the designed prototype inverter are presented to validate the betterment of the novel scheme. .
Amplitude modulation of hydromagnetic waves and associated rogue waves in magnetoplasmas.
Sabry, R; Moslem, W M; Shukla, P K
2012-09-01
It is shown that the dynamics of amplitude-modulated compressional dispersive Alfvénic (CDA) waves in a collisional megnetoplasma is governed by a complex Ginzburg-Landau (CGL) equation. The nonlinear dispersion relation for the modulational instability of the CDA waves is derived and investigated numerically. It is found that the growth rate of the modulational instability decreases (increases) with the increase of the normalized electron-ion collision frequency ? (the plasma ?). The modulational instability criterion for the CGL equation is defined precisely and investigated numerically. The region of the modulational instability becomes narrower with the increase of ? and ?, indicating that the system dissipates the wave energy by collisions, and a stable CDA wave envelope packet in the form of a hole will be a dominant localized pulse. For a collisionless plasma, i.e., ?=0, the CGL equation reduces to the standard nonlinear Schrödinger (NLS) equation. The latter is used to investigate the modulational (in)stability region for the CDA waves in a collisionless magnetoplasma. It is shown that, within unstable regions, a random set of nonlinearly interacting CDA perturbations leads to the formation of CDA rogue waves. In order to demonstrate that the characteristics of the CDA rogue waves are influenced by the plasma ?, the relevant numerical analysis of the appropriate nonlinear solution of the NLS equation is presented. The application of our investigation to space and laboratory magnetoplasmas is discussed. PMID:23031035
Non-quadrature amplitude modulation: a novel interferometric method for phase retrieval
Rivera-Ortega, Uriel; Meneses-Fabian, Cruz
2015-07-01
Phase-shifting interferometry (PSI) is a well-known technique used to calculate the phase of a resulting wavefront. This wavefront is commonly originated from the superposition of a known reference wavefront with a distorted wavefront, resulting in an interference pattern. In order to extract information about the resulting wavefront (which can be related to surfaces thicknesses, surface roughness, optical power, material homogeneity, temperature, index of refraction, just to mention a few), a set of interference patterns are generally changed in a known phase-step to form a resoluble system of equations. In PSI the contrast, visibility and phase variations of the resulting interference patterns are considered homogeneous and spatially constant, respectively. These conditions are hard to obtain experimentally, even though a carefully calibrated phase shifter and/or optical elements of high quality are used to carry out the experimental setup. In this manuscript, we present a novel and alternative method for phase extraction named phase-visibility modulating interferometry (PVMI), which introduces spatial variations of phase and visibility in the interferogram. The phase is computed from the measured intensities, and thus the interferograms can be normalized and their phase variations can be also known. The spatial variations are introduced by modulating in phase and amplitude a reference beam by non-quadrature amplitude modulation (NQAM), achieved by the sum of two beams out of phase within the range (0, 2Pi) and by the modulation of their amplitudes. NQAM is produced in this proposal by using dark sheets as amplitude filters, neutral density filters and the diffraction orders of a grating, which considerably reduce the expenses generated when using common phase shifter devices such as piezoelectric transducers; besides that the amplitude filters need no calibration. In PVMI the spatial variations of phase and visibility do not represent any problem, however the phase difference between the reference beams has to remain temporally constant, which represent an experimental problem. For this reason, in order to overcome this inconvenient PVMI also has been implemented in a single shot. A theoretical analysis and experimental results will be shown for each implementation. The viability of these proposed experimental setups allows them to be easily replicated and used for researching purposes or for teaching special topics in optics for undergraduate or graduate studies in the field of physics.
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.
Wohlgemuth, Sandra; Vogel, Astrid; Ronacher, Bernhard
2010-01-01
Using modulation transfer functions (MTF), we investigated how sound patterns are processed within the auditory pathway of grasshoppers. Spike rates of auditory receptors and primary-like local neurons did not depend on modulation frequencies while other local and ascending neurons had lowpass, bandpass or bandstop properties. Local neurons exhibited broader dynamic ranges of their rate MTF that extended to higher modulation frequencies than those of most ascending neurons. We found no indica...
Simulation of amplitude-modulated circularly polarized Alfven waves for beta less than one
International Nuclear Information System (INIS)
We study the nonlinear properties of the amplitude-modulated circulary polarized Alfven wave for ?<1. The temporal behavior of the wave packet of the electromagnetic hybrid simulation is compared with a numerical solution of the derivative nonlinear Schroedinger (DNLS) equation. It is shown that the left-hand-polarized mode evolves into a shocklike structure due to the modulational instability. However, both cyclotron damping and a snowplow effect near the steepened wave packet suppress its further steepening, contrary to the predictions of the DNLS equation. For the right-hand mode, formation of the shock does not take place, and the initial time development is well described by the DNLS equation. The daughter Alfven wave and ion acoustic waves are excited due to the decay instability at a later time. Heating or acceleration of the particles takes place for both left- and right-hand waves. Energy transfer from the wave to the particles occurs effectively when substantial modulation in the wave amplitude is present. The significance of this result is briefly discussed. copyright American Geophysical Union 1987
Chow, C W; Talli, G; Ellis, A D; Townsend, P D
2008-02-01
We demonstrate a novel Rayleigh interferometric noise mitigation scheme for applications in carrier-distributed dense wavelength division multiplexed (DWDM) passive optical networks at 10 Gbit/s using carrier suppressed subcarrier-amplitude modulated phase shift keying modulation. The required optical signal to Rayleigh noise ratio is reduced by 12 dB, while achieving excellent tolerance to dispersion, subcarrier frequency and drive amplitude variations. PMID:18542264
International Nuclear Information System (INIS)
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.
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.
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...
International Nuclear Information System (INIS)
The procedure integrating independent amplitude-distance and amplitude-frequency measurements into a single routine with two variables (frequency and distance) has been developed. The domains of attraction and repulsion regimes of probe-surface interactions are clearly identified on two-dimensional patterns in frequency-distance space due to the stepwise change in a slope of constant amplitude lines and their shear on boundaries. Pattern evolution with the driving amplitude variation was studied, and three characteristic pattern types were selected. The topology of patterns obtained at intermediate drivings indicates that the probe-surface interaction is attractive at large and low cantilever-surface separations being repulsive at intermediate separations
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.
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
Influence of stimulus intensity on the soleus H-reflex amplitude and modulation during locomotion
DEFF Research Database (Denmark)
Simonsen, Erik B; Alkjær, Tine
2013-01-01
Diverging results have been reported regarding the modulation and amplitude of the soleus H-reflex measured during human walking and running. A possible explanation to this could be the use of too high stimulus strength in some studies while not in others. During activities like walking and running it is necessary to use a small M-wave to control the effective stimulus strength during all phases of the movement. This implies that the descending part of the H-reflex recruitment curve is being used, which may lead to an unwanted suppression of the H-reflex due to limitations imbedded within the H-reflex methodology itself. Accordingly, the purpose of the present study was to study the effect on the soleus H-reflex during walking and running using stimulus intensities normally considered too high (up to 45% Mmax). Using M-waves of 25-45% Mmax as opposed to 5-25% Mmax showed a significant suppression of the peak H-reflex during the stance phase of walking, while no changes were observed during running. No differences were observed regarding modulation pattern. So a possible use of too high stimulus intensity cannot explain the differences mentioned. The surprising result in running may be explained by the much higher voluntary muscle activity, which implies the existence of a V-wave influencing the H-reflex amplitude in positive direction.
Amplitude modulation depth discrimination in hearing-impaired and normal-hearing listeners
DEFF Research Database (Denmark)
Ewert, Stephan D.; Volmer, Jutta
2008-01-01
The processing of amplitude modulations (AM) of sounds is assumed to be crucial for decoding and understanding of speech in humans. Since hearing-impaired (HI) listeners often suffer from severely hampered speech intelligibility, particularly in reverberant or noisy environments, they might also show degraded performance in AM processing tasks. However, several studies indicated a similar or even better performance in AM detection tasks for sensorineural HI listeners than for normal hearing (NH) listeners when reduced audibility was compensated. In addition to AM detection, this study investigates the differential processing of amplitude modulation depth in HI and NH listeners. AM-depth discrimination of a 4-, 8-, and 30-Hz sinusoidal AM, imposed on a 1- or 4-kHz pure-tone carrier, was measured. The AM of the standard ranged from being well detectable to near threshold. AM-depth discrimination thresholds strongly varied among HI listeners and were elevated in comparison to NH for high standard depths. A model of AM processing is suggested incorporating an individually adjusted simulation of the auditory periphery. To account for the data of HI listeners, however, the key element appeared to be an increased internal noise in the AM-depth domain. Consequences for speech perception are discussed.
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
Travel Time Shifts due to Amplitude Modulation in Time-Distance Helioseismology
Nigam, R
2009-01-01
Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times has not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is 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 wave...
Acousto-optic tomography using amplitude-modulated focused ultrasound and a near-IR laser
International Nuclear Information System (INIS)
A novel tomographic method that can be applied in strongly scattering optical media is proposed. 1-MHz focused ultrasound is used to tag the scattering photons in the biological tissue; it carries a 10-KHz sinusoidal wave to act as a detection wave through amplitude-modulation (AM). The scattering photons that come from the focused zone carry the modulated information. Their optoelectronic signal is demodulated by real-time FFT. By detecting and discriminating ultrasound-modulated information carried by scattered photons, the optical tomographic images of the media simulating biological tissue and of a buried object are reconstructed by the AM spectral intensity. This ultrasound-tagged optical tomography can be applied to tissue structures with different optical parameters. For the first time, by using this method, we obtained the tomographic image of a 5 mm-wide soft rubber cube buried in a biological tissue-simulating media with a detecting depth of 30 mm. (laser applications and other topics in quantum electronics)
Li, Xinying; Yu, Jianjun; Chi, Nan; Zhang, Junwen
2013-11-15
We propose and experimentally demonstrate an optical wireless integration system at the Q-band, in which up to 40 Gb/s polarization multiplexing multilevel quadrature amplitude/phase modulation (PM-QAM) signal can be first transmitted over 20 km single-mode fiber-28 (SMF-28), then delivered over a 2 m 2 × 2 multiple-input multiple-output wireless link, and finally transmitted over another 20 km SMF-28. The PM-QAM modulated wireless millimeter-wave (mm-wave) signal at 40 GHz is generated based on the remote heterodyning technique, and demodulated by the radio-frequency transparent photonic technique based on homodyne coherent detection and baseband digital signal processing. The classic constant modulus algorithm equalization is used at the receiver to realize polarization demultiplexing of the PM-QAM signal. For the first time, to the best of our knowledge, we realize the conversion of the PM-QAM modulated wireless mm-wave signal to the optical signal as well as 20 km fiber transmission of the converted optical signal. PMID:24322113
The effect of amplitude modulation on subharmonic imaging with chirp excitation.
Harput, Sevan; Arif, Muhammad; McLaughlan, James; Cowell, David M J; Freear, Steven
2013-12-01
Subharmonic generation from ultrasound contrast agents depends on the spectral and temporal properties of the excitation signal. The subharmonic response can be improved by using wideband and long-duration signals. However, for sinusoidal tone-burst excitation, the effective bandwidth of the signal is inversely proportional to the signal duration. Linear frequency-modulated (LFM) and nonlinear frequency-modulated (NLFM) chirp excitations allow independent control over the signal bandwidth and duration; therefore, in this study LFM and NLFM signals were used for the insonation of microbubble populations. The amplitude modulation of the excitation waveform was achieved by applying different window functions. A customized window was designed for the NLFM chirp excitation by focusing on reducing the spectral leakage at the subharmonic frequency and increasing the subharmonic generation from microbubbles. Subharmonic scattering from a microbubble population was measured for various excitation signals and window functions. At a peak negative pressure of 600 kPa, the generated subharmonic energy by ultrasound contrast agents was 15.4 dB more for NLFM chirp excitation with 40% fractional bandwidth when compared with tone-burst excitation. For this reason, the NLFM chirp with a customized window was used as an excitation signal to perform subharmonic imaging in an ultrasound flow phantom. Results showed that the NLFM waveform with a customized window improved the subharmonic contrast by 4.35 ± 0.42 dB on average over a Hann-windowed LFM excitation. PMID:24297019
Hermitian $(a, b)$-modules and Saito's "higher residue pairings"
Karwasz, Piotr P.
2011-01-01
Following the work of Daniel Barlet ([Bar97]) and Ridha Belgrade ([Bel01]) the aim of this article is the study of the existence of $(a, b)$-hermitian forms on regular $(a, b)$-modules. We show that every regular $(a,b)$-module with a non-degenerate bilinear form can be written in an unique way as a direct sum of $(a, b)$-modules $E_i$ that admit either an $(a, b)$-hermitian or an $(a, b)$-anti-hermitian form or both; all three cases are equally possible with explicit exampl...
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.
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.
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.
Nishihara, Masato; Kai, Yutaka; Tanaka, Toshiki; Takahara, Tomoo; Li, Lei; Yan, Weizhen; Liu, Bo; Tao, Zhenning; Rasmussen, Jens C.
2013-12-01
Advanced multi-level modulation is an attractive modulation technique for beyond 100 Gbps short reach optical transmission system. Above all, discrete multi-tone (DMT) technique and pulse amplitude modulation (PAM) technique are the strong candidates. We compared the 100 Gbps transmission characteristics of DMT and PAM by simulation and experiment. The comparison was done by using same devices and only the digital signal processing was changed. We studied the transmission distance dependence for 0.5 to 40 km and the impact of the frequency responses of the optical devices. Finally we discuss the features of the both modulation techniques.
Dou, Jiangpei; Ren, Deqing; Zhang, Xi; Zhu, Yongtian; Zhao, Gang; Wu, Zhen; Chen, Rui; Liu, Chengchao; Yang, Feng; Yang, Chao
2014-08-01
Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA) for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose, we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators (SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 ?/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.
Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications
Directory of Open Access Journals (Sweden)
Sethakaset Ubolthip
2005-01-01
Full Text Available We propose a novel differential amplitude pulse-position modulation (DAPPM for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM ? in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR. The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM ? depending on the number of amplitude levels A and the maximum length L of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about 1?dB and 1.5?dB more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM 2 . When the number of bits per symbol is the same, PAM requires more power, and DH-PIM 2 less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.
Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications
Directory of Open Access Journals (Sweden)
Sethakaset Ubolthip
2005-01-01
Full Text Available We propose a novel differential amplitude pulse-position modulation (DAPPM for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR. The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM depending on the number of amplitude levels and the maximum length of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about and more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM . When the number of bits per symbol is the same, PAM requires more power, and DH-PIM less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.
Influence of 100Hz amplitude modulation on the human medial olivocochlear reflex.
Boothalingam, Sriram; Purcell, David; Scollie, Susan
2014-09-19
It is well known that medial olivocochlear system (MOC) activity causes inhibition of cochlear amplification that can be measured using otoacoustic emissions (OAEs). The temporal characteristics of this MOC inhibitory effect are still not well understood. Two experiments were performed to further explore a previously reported enhancement in MOC inhibition of OAEs by a broadband noise (BBN) elicitor modulated at 100Hz (AM-BBN). In experiment I, MOC inhibition was measured for toneburst (1 and 2kHz presented at 41.67Hz) and stimulus-frequency (0.96-1.92kHz) OAEs for two elicitor conditions, BBN and AM-BBN (100% modulation depth [MD]), in 27 young normal hearing adults. In experiment II, tonebursts were presented at 50Hz instead of 41.67Hz to test if the previously reported enhancement of the MOC response to 100Hz AM-BBN is specific to a 50Hz toneburst presentation rate. All elicitors caused significant reduction of both TB- and SF-OAE amplitude. AM-BBN evoked the same OAE inhibition compared to BBN in both experiments. This pattern was consistent across OAE types, and toneburst presentation rates. Results suggest that the MOC is not especially sensitive to 100Hz AM-BBN; instead, AM dips in noise energy likely reduce its effectiveness in evoking MOC activity due to temporal energy integration. PMID:25102324
Amplitude modulation of charge-density-wave domains in 1T-TaS2 at 300 K
International Nuclear Information System (INIS)
Measurements of the charge-density-wave (CDW) amplitude modulation in 1T-TaS2 at room temperature have been made using a scanning tunneling microscope (STM) operating in the constant current mode. The amplitude profiles are in good agreement with the profile predicated by the CDW domain model of Nakanishi and Shiba. Interference effects between the atomic and CDW lattices have been analyzed and do not modify these profiles significantly. They represent the true CDW amplitude variation connected with the CDW domain structure
Hayrapetyan, Armen G; Goette, Joerg B
2015-01-01
We study the impact of spatially homogeneous yet non-stationary PT-symmetric dielectric permittivity in dynamical and spectral properties of light. For such a time-reversal optical system, we analytically construct the instantaneous amplitude and angular frequency of waves within the framework of Maxwell's equations and demonstrate PT modulations of light amplification and attenuation associated with the well-defined regions of gain and loss, respectively. Particularly strong enhancement of amplitude modulation towards the loss domain is shown to be expected depending on fine tuning of parameters of the complex permittivity profile. Moreover, we predict the split of extrema of angular frequency modulation and demonstrate the shrinkage of the modulation period. Our theory can be extended for investigating similar time-dependent effects with matter and acoustic waves in PT-symmetric structures.
Smith, Warren R.
2007-12-01
A formal perturbation scheme is developed to determine original modulation equations for laminar finite-amplitude non-linear waves in an incompressible fluid. Three idealized problems are analysed. The modulation equations comprise conservation of waves, averaged conditions for conservation of mass, momentum, kinetic energy and angular momentum and the averaged projection of the Navier-Stokes equations onto the vorticity vector. The last of these modulation equations, which is related to vortex stretching, only appears in 3D problems. The technique of Reynolds averaging is also employed to obtain equations for the mean velocities and pressure. The Reynolds-averaged Navier-Stokes equations correspond to the modulation equations for conservation of mass and momentum. However, the Reynolds stress transport equations are shown to be inconsistent with the other necessary modulation equations. In two further idealized problems, exact solutions of the Navier-Stokes equations are obtained by employing the modulation equations.
Bibikov, N. G.
2014-09-01
The responses of single neurons of the cochlear nucleus of a grass frog to long tonal signals amplitude-modulated by repeat intervals of low-frequency noise have been studied. The carrier frequency always corresponded to the characteristic frequency of the studied cell (a range of 0.2 kHz-2 kHz); the modulated signal was noise in the ranges 0-15 Hz, 0-50 Hz, or 0-150 Hz. We obtained the correlation functions of the cyclic histogram reflecting the change in probability of a neuron pulse discharge (spike) during the modulation period with the shape of the signal envelope in the same period. The form of the obtained correlation functions usually does not change qualitatively with a change in carrier level or modulation depth; however, this could essentially depend of the frequency component of the modulating function. In the majority of cases, comparison of the cyclic histogram of the reaction with only the current amplitude value does not adequately reveal the signal's time features that determine the reaction of a neuron. The response is also determined by the other sound features, primarily by the rate of the change in amplitude. The studied neurons differed among themselves, both in preference toward a certain range of modulated frequencies and in the features of the envelope that caused the cell's response.
DEFF Research Database (Denmark)
Rodes Lopez, Roberto; Wieckowski, Marcin
2011-01-01
We experimental demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs.
Rodes, Roberto; Wieckowski, Marcin; Pham, Thang Tien; Jensen, Jesper Bevensee; Turkiewicz, Jarek; Siuzdak, Jerzy; Monroy, Idelfonso Tafur
2011-12-19
We experimentally demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs. PMID:22274239
DEFF Research Database (Denmark)
Rodes Lopez, Roberto; Wieckowski, Marcin
2011-01-01
We experimentally demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs. © 2011 Optical Society of America.
Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel
Moore, Jay; Colón, Raul D.; Tadanki, Sasidhar; Waddell, Kevin W.
2014-08-01
The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins (13C and 1H) at 12 mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128 kHz (13C) and 510 kHz (1H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as hardware complexity and bulk, weighed against the caveat that elaborate pulses are required. More work will be necessary to test this method on the targeted application of parahydrogen induced hyperpolarization as well as to quantify efficiency, but upon further development we anticipate that this method may offer a viable ‘software’ approach to heteronuclear manipulations of spins at low magnetic fields.
Amplitude modulation patterns of local field potentials reveal asynchronous neuronal populations.
Díaz, Javier; Razeto-Barry, Pablo; Letelier, Juan-Carlos; Caprio, John; Bacigalupo, Juan
2007-08-22
Neural oscillations, which appear in several areas of the nervous system and cover a wide frequency range, are a prominent issue in current neuroscience. Extracellularly recorded oscillations are generally thought to be a manifestation of a neural population with synchronized electrical activity resulting from coupling mechanisms. The vertebrate olfactory neuroepithelium exhibits beta-band oscillations, termed peripheral waves (PWs), in their population response to odor stimulation. Here, we examine PWs in the channel catfish and propose that their properties could be explained as the superposition of asynchronous oscillators. Our model shows that the intriguing random pattern of amplitude-modulated PWs could be explained by Rayleigh fading, an interference phenomenon well known in physics and recognizable using statistical methods and signal analysis. We are proposing a mathematical fingerprint to characterize neural signals generated by the addition of random phase oscillators. Our interpretation of PWs as arising from asynchronous oscillators could be generalized to other neuronal populations, because it suggests that neural oscillations, detected in local field potential recordings within a narrow frequency band, do not necessarily originate from synchronization events. PMID:17715359
Vieira, Sónia; Ribeiro, Lourenço; Jesus, Bruno; Cartaxana, Paulo; da Silva, Jorge Marques
2013-01-01
Imaging pulse amplitude modulated (Imaging-PAM) fluorometry is a breakthrough in the study of spatial heterogeneity of photosynthetic assemblages. However, Imaging and conventional PAM uses a different technology, making comparisons between these techniques doubtful. Thereby, photosynthetic processes were comparatively assessed using conventional (Junior PAM and PAM 101) and Imaging-PAM on intertidal microphytobenthos (MPB; mud and sand) and on cork oak leaves. Lower values of ? (initial slope of the rETR, relative photosynthetic electron transport rate) vs E (incident photosynthetic active radiation) curve), ETR(max) (maximum relative ETR), E(k) (light saturation parameter) and F(v)/F(m) (maximum quantum efficiency of photosystem II of dark-adapted samples) were obtained using the Imaging-PAM. The level of discrepancy between conventional and Imaging-PAM systems was dependent on the type of sample, being more pronounced for MPB muddy sediments. This may be explained by differences in the depth integration of the fluorescence signal related to the thickness of the photosynthetic layer and in the light attenuation coefficients of downwelling irradiance. An additional relevant parameter is the taxonomic composition of the MPB, as cyanobacteria present in sandy sediments rendered different results with red and blue excitation light fluorometers. These findings emphasize the caution needed when interpreting chlorophyll fluorescence data of MPB communities. PMID:22891982
Enabling practical surface acoustic wave nebulizer drug delivery via amplitude modulation.
Rajapaksa, Anushi; Qi, Aisha; Yeo, Leslie Y; Coppel, Ross; Friend, James R
2014-06-01
A practical, commercially viable microfluidic device relies upon the miniaturization and integration of all its components--including pumps, circuitry, and power supply--onto a chip-based platform. Surface acoustic waves (SAW) have become popular in microfluidic manipulation, in solving the problems of microfluidic manipulation, but practical applications employing SAW still require more power than available via a battery. Introducing amplitude modulation at 0.5-40 kHz in SAW nebulization, which requires the highest energy input levels of all known SAW microfluidic processes, halves the power required to 1.5 W even while including the power in the sidebands, suitable for small lithium ion batteries, and maintains the nebulization rate, size, and size distributions vital to drug inhalation therapeutics. This simple yet effective means to enable an integrated SAW microfluidics device for nebulization exploits the relatively slow hydrodynamics and is furthermore shown to deliver shear-sensitive biomolecules--plasmid DNA and antibodies as exemplars of future pulmonary gene and vaccination therapies--undamaged in the nebulized mist. Altogether, the approach demonstrates a means to offer truly micro-scale microfluidics devices in a handheld, battery powered SAW nebulization device. PMID:24740643
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.
Sethakaset, Ubolthip; Gulliver, T. Aaron
2005-02-01
We investigate the performance of a differential amplitude pulse-position modulation with return-to-zero coding (DAPPM-RZ) over an indoor optical wireless channel. We compare the performance of DAPPM-RZ(A=2) with DAPPM(A=2), DPPM and DH-PIM. The result shows that, over a non-dispersive channel, DAPPM-RZ yields better power efficiency than DAPPM. It requires about 1.5 dB less transmit power. However, the bandwidth of DAPPM-RZ is double that of DAPPM. Compared to DPPM, the bandwidth of DAPPM-RZ is about the same as that of DPPM but DAPPM-RZ yields less power efficiency. When the number of bits/symbol(M) is above 3, the DAPPM-RZ is superior to DH-PIM_2 in terms of power efficiency but has less bandwidth efficiency. Over a dispersive channel, given the same value of M, DAPPM-RZ outperforms DPPM, DAPPM (without RZ) and DH-PIM2 when the normalized rms delay spread is high.
Pasteau, Magali; Ung, Davy; Kreutzer, Michel; Aubin, Thierry
2012-07-01
Song discrimination and recognition in songbird species have usually been studied by measuring responses to song playbacks. In female canaries, Serinus canaria, copulation solicitation displays (CSDs) are used as an index of female preferences, which are related to song recognition. Despite the fact that many studies underline the role of song syntax in this species, we observed that short segments of songs (a few seconds long) are enough for females to discriminate between conspecific and heterospecific songs, whereas such a short duration is not sufficient to identify the syntax rules. This suggests that other cues are salient for song recognition. In this experiment, we investigated the influence of amplitude modulation (AM) on the responses (CSDs) of female canaries to song playbacks. We used two groups of females: (1) raised in acoustic isolation and (2) raised in normal conditions. When adult, we tested their preferences for sexy phrases with different AMs. We broadcast three types of stimuli: (1) songs with natural canary AM, (2) songs with AM removed, or (3) song with wren Troglodytes troglodytes AM. Results indicate that female canaries prefer and have predispositions for a song type with the natural canary AM. Thus, this acoustic parameter is a salient cue for song attractiveness. PMID:22476242
Veselovskaya, T. V.; Klochan, E. L.; Lariontsev, E. G.; Parfenov, S. V.; Shelaev, A. N.
1990-07-01
Theoretical and experimental investigations demonstrated that in real acoustooptic modulators the diffraction of light by a standing ultrasonic wave may give rise to both phase and amplitude nonreciprocities of counterpropagating light waves. Analytic expressions are derived for the dependences of these nonreciprocities on the parameters of the traveling component of an ultrasonic wave in a modulator. It is shown that when the angle of incidence of light on a modulator deviates from the Bragg angle, the phase nonreciprocity may be suppressed, but the amplitude nonreciprocity becomes maximal and its sign is governed by the law of deviation of the angle of incidence from the Bragg angle. A diffraction acoustooptic feedback makes it possible not only to achieve mode locking with an acoustooptic modulator utilizing a traveling ultrasonic wave, but also to control the magnitude and sign of amplitude-frequency nonreciprocities. It is reported that an acoustooptic feedback can be used to generate self-pumping waves in a solid-state mode-locked ring laser and thus stabilize bidirectional lasing in a wide range of the frequency offset between the counterpropagating waves.
Herlory, Olivier; Bonzom, Jean-Marc; Gilbin, Rodolphe
2013-09-15
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 5h 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 ( [Formula: see text] , EC50=303 ± 64 ?g UL(-1) after 5h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC50=142 ± 98 ?g UL(-1) after 5h 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. PMID:23851055
Cui, Sheng; He, Sheng; Shang, Jin; Ke, Changjian; Fu, Songnian; Liu, Deming
2015-06-01
A method to improve the performance of the asynchronous amplitude histogram (AAH) based optical modulation format identification system is proposed. It is demonstrated that with additional static dispersion compensation modules (SDCMs), polarization and non-polarization multiplexed (PM/NPM) signals can be distinguished simply from the AAH peak position difference, while the stringent chromatic dispersion limit imposed on the MFI method can be expanded up to desired values by selectively enabling the SDCMs to minimize the width to area ratio (WAR) of the AAH. Numerical simulations and experiments are carried out to demonstrate the effectiveness of this method.
International Nuclear Information System (INIS)
The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection (DPD) method in the signal waveform modulation multi-level (SWML) read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc. (classical areas of phenomenology)
International Nuclear Information System (INIS)
The effects of amplitude modulation (AM) on an atmospheric pressure microwave argon jet is investigated using time-resolved optical emission spectroscopy, passive acoustic diagnostic and digital camera imaging. These techniques show significant changes of the effluent plasma properties with varying AM frequency. Operation in AM mode can enhance the plasma jet length or width over continuous-wave mode with the same mean power, which could be advantageous in many practical applications of plasma jets. (paper)
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.
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...
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
Hnilica, J.; Kudrle, V.
2014-02-01
The effects of amplitude modulation (AM) on an atmospheric pressure microwave argon jet is investigated using time-resolved optical emission spectroscopy, passive acoustic diagnostic and digital camera imaging. These techniques show significant changes of the effluent plasma properties with varying AM frequency. Operation in AM mode can enhance the plasma jet length or width over continuous-wave mode with the same mean power, which could be advantageous in many practical applications of plasma jets.
International Nuclear Information System (INIS)
Cerebral cortex tissue slices and cerebral hemispheres prepared from Gallus domesticus chicks were exposed to 147 MHz radiofrequency radiation, amplitude modulated at 16 Hz and applied at a power density of 0.75 mW/cm2, to determine the effect of such exposure of 45Ca2+ efflux from the avian brain tissue. Statistical analysis of these data demonstrates that such exposure has no significant effect on 45Ca2+ efflux
Effect of four-wave mixing spatial dependence on idler residual modulation
International Nuclear Information System (INIS)
We investigate the possibilities of controlling and exploiting the spatial evolution of the four-wave mixing (FWM) idler in a fiber optical parametric amplifier, considering standard single-mode fibers. We found that the use of high pump powers, for a given requirement on the signal extinction ratio and frequency separation between pump and signal, can considerably affect the optical signal-to-noise ratio on the idler frequency due to the residual modulation. We observe that by choosing an opportune length of the fiber, the residual idler modulation can be suppressed or counteracted by an increase of optical average power. Thus, a proper choice of the transmission fiber length can considerably improve the remodulated idler characteristics.
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.
The effect of carrier level on tuning in amplitude-modulation maskinga
Wojtczak, Magdalena
2011-01-01
The effect of carrier level on tuning in modulation masking was investigated for noise and tonal carriers. Bandwidths of the modulation filters, estimated from the masked detection thresholds using an envelope power spectrum model, were independent of level for the noise carrier but seemed to decrease with increasing level for the tonal carrier. However, the apparently sharper tuning could be explained by increased modulation sensitivity and modulation dynamic range with increasing level rath...
Non-linear frequency and amplitude modulation of a nano-contact spin torque oscillator
Muduli, P. K.; Pogoryelov, Ye; Bonetti, S.; Consolo, G.; Mancoff, Fred; A?kerman, Johan
2009-01-01
We study the current controlled modulation of a nano-contact spin torque oscillator. Three principally different cases of frequency non-linearity ($d^{2}f/dI^{2}_{dc}$ being zero, positive, and negative) are investigated. Standard non-linear frequency modulation theory is able to accurately describe the frequency shifts during modulation. However, the power of the modulated sidebands only agrees with calculations based on a recent theory of combined non-linear frequency and ...
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
DEFF Research Database (Denmark)
Peucheret, Christophe; Lorenzen, Michael Rodas
2008-01-01
Input power dynamic range enhancement and amplitude regeneration of highly distorted signals are demonstrated experimentally for 40 Gbit/s RZ-DPSK in a single-pump fibre parametric amplifier with 22 dB smallsignal gain.
Jordan, Thomas E.; Baker, Gregory S.; Henn, Keith; Messier, Jean-Pierre
2004-05-01
Amplitude variation with offset analysis of ground penetrating radar data (AVO/GPR) may improve the differentiation of nonaqueous phase liquid (NAPL) from stratigraphic changes. Previous controlled experiments have shown that common offset (CO) GPR methods can detect the presence of NAPL in soil by examining amplitude and travel time (velocity) anomalies. Unfortunately, stratigraphic changes such as the presence of a silt or clay lens or perched water table may produce similar amplitude and velocity anomalies. Therefore, it is difficult to delineate NAPL in a terrain with unknown stratigraphy exclusively using CO data collection methods. Forward models based on the Fresnel equations predict that amplitude responses exist at various incidence angles that will allow for differentiating NAPL from hydrogeologic changes. Models generated as part of this study indicate that analyzing the difference in amplitude responses from linearly polarized electric field vertically oriented ( EV) to the horizontally oriented ( EH) signals at various incidence angles improves target discrimination. A case history is presented demonstrating that collecting common-midpoint (CMP) GPR data using EH and EV polarized signals at anomalous CO amplitude responses and analyzing the data using AVO and normalized residual polarization (NRP) methods may improve the detection and differentiation of NAPL from stratigraphic changes in the subsurface. These results are corroborated using a capacitively coupled resistivity instrument and subsequent intrusive sampling.
Steiner Thomas H; Bürki Alexander; Ferguson Stephen J; Gantenbein-Ritter Benjamin
2012-01-01
Abstract Background It has been demonstrated that frequency modulation of loading influences cellular response and metabolism in 3D tissues such as cartilage, bone and intervertebral disc. However, the mechano-sensitivity of cells in linear tissues such as tendons or ligaments might be more sensitive to changes in strain amplitude than frequency. Here, we hypothesized that tenocytes in situ are mechano-responsive to random amplitude modulation of strain. Methods We compared stochastic amplitu...
International Nuclear Information System (INIS)
Femtosecond coherent anti-Stokes Raman scattering (CARS) spectra suffer from low spectral resolution because of the broadband laser spectrum. In this paper, we propose a feasible scheme to achieve a high-resolution two-pulse CARS spectrum by shaping both the pump and probe pulses using rectangular amplitude modulation. We show that a narrowband hole in the CARS spectrum can be created by the amplitude-shaped laser pulse, the position of which is correlated with the Raman resonant frequency of the molecule. Thus, by observing holes in the CARS spectrum, we are able to obtain a high-resolution CARS spectrum and the energy-level diagram of the molecule. (paper)
International Nuclear Information System (INIS)
Mechanical surface treatments such as deep rolling are known to affect the near-surface microstructure and induce, e.g. residual stresses and/or increase the surface hardness. It is well known that, e.g. compressive residual stress states usually increase the lifetime under fatigue loading. The stress relaxation behaviour and the stability of the residual stress during fatigue loading depend on the mechanical surface treatment method. In this paper three different surface treatments are used and their effects on the low cycle fatigue behaviour of austenitic stainless steel (AISI 304) and ferritic-pearlitic steel (SAE 1045) are investigated. X-ray diffraction is applied for the non-destructive evaluation of the stress state and the microstructure. It is found that consecutive deep rolling and annealing as well as high temperature deep rolling produce more stable near-surface stress states than conventional deep rolling at room temperature. The plastic strain amplitudes during fatigue loading are measured and it is shown that they correlate well with the induced residual stress and its relaxation, respectively. Furthermore, Coffin-Manson plots are presented which clearly show the correlation between the plastic strain amplitude and the fatigue lifetime
International Nuclear Information System (INIS)
This paper investigates the phenomenon of stochastic resonance in a single-mode laser driven by quadratic pump noise and amplitude-modulated signal. A new linear approximation approach is advanced to calculate the signal-to-noise ratio. In the linear approximation only the drift term is linearized, the multiplicative noise term is unchangeable. It is found that there appears not only the standard form of stochastic resonance but also the broad sense of stochastic resonance, especially stochastic multiresonance appears in the curve of signal-to-noise ratio as a function of coupling strength ? between the real and imaginary parts of the pump noise. (general)
Characterization of InGaAs self-mixing detectors for chirp amplitude-modulated ladar (CAML)
Aliberti, Keith; Ruff, William C.; Shen, Hongen; Newman, Peter G.; Giza, Mark M.; Sarney, Wendy; Stead, Michael R.; Dammann, John; Mehandru, Rishabh; Ren, Fan
2004-09-01
The U.S. Army Research Laboratory (ARL) has developed a number of near-infrared, prototype laser detection and ranging (LADAR) Systems based on the chirp, amplitude-modulated LADAR (CAML) architecture. The use of self-mixing detectors in the receiver, that have the ability to internally detect and down-convert modulated optical signals, have significantly simplified the LADAR design. Recently, ARL has designed and fabricated single-pixel, self-mixing, InGaAs-based, metal-semiconductor-metal detectors to extend the LADAR operating wavelength to 1.55 mm and is currently in the process of designing linear arrays of such detectors. This paper presents fundamental detector characterization measurements of the new 1.55 mm detectors in the CAML architecture and some insights on the design of 1.55 ?m linear arrays.
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.
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.
Line shape of amplitude or frequency-modulated spectral profiles including resonator distortions.
Suter, Martin; Quack, Martin
2015-05-10
We report experiments and an improved method of analysis for any harmonics of frequency-modulated spectral line shapes allowing for very precise determinations of the resonance frequency of single absorption lines for gigahertz spectroscopy in the gas phase. Resonator perturbations are implemented into the formalism of modulation spectroscopy by means of a full complex transmission function being able to model the asymmetrically distorted absorption line shapes for arbitrary modulation depths, modulation frequencies, and resonator reflectivities. Exact equations of the in-phase and the quadrature modulation signal, taking into account a full resonator transmission function, are simultaneously adjusted to two-channel lock-in measurements performed in the gigahertz regime to obtain the spectral line position. The determination of the absorption line position of the rotational transition J'=7?J''=6 of O16C12S32 in the vibrational ground state is investigated while changing the resonator distortions. The results are subjected to the approach proposed here and compared to standard methods known from the literature. PMID:25967497
Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew
2015-03-01
Tissue stiffness can be measured from the propagation speed of shear waves. Acoustic radiation force (ARF) can generate shear waves by focusing ultrasound in tissue for ~100 ?s. Safety considerations and electronics abilities limit ultrasound pressures. We previously presented shear wave elastography combining ARF and phase-sensitive optical coherence tomography (PhS-OCT) [1]. Here, we use amplitude-modulated ARF to enhance shear wave signal-to-noise ratio (SNR) at low pressures. Experiments were performed on tissue-mimicking phantoms. ARF was applied using a single-element transducer, driven by a 7.5 MHz, 3-ms, sine wave modulated in amplitude by a linear-swept frequency (1 to 7 kHz). Pressures between 1 to 3 MPa were tested. Displacements were tracked using PhS-OCT and numerically compressed using pulse compression methods detailed in previous work [2]. SNR was compared to that of 200-?s bursts. Stiffness maps were reconstructed using time-of-flight computations. 200-?s bursts give barely detectable displacements at 1 MPa (3.7 dB SNR). Pulse compression gives 36.2 dB at 1.5 MPa. In all cases with detectable displacements, shear wave speeds were determined in 5%-gelatin and 10%-gelatin phantoms and compared to literature values. Applicability to ocular tissues (cornea, intraocular lens) is under investigation.
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.
Travel Time Shifts due to Amplitude Modulation in Time-Distance Helioseismology
Nigam, R.; Kosovichev, A. G.
2009-01-01
Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times has not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is ar...
DEFF Research Database (Denmark)
Isaeva, Olga B.; Kuznetsov, Sergey P.
2011-01-01
The paper proposes an approach to constructing feasible examples of dynamical systems with hyperbolic chaotic attractors based on the successive transfer of excitation between two pairs of self-oscillators that are alternately active. An angular variable that measures the relations of the current amplitudes for the two oscillators of each pair undergoes a transformation in accordance with the expanding circle map during each cycle of the process. We start with equations describing the dynamics in terms of complex or real amplitudes and then examine two models based on van der Pol oscillators. One model corresponds to the situation of equality of natural frequencies of the partial oscillators, and another to a nonresonant ratio of the oscillation frequencies relating to each of the two pairs. Dynamics of all models are illustrated with diagrams indicating the transformation of the angular variables, portraits of attractors, Lyapunov exponents, etc. The uniformly hyperbolic nature of the attractor in the stroboscopic Poincare map is confirmed for a real-amplitude version of the equations by computations of statistical distribution of angles between stable and unstable manifolds at a representative set of points on the attractor. In other versions of the equations the attractors relate presumably to the partially hyperbolic class.
Low-bias terahertz amplitude modulator based on split-ring resonators and graphene.
Degl'Innocenti, Riccardo; Jessop, David S; Shah, Yash D; Sibik, Juraj; Zeitler, J Axel; Kidambi, Piran R; Hofmann, Stephan; Beere, Harvey E; Ritchie, David A
2014-03-25
Split-ring resonators represent the ideal route to achieve optical control of the incident light at THz frequencies. These subwavelength metamaterial elements exhibit broad resonances that can be easily tuned lithographically. We have realized a design based on the interplay between the resonances of metallic split rings and the electronic properties of monolayer graphene integrated in a single device. By varying the major carrier concentration of graphene, an active modulation of the optical intensity was achieved in the frequency range between 2.2 and 3.1 THz, achieving a maximum modulation depth of 18%, with a bias as low as 0.5 V. PMID:24558983
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.
Laser-amplitude-modulated dual photopyroelectric/optical-transmittance hydrogen sensor
Garcia, Jose A.; Mandelis, A.
1999-03-01
A dual photopyroelectric/optical-transmittance (PPE/OT) hydrogen sensor has been demonstrated. The sensor consists of a PVDF film sandwiched by two Pd thin-film elements and operates on the principle of frequency modulated laser-intensity. The detection range of this sensor is between 0.5%-100% [H2] by volume in N2. This sensor is very durable and robust. No palladium delamination or blistering occurs even after repeated exposures to pure hydrogen.
Rhythmic control of mRNA stability modulates circadian amplitude of mouse Period3 mRNA.
Kim, Sung-Hoon; Lee, Kyung-Ha; Kim, Do-Yeon; Kwak, Eunyee; Kim, Seunghwan; Kim, Kyong-Tai
2015-03-01
The daily oscillations observed in most living organisms are endogenously generated with a period of 24 h, and the underlying structure of periodic oscillation is an autoregulatory transcription-translation feedback loop. The mechanisms of untranslated region (UTR)-mediated post-transcriptional regulation (e.g., mRNA degradation and internal ribosomal entry site (IRES)-mediated translation) have been suggested to fine-tune the expression of clock genes. Mouse Period3 (mPer3) is one of the paralogs of Period gene and its function is important in peripheral clocks and sleep physiology. mPer3 mRNA displays a circadian oscillation as well as a circadian phase-dependent stability, while the stability regulators still remain unknown. In this study, we identify three proteins - heterogeneous nuclear ribonucleoprotein (hnRNP) K, polypyrimidine tract-binding protein (PTB), and hnRNP D - that bind to mPer3 mRNA 3'-UTR. We show that hnRNP K is a stabilizer that increases the amplitude of circadian mPer3 mRNA oscillation and hnRNP D is a destabilizer that decreases it, while PTB exhibits no effect on mPer3 mRNA expression. Our experiments describe their cytoplasmic roles for the mRNA stability regulation and the circadian amplitude formation. Moreover, our mathematical model suggests a mechanism through which post-transcriptional mRNA stability modulation provides not only the flexibility of oscillation amplitude, but also the robustness of the period and the phase for circadian mPer3 expression. Mouse Period3 (mPer3) is one of well-known clock genes. We identified three 3'-UTR-binding proteins that modulate the mRNA stability, and they influenced to the amplitude of circadian mPer3 mRNA oscillation. Our mathematical model not only showed the relationship between mRNA stability and its oscillation profile but provided the molecular mechanism for the robustness of the period and the phase in circadian oscillation. hnK, heterogeneous nuclear ribonucleoprotein (hnRNP) K; hnD, hnRNP D; PTB, polypyrimidine tract-binding protein. PMID:25581122
Information retrieval from amplitude modulated fringe patterns using single frame processing methods
Patorski, Krzysztof; Pokorski, Krzysztof; Wielgus, Maciej
2012-01-01
Two single-image methods designed for a fringe image modulation extraction are described. They are based on the two dimensional continuous wavelet transformation (2D CWT) and two dimensional Hilbert transform (2D HT) aided by bidimensional empirical mode decomposition (BEMD). Optimization of the proposed methods is described. Numerical simulations designed to test their performance are presented. Both approaches applicability is verified by processing experimental resonance vibration patterns acquired using time-average interferometry. Obtained results agree well with ones obtained using temporal phase shifting method.
Directory of Open Access Journals (Sweden)
Mouna Karmani
2012-05-01
Full Text Available This paper presents a low-voltage, low-power and fault-tolerant implementation of Double Sideband Suppressed Carrier (DSB-SC amplitude modulator-demodulator circuit for portable communication systems. Through the approximation proposed in this work, a CMOS four quadrant multiplier is used as a (demodulator circuit to generate DSB-SC (demodulated signals. Furthermore, the proposed fault-tolerant modem can be used to enhance the reliability of safety-critical communication systems since it is able to provide duplicated output using two path output computations. The proposed circuit occupies a small surface area and is functional at high frequencies even with a low supply voltage. SPICE simulations of the post-layout extracted CMOS multiplier in a full-custom 32 nm CMOS technology, which include all parasitic, are used to demonstrate the electrical behavior of the circuit.
Mari, Jean; Hibbs, Kathryn; Stride, Eleanor; Eckersley, Robert; Tang, Meng
2010-04-01
Microbubble ultrasound contrast agents allow blood perfusion to be imaged at the cost of an increased attenuation that is not properly handled by existing time gain compensation methods. An automatic TGC has been developed that is able to account for different microbubble concentrations. The technique is an extension of a previously tested approach for modeling the nonlinear dependence of microbubble backscattering upon insonating pressure. The proposed method involves modeling in amplitude of the nonlinear attenuation for both forward and backward propagation, and the solution is achieved through an approximation set to overestimate the attenuation. The resulting equations are used to model and compensate amplitude modulation (AM) images; they are tested on radiofrequency data acquired using a clinical scanner from a gelatin tissue-mimicking phantom submerged in a contrast agent solution in the 0.08 MI to 0.51 MI range at 2 MHz. The nonlinear estimation equation presented here provides a significantly improved amplification profile compared with standard TGC algorithms, resulting in more accurate attenuation correction of the AM image. PMID:20378445
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.
Noisy galvanic vestibular stimulation modulates the amplitude of EEG synchrony patterns.
Kim, Diana J; Yogendrakumar, Vignan; Chiang, Joyce; Ty, Edna; Wang, Z Jane; McKeown, Martin J
2013-01-01
Noisy galvanic vestibular stimulation has been associated with numerous cognitive and behavioural effects, such as enhancement of visual memory in healthy individuals, improvement of visual deficits in stroke patients, as well as possibly improvement of motor function in Parkinson's disease; yet, the mechanism of action is unclear. Since Parkinson's and other neuropsychiatric diseases are characterized by maladaptive dynamics of brain rhythms, we investigated whether noisy galvanic vestibular stimulation was associated with measurable changes in EEG oscillatory rhythms within theta (4-7.5 Hz), low alpha (8-10 Hz), high alpha (10.5-12 Hz), beta (13-30 Hz) and gamma (31-50 Hz) bands. We recorded the EEG while simultaneously delivering noisy bilateral, bipolar stimulation at varying intensities of imperceptible currents - at 10, 26, 42, 58, 74 and 90% of sensory threshold - to ten neurologically healthy subjects. Using standard spectral analysis, we investigated the transient aftereffects of noisy stimulation on rhythms. Subsequently, using robust artifact rejection techniques and the Least Absolute Shrinkage Selection Operator regression and cross-validation, we assessed the combinations of channels and power spectral features within each EEG frequency band that were linearly related with stimulus intensity. We show that noisy galvanic vestibular stimulation predominantly leads to a mild suppression of gamma power in lateral regions immediately after stimulation, followed by delayed increase in beta and gamma power in frontal regions approximately 20-25 s after stimulation ceased. Ongoing changes in the power of each oscillatory band throughout frontal, central/parietal, occipital and bilateral electrodes predicted the intensity of galvanic vestibular stimulation in a stimulus-dependent manner, demonstrating linear effects of stimulation on brain rhythms. We propose that modulation of neural oscillations is a potential mechanism for the previously-described cognitive and motor effects of vestibular stimulation, and noisy galvanic vestibular stimulation may provide an additional non-invasive means for neuromodulation of functional brain networks. PMID:23874865
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
Mutation of outer-shell residues modulates metal ion co-ordination strength in a metalloenzyme.
Foo, Jee-Loon; Jackson, Colin J; Carr, Paul D; Kim, Hye-Kyung; Schenk, Gerhard; Gahan, Lawrence R; Ollis, David L
2010-07-15
The metal ion co-ordination sites of many metalloproteins have been characterized by a variety of spectroscopic techniques and small-molecule model systems, revealing many important insights into the structural determinants of metal ion co-ordination. However, our understanding of this fundamentally and practically important phenomenon remains frustratingly simplistic; in many proteins it is essentially impossible to predict metal ion specificity and the effects of remote 'outer-shell' residues on metal ion co-ordination strength are also poorly defined. This is exemplified by our inability to explain why metalloenzymes with identical metal ion co-ordination spheres, such as the closely related orthologues of bacterial PTE (phosphotriesterase) from Agrobacterium radiobacter and Pseudomonas diminuta, display different metal ion specificity and co-ordination strength. In the present study, we present a series of PTE variants that all possess identical metal ion co-ordination spheres, yet display large differences in their metal ion co-ordination strength. Using measurement of the rates of metal ion dissociation from the active site alongside analysis of structural data obtained through X-ray crystallography, we show that 'outer-shell' residues provide essential support for the metal ion ligands, in effect buttressing them in their optimal orientation. Remote mutations appear to modulate metal ion interactions by increasing or decreasing the stabilizing effects of these networks. The present study therefore provides a description of how the greater protein fold can be modified to 'tune' the strength of metal ion co-ordination and metal ion specificity, as well as reinforcing the concept of proteins as ensembles of conformational states with unique structures and biochemical properties. PMID:20459397
Wydro, Marc J; Warr, Gregory G; Atkin, Rob
2015-05-19
Amplitude-modulated atomic force microscopy (AM-AFM) has been used to study the nanostructure of cetylpyridinium chloride (CPCl)-hexanol-0.2 M NaCl sponge (L3) and lamellar (L?) phases near a mica surface. For both phases, membrane volume fractions of 22, 27, and 32 vol % were investigated, with the L3 or L? phase selected by adjusting the co-surfactant/surfactant ratio (hexanol/CPCl). For the L3 phase, the presence of the surface flattens the three-dimensional bulk structure. AM-AFM clearly resolves the membrane and solvent passages in the near surface layer. Increasing the membrane volume fraction decreases the size of the image features because of the lower solvent content. Within error, the average passage sizes in the near surface layer are the same as those in the bulk at the same concentration. Images of the L? phase reveal undulating near surface sheets. At the highest membrane concentration, the image is very smooth, because the lamellar sheet is confined between the surface and the next near surface layer, which is in close proximity as a result of the low solvent content. As the membrane concentration is reduced, the space between layers is increased and undulations appear in the near surface lamellar structure. Undulations are more pronounced at the lowest membrane volume fraction. PMID:25906083
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.
Directory of Open Access Journals (Sweden)
Steiner Thomas H
2012-11-01
Full Text Available Abstract Background It has been demonstrated that frequency modulation of loading influences cellular response and metabolism in 3D tissues such as cartilage, bone and intervertebral disc. However, the mechano-sensitivity of cells in linear tissues such as tendons or ligaments might be more sensitive to changes in strain amplitude than frequency. Here, we hypothesized that tenocytes in situ are mechano-responsive to random amplitude modulation of strain. Methods We compared stochastic amplitude-modulated versus sinusoidal cyclic stretching. Rabbit tendon were kept in tissue-culture medium for twelve days and were loaded for 1h/day for six of the total twelve culture days. The tendons were randomly subjected to one of three different loading regimes: i stochastic (2 – 7% random strain amplitudes, ii cyclic_RMS (2–4.42% strain and iii cyclic_high (2 - 7% strain, all at 1 Hz and for 3,600 cycles, and one unloaded control. Results At the end of the culture period, the stiffness of the “stochastic” group was significantly lower than that of the cyclic_RMS and cyclic_high groups (both, p Conclusions We conclude that, despite an equivalent metabolic response, stochastically stretched tendons suffer most likely from increased mechanical microdamage, relative to cyclically loaded ones, which is relevant for tendon regeneration therapies in clinical practice.
ENDO, Akira; Iye, Yasuhiro
2005-01-01
The amplitude V_0 of unidirectional periodic potential modulation introduced by a surface grating into a two-dimensional electron gas (2DEG) formed at AlGaAs/GaAs heterointerface is measured as a function of electron density n_e by analyzing commensurability oscillation of the magnetoresistance. The electron density is varied either by applying a bias to a metallic back gate or by illumination. The amplitude decreases with increasing density, with the rate |dV_0/dn_e| roughl...
Factorization of Mellin amplitudes
Gonçalves, Vasco; Trevisani, Emilio
2014-01-01
We introduce Mellin amplitudes for correlation functions of $k$ scalar operators and one operator with spin in conformal field theories (CFT) in general dimension. We show that Mellin amplitudes for scalar operators have simple poles with residues that factorize in terms of lower point Mellin amplitudes, similarly to what happens for scattering amplitudes in flat space. Finally, we study the flat space limit of Anti-de Sitter (AdS) space, in the context of the AdS/CFT correspondence, and generalize a formula relating CFT Mellin amplitudes to scattering amplitudes of the bulk theory, including particles with spin.
Correction of the distortion in frequency-modulation spectroscopy
Du Burck, Fre?de?ric; Lopez, Olivier
2004-01-01
A theoretical expression of the detected signal in frequency modulation spectroscopy with a residual amplitude modulation (RAM) is computed. The line shape distortion induced by the RAM is shown to be essentially suppressed for a proper choice of the modulation and detection parameters. The experimental tests are carried out in saturation spectroscopy of I2 at 514.5 nm. Experimental limitations are analysed.
Bräuniger, Thomas; Hempel, Günter; Madhu, P. K.
2006-07-01
In solid-state NMR of quadrupolar nuclei with half-integer spin I, fast amplitude-modulated (FAM) pulse trains have been utilised to enhance the intensity of the central-transition signal, by transferring spin population from the satellite transitions. In this paper, the signal-enhancement performance of the recently introduced SW-FAM pulse train with swept modulation frequency [T. Bräuniger, K. Ramaswamy, P.K. Madhu, Enhancement of the central-transition signal in static and magic-angle-spinning NMR of quadrupolar nuclei by frequency-swept fast amplitude-modulated pulses, Chem. Phys. Lett. 383 (2004) 403-410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW (1/?)-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SW (?)-FAM). For static spectra of 27Al (I = 5/2), better signal-enhancement performance is found for the SW (1/?)-FAM sequence, as demonstrated both by experiments and numerical simulations.
Zargarian, Loussiné; Tisné, Carine; Barraud, Pierre; Xu, Xiaoqian; Morellet, Nelly; René, Brigitte; Mély, Yves; Fossé, Philippe; Mauffret, Olivier
2014-01-01
The HIV-1 nucleocapsid protein (NC) is a small basic protein containing two zinc fingers (ZF) separated by a short linker. It is involved in several steps of the replication cycle and acts as a nucleic acid chaperone protein in facilitating nucleic acid strand transfers occurring during reverse transcription. Recent analysis of three-dimensional structures of NC-nucleic acids complexes established a new property: the unpaired guanines targeted by NC are more often inserted in the C-terminal zinc finger (ZF2) than in the N-terminal zinc finger (ZF1). Although previous NMR dynamic studies were performed with NC, the dynamic behavior of the linker residues connecting the two ZF domains remains unclear. This prompted us to investigate the dynamic behavior of the linker residues. Here, we collected 15N NMR relaxation data and used for the first time data at several fields to probe the protein dynamics. The analysis at two fields allows us to detect a slow motion occurring between the two domains around a hinge located in the linker at the G35 position. However, the amplitude of motion appears limited in our conditions. In addition, we showed that the neighboring linker residues R29, A30, P31, R32, K33 displayed restricted motion and numerous contacts with residues of ZF1. Our results are fully consistent with a model in which the ZF1-linker contacts prevent the ZF1 domain to interact with unpaired guanines, whereas the ZF2 domain is more accessible and competent to interact with unpaired guanines. In contrast, ZF1 with its large hydrophobic plateau is able to destabilize the double-stranded regions adjacent to the guanines bound by ZF2. The linker residues and the internal dynamics of NC regulate therefore the different functions of the two zinc fingers that are required for an optimal chaperone activity. PMID:25029439
McCreery, Douglas; Han, Martin; Pikov, Victor; Yadav, Kamal; Pannu, Satinderpall
2013-10-01
Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This ‘constant maximum’ protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of ABIs may benefit from using pulse rates greater than those presently used in most ABIs, and by sound processing strategies that enhance the modulation depth of the electrical stimulus while preserving dynamic range.
Batshon, Hussam G; Djordjevic, Ivan; Xu, Lei; Wang, Ting
2010-06-21
In this paper, we present a modified coded hybrid subcarrier/ amplitude/phase/polarization (H-SAPP) modulation scheme as a technique capable of achieving beyond 400 Gb/s single-channel transmission over optical channels. The modified H-SAPP scheme profits from the available resources in addition to geometry to increase the bandwidth efficiency of the transmission system, and so increases the aggregate rate of the system. In this report we present the modified H-SAPP scheme and focus on an example that allows 11 bits/Symbol that can achieve 440 Gb/s transmission using components of 50 Giga Symbol/s (GS/s). PMID:20588543
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)
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
Price, Kerry L; Lummis, Sarah C R
2014-10-18
GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using two electrode voltage clamp electrophysiology we show that one substitution (T6'M) ablates picrotoxin inhibition and increases the potency of GABA. This mutation also alters the effect of thymol, which enhances both insect and mammalian GABA responses, and is widely used as a miticide. Thymol decreases the GABA EC50 of WT receptors, enhancing responses, but in T6'M-containing receptors it is inhibitory. The other 3 atypical residues have no major effects on either the GABA EC50, the picrotoxin potency or the effect of thymol. In conclusion we show that the RDL 6' residue is important for channel block, activation and modulation, and understanding its function also has the potential to prove useful in the design of Varroa-specific insecticidal agents. PMID:25460510
Korman Maria; Hoffmann Pablo; Bouchigny Sylvain; Teodorescu Kinneret
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 ...
Hydrophilic Aromatic Residue and in silico Structure for Carbohydrate Binding Module
Chou, Wei-Yao; Pai, Tun-Wen; Jiang, Ting-Ying; Chou, Wei-I; Tang, Chuan-Yi; Margaret Dah-Tsyr CHANG
2011-01-01
Carbohydrate binding modules (CBMs) are found in polysaccharide-targeting enzymes and increase catalytic efficiency. Because only a relatively small number of CBM structures have been solved, computational modeling represents an alternative approach in conjunction with experimental assessment of CBM functionality and ligand-binding properties. An accurate target-template sequence alignment is the crucial step during homology modeling. However, low sequence identities between target/template s...
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.
Vasquez, Bernard J.; Cargill, Peter J.
1993-01-01
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 (about 30 percent) 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 approaches 4. For Beta equal to or greater than 1 and Ti/Te of about 1, the coupled waveforms correspond qualitatively to kinetic treatments of the derivative nonlinear Schroedinger equation.
Residues at the indole-NH of LE300 modulate affinities and selectivities for dopamine receptors.
Robaa, Dina; Kretschmer, Robert; Siol, Oliver; Abulazm, Shams Eldin; Elkhawass, Elsayeda; Lehmann, Jochen; Enzensperger, Christoph
2011-01-01
To further investigate SAR in the class of azecine-type dopamine receptor antagonists, we synthesized a series of derivatives, substituted at the indole-NH of the lead compound LE300 by different alkyl chains in addition to phenylpropyl, allyl, propargyl, and acetyl residues. The affinities of the target compounds for all human dopamine receptors (D(1) -D(5) ) were investigated by radioligand binding assay and their functionality by a calcium assay. Both the affinities and selectivities for the dopamine receptors were found to be affected by the nature of the substituent. The N14-methylated derivative displayed the highest affinities for all D-receptors. In general, the affinities decreased with increasing chain length of the N-alkyl. Different substituents, partly led to altered affinity, and selectivity profile when compared with our lead LE300. PMID:21213349
Bräuniger, Thomas; Madhu, P. K.
2008-07-01
We here investigate the sensitivity enhancement of central-transition NMR spectra of quadrupolar nuclei with spin-7/2 in the solid state, generated by fast amplitude-modulated RF pulse trains with constant (FAM-I) and incremented pulse durations (SW-FAM). Considerable intensity is gained for the central-transition resonance of single-quantum spectra by means of spin population transfer from the satellite transitions, both under static and magic-angle-spinning (MAS) conditions. It is also shown that incorporation of a SW-FAM train into the excitation part of a 7QMAS sequence improves the efficiency of 7Q coherence generation, resulting in improved signal-to-noise ratio. The application of FAM-type pulse trains may thus facilitate faster spectra acquisition of spin-7/2 systems.
Tang, Jin; He, Jing; Xiao, Jiangnan; Chen, Lin
2014-05-01
A kind of blind polarization demultiplexing algorithm based on low-complexity and fast-converging independent component analysis (ICA) for quadrature amplitude modulation (QAM) coherent optical communications systems is proposed. The polarization demultiplexing is achieved by maximizing the signal's non-Gaussianity measured by the information theoretic quantity of negentropy. We demonstrate that some approximate nonlinear functions can be substituted for the negentropy and this greatly reduces the computational complexity. An adaptive gradient optimization algorithm and a fast-converging quasi-Newton algorithm are employed to maximize the negentropy. The numerical simulation and experimental results for polarization division multiplexing quadrature phase shift keying/16QAM without neglecting polarization mode dispersion reveal that the proposed ICA demultiplexing algorithms are feasible and effective for coherent optical receivers.
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.
Karunakaran, Chandra P; Oelze, Michael L
2013-09-01
During application of high intensity focused ultrasound (HIFU) with therapy arrays, the existence of grating lobes can cause heating at unintended tissue regions. Therefore, the reduction of grating lobes in therapeutic arrays is an important goal. One way to reduce the grating lobes in therapy arrays is to excite the arrays with broadband signals (defined here as >10% fractional bandwidth). To achieve a reduction in grating lobe levels in an ultrasonic array, coded waveforms can be utilized that reduce the grating lobe levels while maintaining the spatial peak temporal average intensity. In this study, a 5-MHz, 9-element, 1.25 mm inter-elemental spacing linear array was excited by a sinusoidal waveform, a conventional linear chirp, and a modified linear chirp. Both chirps spanned the -3-dB bandwidth of the transducer. The conventional chirp was a broadband signal with a linear sweep of frequencies between 2.5 and 7.5 MHz, with all frequency components excited with equal amplitude. The modified chirp signal also swept the frequencies between 2.5 and 7.5 MHz, but the amplitude was weighted such that the edges (low and high frequencies of the band) were excited with more energy than the center of the band. In simulations, the field patterns for the sinusoidal, conventional chirp and modified chirp excitations were produced from the array using Field II and compared. For experiments, the beam pattern from a 5-MHz single-element transducer was mapped using a hydrophone for the sinusoidal, conventional chirp and modified chirp excitation. Each field from the transducer was repeated and summed to produce a field from an array of 9 elements. The difference in the time averaged intensity (in dB) in the main lobe and grating lobes were estimated for each excitation and compared. The results demonstrated that the chirp signals resulted in decreases in grating lobe levels compared to the main lobe, i.e. 10 dB down for focusing and 6 dB down for focusing and steering. A further 1 dB decrease in grating lobe levels was observed for the modified chirp excitation compared to the conventional chirp excitation, which corresponds to ~21% reduction in energy deposition at the grating lobe location. PMID:23648212
International Nuclear Information System (INIS)
We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.
Zhang, Jie-Fang; Meng, Jianping; Wu, Lei; Malomed, Boris A
2010-01-01
We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices. By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite number of exact soliton solutions in terms of the Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite bandgap of the optical-lattice-induced spectrum. Starting from the exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.
International Nuclear Information System (INIS)
To determine whether residual interfraction seminal vesicle (SV) displacement necessitates specific planning target volume (PTV) margins during fiducial-guided intensity modulated radiation therapy (IMRT) of the prostate. A planning computed tomography (CT) scan and 2 subsequent CT scans were prospectively obtained for 20 prostate cancer patients with intraprostatic fiducial markers. After CT registration, SV displacement relative to the prostate was quantified as a function of margin size for both the proximal (1 cm) SV (PSV) and the full SV (FSV). Two IMRT plans were simulated for each patient (prostate + PSV and prostate + FSV) both with a uniform 5-mm PTV margin. Minimum clinical target volume (CTV) dose (Dmin) and the volume of SV receiving 95% of the prescription dose (V95%) were assessed during treatment and compared with the initial plan. In all cases, SV displacement with respect to the prostate was greater for the FSV compared with the PSV. To ensure at least 95% geometrical coverage of the CTV for 90% of patients, margins of 5 and 8 mm were required for the PSV and FSV, respectively. Dosimetrically, residual SV displacement had minimal impact on PSV coverage compared with FSV coverage. For the PSV Dmin was ?95% of the prescribed dose in 90% of patients with an overall mean V95% of 99.6 ± 0.8%; for the FSV Dmin was ?95% of the prescribed dose in only 45% of patients with a mean V95% of 97nts with a mean V95% of 97.9 ± 2.4%. The SVs move differentially from the prostate and exhibit greater variation with increasing distance from the prostate. For plans targeting just the prostate and PSVs, 5-mm PTV expansions are adequate. However, despite daily localization of the prostate, larger PTV margins are required for cases where the intent is to completely cover the FSV.
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
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
Energy Technology Data Exchange (ETDEWEB)
Su, Xiaoyun; Agarwal, Vinayak; Dodd, Dylan; Bae, Brian; Mackie, Roderick I.; Nair, Satish K.; Cann, Isaac K.O. (UIUC)
2010-11-22
Carbohydrate binding modules (CBMs) are specialized proteins that bind to polysaccharides and oligosaccharides. Caldanaerobius polysaccharolyticus Man5ACBM16-1/CBM16-2 bind to glucose-, mannose-, and glucose/mannose-configured substrates. The crystal structures of the two proteins represent the only examples in CBM family 16, and studies that evaluate the roles of amino acid residues in ligand binding in this family are lacking. In this study, we probed the roles of amino acids (selected based on CBM16-1/ligand co-crystal structures) on substrate binding. Two tryptophan (Trp-20 and Trp-125) and two glutamine (Gln-81 and Gln-93) residues are shown to be critical in ligand binding. Additionally, several polar residues that flank the critical residues also contribute to ligand binding. The CBM16-1 Q121E mutation increased affinity for all substrates tested, whereas the Q21G and N97R mutants exhibited decreased substrate affinity. We solved CBM/substrate co-crystal structures to elucidate the molecular basis of the increased substrate binding by CBM16-1 Q121E. The Gln-121, Gln-21, and Asn-97 residues can be manipulated to fine-tune ligand binding by the Man5A CBMs. Surprisingly, none of the eight residues investigated was absolutely conserved in CBM family 16. Thus, the critical residues in the Man5A CBMs are either not essential for substrate binding in the other members of this family or the two CBMs are evolutionarily distinct from the members available in the current protein database. Man5A is dependent on its CBMs for robust activity, and insights from this study should serve to enhance our understanding of the interdependence of its catalytic and substrate binding modules.
Phase and amplitude stabilization of superconducting resonators
International Nuclear Information System (INIS)
The problem of phase and amplitude stabilization of the fields in superconducting resonators is described. The problem arises from the fast (approx. 50 Hz) resonator eigenfrequency modulation of magnitude (approx. 100 Hz) which is much larger than the resonator bandwidth (approx. 10 Hz). The problem is compounded by the fact that the coupling between the electrical and mechanical modes of the resonator can lead to instabilities (ponderomotive instabilities). The solution suggested involves operating the resonators in self-excited loops, and electronically modifying the loop parameters in order to lock the loop oscillations to an external phase and amplitude reference without attempt to modify the instantaneous resonator eigenfrequency. It is found that this method of phase stabilization is well suited to resonators with small energy contents and small eigenfrequency deviations since the power required is equal to their product; this occurs when the loaded bandwidth of the resonator is twice the maximum eigenfrequency deviation to be compensated for. It is also found that when the loop is free-running, the field amplitude is stable and no ponderomotive instabilities are present as long as the non-ideal effects are limited. When the loop is locked to an external phase and amplitude reference, ponderomotive instabilities can occur; however, the loop can be made stable by adjustment of the loop phase shift, and the stable range can be increased by using high amplitude andn be increased by using high amplitude and phase feedback gains. It is also found that under certain feedback conditions, the error on the particle energy gain can be made to vanish, although residual phase and amplitude errors are still present. A microprocessor-controlled feedback system based on this analysis is then described and results of experiments performed in conjunction with a 150 MHz lead (Pb) plated superconducting split-ring resonator are presented. The experiments show excellent agreement with the analysis
Energy Technology Data Exchange (ETDEWEB)
Munz, M., E-mail: martin.munz@npl.co.uk
2013-08-15
In this study, atomic force microscopy (AFM) has been employed to image a photopolymerized poly(ethylene glycol) diacrylate (PEG-DA) hydrogel. The same area was imaged both in amplitude modulation (AM) and in frequency modulation (FM) mode and the latter allowed for excellent resolution of the hydrogel microstructure. It shows globular domains with typical diameters in the range of ?10–100 nm. The hydrogel morphology has been analysed using grain size analysis as well as roughness analysis. Based on AFM topography images of hydrogel nano-domains, a set of roughness parameters has been identified which can be readily used as descriptors for spatial resolution. It includes the density of summits, S{sub ds}, the mean summit curvature, S{sub sc}, the surface area ratio, S{sub dr}, and the correlation length parameter, S{sub cl37}. The latter describes the length over which the autocorrelation function decays to 37% of its peak value. These parameters allow for better discrimination than the widely used root-mean-square (RMS) roughness, S{sub q}, and are available with common image processing software packages. Systematic variation of the virtual tilt angle has indicated that these parameters are robust to small variations in plane levelling. Such image processing is frequently needed to separate the inherent surface microstructure from the global topography related to sample tilt or surface waviness. Hydrogels are an important group of biomaterials as they find numerous applications in biomedical engineering, ranging from adhesives, to controlled release of water-soluble drugs, to encapsulation of cells, to tissue engineering. Optimisation of their interactions with bioentities, such as bacteria, cells or proteins, requires accurate surface characterisation.
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.
Giovagnetti, Vasco; Ware, Maxwell A; Ruban, Alexander V
2015-08-01
In their natural environment, plants are exposed to varying light conditions, which can lead to a build-up of excitation energy in photosystem (PS) II. Non-photochemical quenching (NPQ) is the primary defence mechanism employed to dissipate this excess energy. Recently, we developed a fluorescence-quenching analysis procedure that enables the protective effectiveness of NPQ in intact Arabidopsis leaves to be determined. However, pulse-amplitude modulation measurements do not currently allow distinguishing between PSII and PSI fluorescence levels. Failure to account for PSI contribution is suggested to lead to inaccurate measurements of NPQ and, particularly, maximum PSII yield (F v/F m). Recently, Pfündel et al. (Photosynth Res 114:189-206, 2013) proposed a method that takes into account PSI contribution in the measurements of F o fluorescence level. However, when PSI contribution was assumed to be constant throughout the induction of NPQ, we observed lower values of the measured minimum fluorescence level ([Formula: see text]) than those calculated according to the formula of Oxborough and Baker (Photosynth Res 54:135-142 1997) ([Formula: see text]), regardless of the light intensity. Therefore, in this work, we propose a refined model to correct for the presence of PSI fluorescence, which takes into account the previously observed NPQ in PSI. This method efficiently resolves the discrepancies between measured and calculated F o' produced by assuming a constant PSI fluorescence contribution, whilst allowing for the correction of the maximum PSII yield. PMID:25613087
Knapp, James E; Bonham, Michele A; Gibson, Quentin H; Nichols, Jeffry C; Royer, William E
2005-11-01
Residue F4 (Phe 97) undergoes the most dramatic ligand-linked transition in Scapharca dimeric hemoglobin, with its packing in the heme pocket in the unliganded (T) state suggested to be a primary determinant of its low affinity. Mutation of Phe 97 to Leu (previously reported), Val, and Tyr increases oxygen affinity from 8- to 100-fold over that of the wild type. The crystal structures of F97L and F97V show side chain packing in the heme pocket for both R and T state structures. In contrast, in the highest-affinity mutation, F97Y, the tyrosine side chain remains in the interface (high-affinity conformation) even in the unliganded state. Comparison of these mutations reveals a correlation between side chain packing in the heme pocket and oxygen affinity, indicating that greater mass in the heme pocket lowers oxygen affinity due to impaired movement of the heme iron into the heme plane. The results indicate that a key hydrogen bond, previously hypothesized to have a central role in regulation of oxygen affinity, plays at most only a small role in dictating ligand affinity. Equivalent mutations in sperm whale myoglobin alter ligand affinity by only 5-fold. The dramatically different responses to mutations at the F4 position result from subtle, but functionally critical, stereochemical differences. In myoglobin, an eclipsed orientation of the proximal His relative to the A and C pyrrole nitrogen atoms provides a significant barrier for high-affinity ligand binding. In contrast, the staggered orientation of the proximal histidine found in liganded HbI renders its ligand affinity much more susceptible to packing contacts between F4 and the heme group. These results highlight very different strategies used by cooperative hemoglobins in molluscs and mammals to control ligand affinity by modulation of the stereochemistry on the proximal side of the heme. PMID:16262242
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.
Bramucci, Anna R; Labeeuw, Leen; Mayers, Teaghan J; Saby, Julie A; Case, Rebecca J
2015-01-01
Conventional methods for experimental manipulation of microalgae have employed large volumes of culture (20 ml to 5 L), so that the culture can be subsampled throughout the experiment1-7. Subsampling of large volumes can be problematic for several reasons: 1) it causes variation in the total volume and the surface area:volume ratio of the culture during the experiment; 2) pseudo-replication (i.e., replicate samples from the same treatment flask8) is often employed rather than true replicates (i.e., sampling from replicate treatments); 3) the duration of the experiment is limited by the total volume; and 4) axenic cultures or the usual bacterial microbiota are difficult to maintain during long-term experiments as contamination commonly occurs during subsampling. The use of microtiter plates enables 1 ml culture volumes to be used for each replicate, with up to 48 separate treatments within a 12.65x8.5x2.2 cm plate, thereby decreasing the experimental volume and allowing for extensive replication without subsampling any treatment. Additionally, this technique can be modified to fit a variety of experimental formats including: bacterial-algal co-cultures, algal physiology tests, and toxin screening9-11. Individual wells with an alga, bacterium and/or co-cultures can be sampled for numerous laboratory procedures including, but not limited to: WATER-Pulse-Amplitude-Modulated (WATER-PAM) fluorometry, microscopy, bacterial colony forming unit (cfu) counts and flow cytometry. The combination of the microtiter plate format and WATER-PAM fluorometry allows for multiple rapid measurements of photochemical yield and other photochemical parameters with low variability between samples, high reproducibility and avoids the many pitfalls of subsampling a carboy or conical flask over the course of an experiment. PMID:25867634
Molokanova, E; Maddox, F; Luetje, C W; Kramer, R H
1999-06-15
Cyclic nucleotide-gated (CNG) channels are crucial for phototransduction in vertebrate rod photoreceptors. The cGMP sensitivity of these channels is modulated by diffusible intracellular messengers, including Ca2+/calmodulin, contributing to negative feedback during sensory adaptation. Membrane-associated protein tyrosine kinases and phosphatases also modulate rod CNG channels, but whether this results from direct changes in the phosphorylation state of the channel protein has been unclear. Here, we show that bovine rod CNG channel alpha-subunits (bRET) contain a tyrosine phosphorylation site crucial for modulation. bRET channels expressed in Xenopus oocytes exhibit modulation, whereas rat olfactory CNG channels (rOLF) do not. Chimeric channels reveal that differences in the C terminus, containing the cyclic nucleotide-binding domain, account for this difference. One specific tyrosine in bRET (Y498) appears to be crucial; replacement of this tyrosine in bRET curtails modulation, whereas installation into rOLF confers modulability. As the channel becomes dephosphorylated, there is an increase in the rate of spontaneous openings in the absence of ligand, indicating that changes in the phosphorylation state affect the allosteric gating equilibrium. Moreover, we find that dephosphorylation, which favors channel opening, requires open channels, whereas phosphorylation, which promotes channel closing, requires closed channels. Hence, modulation by changes in tyrosine phosphorylation is activity-dependent and may constitute a positive feedback mechanism, contrasting with negative feedback systems underlying adaptation. PMID:10366613
Residues in the 5th module of the low-density lipoprotein receptor that bind apoE and apoB-100
International Nuclear Information System (INIS)
Full text: The low-density lipoprotein receptor (LDLR) binds and removes cholesterol-rich lipoproteins from the circulation. Its ligand-binding (LB) domain consists of seven cysteine-rich LB modules that bind apoB-100 and apoE. These modules fold into well-defined structures with three disulfide bonds, in the presence of Ca2+. The 5th module (LB5) is unique in that it is required to bind both apoB-100 and apoE. The aim of the current study was to map residues in human LB5 that are required for ligand binding. This was done by alanine mutagenesis of a series of residues that are conserved in human, mouse, rat and rabbit LB5 (E9, S14, E16, H19, S21, K31, and K33), but not in the other six modules. E37 (R37 in the rabbit) was included, since it has been previously hypothesized to play a role in binding. The variant LB5 modules were first produced as recombinant peptides, and subjected to oxidative folding to determine whether the mutations interfered with Ca2+'-dependent folding. Only the S14A and E16A mutations interfered significantly with folding, suggesting that S14 and E16 are required for the structural framework of LB5 and that their substitution in the LDLR may interfere with its folding. The native LDLR and E9A, H19A, S21A, K31A, K33A and E37A LDLRs were expressed in LDLR negative IdlA-7 CHO cells. Labeling with 125I-lgG-C7 showed that all receptors were expressed on the cell surface. Binding of Dil-labeled LDL (Dil-LDL) and Dil-ding of Dil-labeled LDL (Dil-LDL) and Dil-labeled DMPC, complexed with the N-terminal receptor-binding domain of apoE3 (Dil-E3), at 4 deg C, was used to assess receptor binding. Binding of Dil-E3 (0.1 ?/ml) to the H19A, S21A, K31A, K33A and E37A LDLRs was 65-92% of binding to the native LDLR. In contrast, the E9A LDLR only bound 3% of that of the native LDLR. The binding of Dil-LDL (0.5 Ag/ml) to the E9A LDLR was 23% of that of the native LDLR, while binding to the remaining variant LDLRs ranged from 44-70% of what of the native LDLR. We conclude that (i) E9 of LB5 plays a key role in the binding of apoE and LDL, consistent with ionic interactions with basic residues on apoE and apoB-100. (ii) that H19, S21, K31, and K33 and E37 play a minor role in binding apoE, and (iii) that these residues play a small, but significant role in the binding of LDL
Price, Kerry L.; Lummis, Sarah C. R.
2014-01-01
GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using ...
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.
Wang, Xiao; Hao, Yan; Weinberg, Seth H; Smith, Gregory D
2015-06-01
Through theoretical analysis of the statistics of stochastic calcium (Ca(2+)) release (i.e., the amplitude, duration and inter-event interval of simulated Ca(2+) puffs and sparks), we show that a Langevin description of the collective gating of Ca(2+) channels may be a good approximation to the corresponding Markov chain model when the number of Ca(2+) channels per Ca(2+) release unit (CaRU) is in the physiological range. The Langevin description of stochastic Ca(2+) release facilitates our investigation of correlations between successive puff/spark amplitudes, durations and inter-spark intervals, and how such puff/spark statistics depend on the number of channels per release site and the kinetics of Ca(2+)-mediated inactivation of open channels. When Ca(2+) inactivation/de-inactivation rates are intermediate-i.e., the termination of Ca(2+) puff/sparks is caused by an increase in the number of inactivated channels-the correlation between successive puff/spark amplitudes is negative, while the correlations between puff/spark amplitudes and the duration of the preceding or subsequent inter-spark interval are positive. These correlations are significantly reduced or change signs when inactivation/de-inactivation rates are extreme (slow or fast) and puff/sparks terminate via stochastic attrition. PMID:25843352
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.
Pizzutti, Ionara R; Vreuls, René J J; de Kok, André; Roehrs, Rafael; Martel, Samile; Friggi, Caroline A; Zanella, Renato
2009-04-10
In this study, a new modulator that is simple, robust and presents low operation costs, was developed. This modulator uses compressed air to cool two small portions in the first centimeters of the second chromatographic column of a comprehensive multidimensional gas chromatography (GCxGC) system. The results show a variation in the peak area less than 3 and 5% to alkanes and pesticides, respectively. The standard deviations for the retention times in the first and second dimension are around 0.05 min and 0.05s for all the compounds. The system was optimized with n-alkanes. The GCxGC system proposed was applied in the determination of pyrethroid pesticides (bifenthrin, cypermethrin, deltamethrin, fenvalerate, esfenvalerate, cis- and trans-permethrin) in grape samples. Samples were extracted by the mini-Luke modified method and pesticides were quantified by comprehensive multidimensional gas chromatography with micro electron-capture detection (microECD). The values of method limit of quantification (LOQ) were 0.01-0.02 mg kg(-1) for all studied pyrethroid and the values of recovery were between 94.3 and 115.2%, with good precision (RSDair has the potential for application in the analysis of a wider range of pesticide residues in other commodities since it provides low values of LOQ with acceptable accuracy and precision. PMID:19233371
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.
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
Higher rank cylinder amplitude
International Nuclear Information System (INIS)
The dual topological unitarization is investigated for the case of any number of planar SU(N) singlet reggeons. In particular, the detailed structure of the cylinder amplitude is fully investigated. The planar bootstrap constraints are derived for the reggeon propagator and the triple reggeon vertex. The cylinder unitarization of planar poles is performed by means of the planar sewing method. The cylinder equation is described in terms of the factorizable kernel of finite rank. We are then led to the following typical properties of the cylinder. First, the cylinder partial wave amplitude is meromorphic in the J-plane. Secondly, extinction of the input SU(N) singlets is guaranteed. Thirdly, the cylinder residue is factorizable at all t. Fourthly, the cylindrical mixing is inevitable for the higher rank kernel. Moreover, the mixing phenomena are examined for the special case of the single daughter contribution. The repulsive [attractive] mixing pattern is expected to be observed between the even [odd] charge conjugation components of the cylindrically renormalized trajectories in the weak cylindrical mixing limit. (author)
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...
Goswami, Mithun; Madhu, P. K.
2008-06-01
Sensitivity enhancement of solid-state NMR spectrum of half-integer spin quadrupolar nuclei under both magic-angle spinning (MAS) and static cases has been demonstrated by transferring polarisation associated with satellite transitions to the central m = -1/2 ? 1/2 transition with suitably modulated radio-frequency pulse schemes. It has been shown that after the application of such enhancement schemes, there still remains polarisation in the satellite transitions that can be transferred to the central transition. This polarisation is available without having to wait for the spin system to return to thermal equilibrium. We demonstrate here the additional sensitivity enhancement obtained by making use of this remaining polarisation with fast amplitude-modulated (FAM) pulse schemes under both MAS and static conditions on a spin-3/2 and a spin-5/2 system. Considerable signal enhancement is obtained with the application of the multiple FAM sequence, denoted as m-FAM. We also report here some of the salient features of these multiple FAM sequences with respect to the nutation frequency of the pulses and the spinning frequency.
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...
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.
International Nuclear Information System (INIS)
The problem of the production of extended (?1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2–0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration (?100 ns), maintains the electron density at a level ne = (3–5) × 1014 cm—3 by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy (?0.5 eV) and a long lifetime (?1 ms), which are produced upon cessation of the laser pulse. (extreme light fields and their appllight fields and their applications)
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?.
Directory of Open Access Journals (Sweden)
O. Uchino
2013-02-01
Full Text Available Simultaneous measurements of the partial column-averaged dry air mixing ratio of CO2 (XCO2 and target range were demonstrated using airborne amplitude-modulated 1.57 ?m differential laser absorption spectrometer (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 atmospheric CO2 measurements. A high correlation coefficient (R of 0.987 between XCO2 observed by LAS and XCO2 calculated from in situ measurements was obtained. The averaged difference in XCO2 obtained from LAS and validation data was within 1.5 ppm for all spiral measurements. An interesting vertical profile was observed for both XCO2LAS and XCO2val, 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 there are boundary-layer enhanced CO2 and aerosol in the winter, the difference of XCO2LAS to XCO2val is a negative bias of 1.5 ppm, and XCO2LAS is in agreement with XCO2val within the measurement precision of 2.4 ppm (1 SD.
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)
Apostol, Marcin I.; Sawaya, Michael R.; Cascio, Duilio; Eisenberg, David (UCLA)
2010-09-23
A single nucleotide polymorphism (SNP) in codon 129 of the human prion gene, leading to a change from methionine to valine at residue 129 of prion protein (PrP), has been shown to be a determinant in the susceptibility to prion disease. However, the molecular basis of this effect remains unexplained. In the current study, we determined crystal structures of prion segments having either Met or Val at residue 129. These 6-residue segments of PrP centered on residue 129 are 'steric zippers,' pairs of interacting {beta}-sheets. Both structures of these 'homozygous steric zippers' reveal direct intermolecular interactions between Met or Val in one sheet and the identical residue in the mating sheet. These two structures, plus a structure-based model of the heterozygous Met-Val steric zipper, suggest an explanation for the previously observed effects of this locus on prion disease susceptibility and progression.
Superlinear Amplitude Amplification
Grover, Lov K.
2008-01-01
Quantum search/amplitude amplification algorithms are designed to be able to amplify the amplitude in the target state linearly with the number of operations. Since the probability is the square of the amplitude, this results in the success probability rising quadratically with the number of operations. This paper presents a new kind of quantum search algorithm in which the amplitude of the target state, itself increases quadratically with the number of operations. However, ...
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.)
Diphoton Generalized Distribution Amplitudes
Beiyad, M. El; Pire, B.; Szymanowski, L.; Wallon, S.
2008-01-01
We calculate the leading order diphoton generalized distribution amplitude by calculating the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region at the Born order and in the leading logarithmic approximation. As in the case of the anomalous photon structure functions, the gamma gamma generalized distribution amplitude exhibits a characteristic \\ln Q^2 behaviour and obeys inhomogeneous evolution equations.
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.
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
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 method is illustrated for two-amplitude loads by means of experimental results obtained by testing specimens of a structural steel and is shown to be more accurate than the Palmgren-Miner cumulative damage method.
Two Photon Distribution Amplitudes
Beiyad, M. El; Pire, B.; Szymanowski, L.; Wallon, S.
2008-01-01
The factorization of the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region is demonstrated at the Born order and in the leading logarithmic approximation. The leading order two photon (generalized) distribution amplitudes exhibit a characteristic ln Q2 behaviour and obey new inhomogeneous evolution equations.
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.
Amplitude dependent damping in single crystalline high purity molybdenum
International Nuclear Information System (INIS)
Amplitude dependent damping measurements were performed on high purity single crystalline molybdenum at several different constant temperatures between room temperature and 1273K. The employed samples were single crystals with the orientation, having a residual resistivity ratio of about 8000. Previously to the amplitude dependent damping tests, the samples were subjected to different thermomechanical histories. Amplitude dependent damping effects appear only during the first heating run in temperature where the samples have the thermomechanical state of the deformation process at room temperature. In the subsequent run-ups in temperature, i.e, after subsequent annealings, amplitude dependent damping effects were not detected (au)
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.)
Modified ? ? amplitude with ? pole
Bydžovský, P.; Kami?ski, R.; Nazari, V.
2014-12-01
A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (? ? , K K ¯, and ? ? ) and P (? ? , ? 2 ? , and ? ? ) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the ? ? threshold region. Moreover, the pole of the S wave amplitude related with the f0(500 ) meson (former f0(600 ) or ? ) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the ? pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, ? ? amplitudes with a heavy and broad ? meson without changing of their original mathematical structure.
Improved cardiac phase/amplitude functional imaging
International Nuclear Information System (INIS)
In multiple gated cardiac bloodpool studies using sup(99m)Tc, the motility of the ventricles may be assessed by functional imaging by temporal Fourier analysis. In the present study some theoretical and practical objections to this computation and presentation scheme are overcome. The method provides by a more realistic model, requires only a black and white display (video or plotter) and produces amplitude modulation of the phase image, thus combining the two images into one. Amplitude modulated phase maps allow presentation of information that is essentially dynamic of nature in a hard-copy black and white format. These maps serve as patient documentation which is more easily accessible than digital storage media or videotapes. (UK)
Nonlocal Modulation of Entangled Photons
Harris, S. E.
2008-01-01
We consider ramifications of the use of high speed light modulators to questions of correlation and measurement of time-energy entangled photons. Using phase modulators, we find that temporal modulation of one photon of an entangled pair, as measured by correlation in the frequency domain, may be negated or enhanced by modulation of the second photon. Using amplitude modulators we describe a Fourier technique for measurement of biphoton wave functions with slow detectors.
High amplitude propagated contractions.
Bharucha, A E
2012-11-01
While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. High amplitude propagated contractions occur spontaneously, in response to pharmacological agents or colonic distention. A subset of patients with slow transit constipation have fewer HAPC. In this issue of Neurogastroenterology and Motility, Rodriguez et al. report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in constipated children undergoing colonic manometry. Moreover, and consistent with a neural mechanism, anal relaxation often precedes arrival of HAPC in the left colon. High amplitude propagated contractions are also used to evaluate the motor response to a meal and pharmacological stimuli (e.g., bisacodyl, neostigmine) and to identify colonic inertia during colonic motility testing in chronic constipation. This editorial comprehensively reviews the characteristics, physiology and pharmacology of HAPC, their assessment by manometry, and relevance to constipation and diarrhea. PMID:23057554
International Nuclear Information System (INIS)
A summary is presented of the many investigations that have been done on solid residues of atmospheric fluid bed combustion (AFBC). These residues are bed ash, cyclone ash and bag filter ash. Physical and chemical properties are discussed and then the various uses of residues (in fillers, bricks, gravel, and for recovery of aluminium) are summarised. Toxicological properties of fly ash and stack ash are discussed as are risks of pneumoconiosis for workers handling fly ash, and contamination of water by ashes. On the basis of present information it is concluded that risks to public health from exposure to emissions of coal fly ash from AFBC appear small or negligible as are health risk to workers in the coal fly ash processing industry. 35 refs., 5 figs., 12 tabs
International Nuclear Information System (INIS)
This article discusses the partial wave analysis of two, three and four meson systems. The difference between the two approaches, referred to as amplitude and Ascoli analysis is discussed. Some of the results obtained with these methods are shown. (B.R.H.)
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
Reinforcing Saccadic Amplitude Variability
Paeye, Celine; Madelain, Laurent
2011-01-01
Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…
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)
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...
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.
Dual Amplitude-Width PPM for Free Space Optical Systems
Directory of Open Access Journals (Sweden)
Mehdi Rouissat
2012-04-01
Full Text Available The PPM (Pulse Position Modulation is commonly used in Free Space Optic (FSO systems owing to its power efficiency, but it shows a rapid decline in spectral efficiency with increase in the power efficiency and moderate data rate. In order to improve these two parameters, we present a modified modulation scheme of the existing PPM, on the basis of PPM, PAM (Pulse Amplitude Modulation and PWM (Pulse Width Modulation. This modified version called DAWPPM (Dual Amplitude-Width PPM.The average power requirements, bandwidth efficiency and normalized data rate are studied after introducing symbol structure. The proposed scheme shows an improvement in terms of data rate and bandwidth efficiency, and when in come to power efficiency it shows lower efficiency compared to PPM. We present theoretical expressions of data rate, spectral efficiency, and normalized power requirements, and we present comparison results to PPM modulation scheme.
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.
Connection between the period and the amplitude of the Blazhko effect
Benk?, J M
2014-01-01
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)
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)
HIGH AMPLITUDE PROPAGATED CONTRACTIONS
Adil E. Bharucha
2012-01-01
While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. HAPC occur spontaneously, in response to pharmacological agents or colonic distention. In this issue of Neurogastroenterology and Motility, Rodriguez and colleagues report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in const...
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...
Renormalization of massless Feynman amplitudes in configuration space
Nikolov, Nikolay M.; Stora, Raymond; Todorov, Ivan
2014-05-01
A systematic study of recursive renormalization of Feynman amplitudes is carried out both in Euclidean and in Minkowski configuration spaces. For a massless quantum field theory (QFT), we use the technique of extending associate homogeneous distributions to complete the renormalization recursion. A homogeneous (Poincaré covariant) amplitude is said to be convergent if it admits a (unique covariant) extension as a homogeneous distribution. For any amplitude without subdivergences — i.e. for a Feynman distribution that is homogeneous off the full (small) diagonal — we define a renormalization invariant residue. Its vanishing is a necessary and sufficient condition for the convergence of such an amplitude. It extends to arbitrary — not necessarily primitively divergent — Feynman amplitudes. This notion of convergence is finer than the usual power counting criterion and includes cancellation of divergences.
Renormalization of Massless Feynman Amplitudes in Configuration Space
Nikolov, Nikolay M; Todorov, Ivan
2013-01-01
A systematic study of recursive renormalization of Feynman amplitudes is carried out both in Euclidean and in Minkowski configuration space. For a massless quantum field theory (QFT) we use the technique of extending associate homogeneous distributions to complete the renormalization recursion. A homogeneous (Poincare covariant) amplitude is said to be convergent if it admits a (unique covariant) extension as a homogeneous distribution. For any amplitude without subdivergences - i.e. for a Feynman distribution that is homogeneous off the full (small) diagonal - we define a renormalization invariant residue. Its vanishing is a necessary and sufficient condition for the convergence of such an amplitude. It extends to arbitrary - not necessarily primitively divergent - Feynman amplitudes. This notion of convergence is finer than the usual power counting criterion and includes cancellation of divergences.
Effect of Modulation Error on All Optical Fiber Current Transformers
Zhengping Wang; Yuekun Wang; Shuai Sun
2012-01-01
For actively modulated In-line Sagnac interferential all optic fiber current transformers (AOFCTs), the accuracies are directly affected by the amplitude of the modulation signal. In order to deeply undertand the function of the modulator, a theoretical model of modulation effect to AOFCTs is built up in this paper. The effect of the amplitude of the modulation signal to the output intensity of AOFCTs is theoretically formulated and numerical calculated. The results show that the modulation v...
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.
Cross-phase modulation imaging
Samineni, Prathyush; Li, Baolei; Wilson, Jesse W.; WARREN, WARREN S.; Fischer, Martin C.
2012-01-01
We demonstrate a cross-phase modulation measurement technique based on the sensitive detection of modulation transfer in a pump-probe setup. By modulating the amplitude of the pump beam and spectrally analyzing the probe beam, we achieve a rapid, background-free measurement of nonlinear phase modulation using power levels acceptable in biological imaging. This measurement technique would allow the extension of widely employed phase microscopy methods to the nonlinear regime, providing intrins...
Glauber amplitude calculation method
International Nuclear Information System (INIS)
In the framework of eikonal approach the problem of calculating cross section of the composed system quasielastic scattering is considered. The one-particle densities of the system as well as the constituent elastic scattering amplitude are given by Gaussian functions. The calculation algorithm of these cross sections based on using diagram, representation of Glauber expansion terms is proposed. By this algorithm after having integrated the multidimensional Gaussian functions by any coordinate of constituent system a concept of a scattering diagram was used. It enables one to execute reducing of similar members of Glauber series
Amplitude equations for stochastic partial differential equations
Blömker, Dirk
2007-01-01
Rigorous error estimates for amplitude equations are well known for deterministic PDEs, and there is a large body of literature over the past two decades. However, there seems to be a lack of literature for stochastic equations, although the theory is being successfully used in the applied community, such as for convective instabilities, without reliable error estimates at hand. This book is the first step in closing this gap. The author provides details about the reduction of dynamics to more simpler equations via amplitude or modulation equations, which relies on the natural separation of time-scales present near a change of stability. For students, the book provides a lucid introduction to the subject highlighting the new tools necessary for stochastic equations, while serving as an excellent guide to recent research.
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.
Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul
2014-01-01
A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003
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.
B-meson distribution amplitudes
Grozin, A. G.
2005-01-01
B-meson light-cone distribution amplitudes are discussed in these lectures in the framework of HQET. The evolution equation for the leading-twist distribution amplitude is derived in one-loop approximation. QCD sum rules for distribution amplitudes are discussed.
Closed string amplitudes as single-valued open string amplitudes
International Nuclear Information System (INIS)
We show that the single trace heterotic N-point tree-level gauge amplitude ANHET can be obtained from the corresponding type I amplitude ANI by the single-valued (sv) projection: ANHET=sv(ANI). This projection maps multiple zeta values to single-valued multiple zeta values. The latter represent a subclass of multiple zeta values originating from single-valued multiple polylogarithms at unity. Similar relations between open and closed string amplitudes or amplitudes of different string vacua can be established. As a consequence the ??-expansion of a closed string amplitude is dictated by that of the corresponding open string amplitude. The combination of single-valued projections, Kawai–Lewellen–Tye relations and Mellin correspondence reveal a unity of all tree-level open and closed superstring amplitudes together with the maximally supersymmetric Yang–Mills and supergravity theories
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
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 air.
International Nuclear Information System (INIS)
Purpose: To report early clinical outcomes of helical tomotherapy (HT)-based image-guided intensity-modulated radiation therapy (IMRT) in brain tumors of varying shape, size, and location. Materials and Methods: Patients with residual, recurrent, and/or progressive low-grade intracranial and skull-base tumors were treated on a prospective protocol of HT-based IMRT and followed clinicoradiologically. Standardized metrics were used for plan evaluation and outcome analysis. Results: Twenty-seven patients with 30 lesions were treated to a median radiotherapy dose of 54 Gy in 30 fractions. All HT plans resulted in excellent target volume coverage with steep dose-gradients. The mean (standard deviation) dose homogeneity index and conformity index was 0.07 (0.05) and 0.71 (0.08) respectively. At first response assessment, 20 of 30 lesions were stable, whereas 9 showed partial regression. One patient with a recurrent clival chordoma though neurologically stable showed imaging-defined progression, whereas another patient with stable disease on serial imaging had sustained neurologic worsening. With a median follow-up of 19 months (interquartile range, 11–26 months), the 2-year clinicoradiological progression-free survival and overall survival was 93.3% and 100% respectively. Conclusions: Careful selection of radiotherapy technique is warranted for benign/low-grade brain tumors to achieve durable local control with minimum long-term morbidity. Large or complex-shaped tumors bbidity. Large or complex-shaped tumors benefit most from IMRT. Our early clinical experience of HT-based IMRT for brain tumors has been encouraging.
Cross-Modulation Interference with Lateralization of Mixed-Modulated Waveforms
Hsieh, I-Hui; Petrosyan, Agavni; Goncalves, Oscar F.; Hickok, Gregory; Saberi, Kourosh
2010-01-01
Purpose: This study investigated the ability to use spatial information in mixed-modulated (MM) sounds containing concurrent frequency-modulated (FM) and amplitude-modulated (AM) sounds by exploring patterns of interference when different modulation types originated from different loci as may occur in a multisource acoustic field. Method:…
International Nuclear Information System (INIS)
Analysis of the registered energy amplitudes measured with silicon radiation detector with the significant pulse height defect (PHD), namely for the evaporation residues (EVR) and fission fragments (FF), has been performed for rare events obtained in the heavy ion induced nuclear reactions. It is shown that in some cases those measured amplitudes are quite anomalous
Large Amplitude Oscillations in Prominences
Tripathi, D; Jain, R
2009-01-01
Since the first reports of oscillations in prominences in 1930s there have been major theoretical and observational advances to understand the nature of these oscillatory phenomena leading to a whole new field of so called "prominence seismology". There are two types of oscillatory phenomena observed in prominences; "small amplitude oscillations" (~2-3 km s$^{-1}$) which are quite common and "large amplitude oscillations" ($>$20 km s$^{-1}$) for which observations are scarce. Large amplitude oscillations have been found as "winking filament" in H$\\alpha$ as well as motion in the sky plane in H$\\alpha$, EUV, micro-wave and He 10830 observations. Historically, it was suggested that the large amplitude oscillations in prominences were triggered by disturbances such as fast-mode MHD waves (Moreton wave) produced by remote flares. Recent observations show, in addition, that near-by flares or jets can also create such large amplitude oscillations in prominences. Large amplitude oscillations, which are observed both...
Lonngren, Karl E.
1987-07-01
Velocity modulation of an electron beam, which is the underlying physical phenomena for various microwave tubes such as klystrons and magnetrons, is interpreted in terms of a water bag model which has its origin in plasma physics. Using this technique, it is possible to estimate the expected amplitude for a velocity-modulated electron beam.
Motivic amplitudes and cluster coordinates
Golden, J. Department Of Physics; Goncharov, A.; Spradlin, M.; Vergu, C.; Volovich, A.
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...
Rodrigues Ferreira, Elizabete; Boulanger, Philippe; Destrade, Michel
2008-01-01
In the context of the finite elasticity theory, we consider a model for compressible solids called 'compressible neo-Hookean material'. We show how finite-amplitude inhomogeneous plane wave solutions and finite-amplitude unattenuated solutions can combine to form a finite-amplitude Love wave. We take a layer of finite thickness overlying a solid half-space, both made of different prestressed compressible neo-Hookean materials. We derive an exact solution of the equations of ...
Graviton amplitudes from collinear limits of gauge amplitudes
Directory of Open Access Journals (Sweden)
Stephan Stieberger
2015-05-01
Full Text Available We express all tree-level graviton amplitudes in Einstein's gravity as the collinear limits of a linear combination of pure Yang–Mills amplitudes in which each graviton is represented by two gauge bosons, each of them carrying exactly one half of graviton's momentum and helicity.
On the Period-Amplitude and Amplitude-Period Relationships
Wilson, Robert M.; Hathaway, David H.
2008-01-01
Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.
International Nuclear Information System (INIS)
It is proposed to use a dynatron effect to modulate the voltage across the vacuum inverted coaxial diode with magnetic insulation supplied by an external pulsed high-voltage source connected to the modulator via the RL-circuit. Oscillations of the voltage due to oscillating regime of diode charging and/or azimuthal instability of a rotating electron flow simulates back-bombardment electron flow to the cathode and leads to power spikes of secondary emission current exceeding the primary one. As a result,the amplitude of oscillations grows and the system can turn the modulator and its possible applications
Agafonov, A V
2001-01-01
It is proposed to use a dynatron effect to modulate the voltage across the vacuum inverted coaxial diode with magnetic insulation supplied by an external pulsed high-voltage source connected to the modulator via the RL-circuit. Oscillations of the voltage due to oscillating regime of diode charging and/or azimuthal instability of a rotating electron flow simulates back-bombardment electron flow to the cathode and leads to power spikes of secondary emission current exceeding the primary one. As a result,the amplitude of oscillations grows and the system can turn the modulator and its possible applications.
Double-cut of scattering amplitudes and Stokes' Theorem
International Nuclear Information System (INIS)
We show how Stokes' Theorem, in the fashion of the Generalised Cauchy Formula, can be applied for computing double-cut integrals of one-loop amplitudes analytically. It implies the evaluation of phase-space integrals of rational functions in two complex-conjugated variables, which are simply computed by an indefinite integration in a single variable, followed by Cauchy's Residue integration in the conjugated one. The method is suitable for the cut-construction of the coefficients of 2-point functions entering the decomposition of one-loop amplitudes in terms of scalar master integrals.
Recognition of OFDM Modulation Method
Directory of Open Access Journals (Sweden)
K. Ulovec
2008-04-01
Full Text Available This contribution deals with asynchronous noncoherent recognition of modulation types. The main aim is to recognize OFDM modulation method from some other single-carrier analog and digital modulation types in the presence of AWGN noise. The described solution of recognizer uses key features of the received signal. The signal amplitude is observed at the output of the quadrature intermediate-frequency stage. The properties of the recognizer are verified by simulations using Matlab.
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.
Directory of Open Access Journals (Sweden)
Gang Fang
2009-06-01
Full Text Available 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
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
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...
Approximating chiral SU(3) amplitudes
International Nuclear Information System (INIS)
We construct large-Nc motivated approximate chiral SU(3) amplitudes of next-to-next-to-leading order. The amplitudes are independent of the renormalisation scale. Fitting lattice data with those amplitudes allows for the extraction of chiral coupling constants with the correct scale dependence. The differences between approximate and full amplitudes are required to be at most of the order of N3LO contributions numerically. Applying the approximate expressions to recent lattice data for meson decay constants, we determine several chiral couplings with good precision. In particular, we obtain a value for F0, the meson decay constant in the chiral SU(3) limit, that is more precise than all presently available determinations. (orig.)
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 Lifshitz spacetime
International Nuclear Information System (INIS)
We consider the calculation of scattering amplitudes in field theories dual to Lifshitz spacetimes. These amplitudes provide an interesting probe of the IR structure of the field theory; our aim is to use them to explore the observable consequences of the singularity in the spacetime. We assume the amplitudes can be related by T-duality to a Wilson loop, as in the AdS case, and determine the bulk minimal surfaces for the simplest cusp Wilson loop. We use this to determine the leading IR singularity in the amplitude. We find there is a stronger IR singularity for z>1 than for z = 1, with a coefficient that vanishes as z?1. (paper)
Amplitude death state for hearing
Ahn, Kang-Hun
2012-01-01
We propose amplitude death phenomenon as an underlying mechanism of auditory transduction. When non-identical auditory hair bundles are elastically coupled, their spontaneous oscillations can be quenched to form an amplitude death state. We show, in this state, the hair cells are quiet and ready to detect oscillatory stimulus with coupling-strength dependent amplification. Numerical demonstration of the mechanism suggests that the non-uniformity of coupled hair cells can contribute to noise-robust auditory transduction.
Motivic amplitudes and cluster coordinates
Golden, J. K.; Goncharov, A. B.; Spradlin, M.; Vergu, C.; Volovich, A.
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 (?3) underlies the structure of motivic amplitudes. Specifically, we compute explicitly the coproduct of the two-loop seven-particle MHV motivic amplitude and find that like the previously known six-particle amplitude, it depends only on certain preferred coordinates known in the mathematics literature as cluster - coordinates on Conf n (?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 being expressible in terms of classical polylogarithms is most naturally represented by certain quadrilateral faces of the appropriate associahedron. We also find and prove the first known functional equation for the trilogarithm in which all 40 arguments are cluster -coordinates of a single algebra. In this respect it is similar to Abel's 5-term dilogarithm identity.
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
Linearized Bragg grating assisted electro-optic modulator.
Khurgin, Jacob B; Morton, Paul A
2014-12-15
We propose a new linearized electro-optic modulator in which linearization is achieved by modulating the index of a Bragg grating reflector placed in the arm(s) of a Michelson Interferometer. This grating-assisted Michelson (GAMI) modulator can operate as either an intensity or amplitude modulator, and is shown to significantly improve the linearity of microwave photonics links. PMID:25503037
Modulation and detection of optical signals
Goodwin, F. E.
1972-01-01
A summary of information is presented which is related to the modulation and detection of information on optical carriers. It emphasizes the treatment of information transfer through an entire system. The most common configurations are considered: intensity modulation, amplitude modulation, frequency or phase modulation, and both direct and coherent detection. In assessing these configurations information capacity and message signal-to-noise ratio are used as a basis of comparison. The physical and geometric treatment of optical heterodyne (or coherent) detection is given.
Generator coordinate amplitude for scattering
International Nuclear Information System (INIS)
In the generator coordinate method for scattering the proper boundary conditions is accomplished by requiring the GC amplitude to satisfy an integral equation of the first kind. Attempts to solve this problem are first reviewed and then an improved approximation is proposed which is applicable to a wider class of scattering problems in addition to the Coulomb scattering. A better approximation is obtained in the asymptotic region, where the generator coordinate, i.e., the distance between two shell-model wells of the fragments, is larger than the touching distance of the colliding nuclei, by deriving partial differential equations of first order for the terms of an asymptotic series in 1/E, where E is the scattering energy. Extracting the information on the GC amplitude for small values of the generator parameter from the integral equation of the first kind is an ill-posed problem. It is shown that the method of statistical regularization offers a powerful and controllable procedure to uncover the GC amplitude. The unknown GC amplitude is treated as a random function with an a priori distribution of probability which is based on the assumption that the amplitude is bounded and that the errors in the input are random with zero expectation value. A useful procedure is found for fixing parameters of the a priori distribution. The solution for small values of the GC parameter is expressed in the form of a Dini series. The method is applied to the calculation of the GC amps applied to the calculation of the GC amplitude for scattering of two ?-particles at 15 MeV c.m. energy. The measure of the accuracy is the difference between the input wave function of relative motion and the result of folding of the GC amplitude with the kernel of the integral equation. The prescribed accuracy is reached with this method on a much larger interval than with any previously proposed method. (orig.)
Generator coordinate amplitude for scattering
Energy Technology Data Exchange (ETDEWEB)
Mihailovic, M.V.; Poljsak, M. (Institut Jozef Stefan, Ljubljana (Yugoslavia))
1982-10-25
In the generator coordinate method for scattering the proper boundary conditions is accomplished by requiring the GC amplitude to satisfy an integral equation of the first kind. Attempts to solve this problem are first reviewed and then an improved approximation is proposed which is applicable to a wider class of scattering problems in addition to the Coulomb scattering. A better approximation is obtained in the asymptotic region, where the generator coordinate, i.e., the distance between two shell-model wells of the fragments, is larger than the touching distance of the colliding nuclei, by deriving partial differential equations of first order for the terms of an asymptotic series in 1/E, where E is the scattering energy. Extracting the information on the GC amplitude for small values of the generator parameter from the integral equation of the first kind is an ill-posed problem. It is shown that the method of statistical regularization offers a powerful and controllable procedure to uncover the GC amplitude. The unknown GC amplitude is treated as a random function with an a priori distribution of probability which is based on the assumption that the amplitude is bounded and that the errors in the input are random with zero expectation value. A useful procedure is found for fixing parameters of the a priori distribution. The solution for small values of the GC parameter is expressed in the form of a Dini series. The method is applied to the calculation of the GC amplitude for scattering of two ..cap alpha..-particles at 15 MeV c.m. energy. The measure of the accuracy is the difference between the input wave function of relative motion and the result of folding of the GC amplitude with the kernel of the integral equation. The prescribed accuracy is reached with this method on a much larger interval than with any previously proposed method.
AMPLITUDE AND PHASE MODULATION FOR ULTRASONIC WIRELESS COMMUNICATION
Nan Gao; Shigeru Shimamoto
2014-01-01
Short range wireless communications have been used more and more frequently in our life. But the electromagnetic fields waves also have some disadvantages. One of these disadvantages is health problems. Many studies shows the electromagnetic field waves using for communication may damage our health. And in most hospitals, they also have bans on the use of mobile phones and wide area networks because of Electromagnetic Interference. So this paper studied the use of ultrasound f...
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
Finite Amplitude Electron Plasma Waves in a Cylindrical Waveguide
DEFF Research Database (Denmark)
Juul Rasmussen, Jens
1978-01-01
The nonlinear behaviour of the electron plasma wave propagating in a cylindrical plasma waveguide immersed in an infinite axial magnetic field is investigated using the Krylov-Bogoliubov-Mitropolsky perturbation method, by means of which is deduced the nonlinear Schrodinger equation governing the long-time slow modulation of the wave amplitude. From this equation the amplitude-dependent frequency and wavenumber shifts are calculated, and it is found that the electron waves with short wavelengths are modulationally unstable with respect to long-wavelength, low-frequency perturbations. It is further shown that an oscillatory solution of the Korteweg-de Vries equation, which is derived in the small wavenumber region, satisfies the small wavenumber limit of the nonlinear Schrodinger equation
Fringe-free holographic measurements of large-amplitude vibrations.
Joud, F; Verpillat, F; Laloë, F; Atlan, M; Hare, J; Gross, M
2009-12-01
In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; because of the limited resolution of the 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 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 rad have been measured. PMID:19953166
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 NHMV amplitudes
Belitsky, A V
2014-01-01
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 respected to the R-symmetry group and provide solutions to them to all orders in 't Hooft coupling. These are then successfully confronted against available low-loop perturbative calculations for NMHV amplitudes.
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.
Ferreira, Elizabete Rodrigues; Destrade, Michel; 10.1093/qjmam/hbn013
2008-01-01
In the context of the finite elasticity theory, we consider a model for compressible solids called 'compressible neo-Hookean material'. We show how finite-amplitude inhomogeneous plane wave solutions and finite-amplitude unattenuated solutions can combine to form a finite-amplitude Love wave. We take a layer of finite thickness overlying a solid half-space, both made of different prestressed compressible neo-Hookean materials. We derive an exact solution of the equations of motion and boundary conditions and also obtain results for the energy density and the energy flux of the waves. Finally, we investigate the special case when the interface between the layer and the substrate is in a principal plane of the prestrain. A numerical example is given.
OPE for all Helicity Amplitudes
Basso, Benjamin; Cordova, Lucia; Sever, Amit; Vieira, Pedro
2014-01-01
We extend the Operator Product Expansion (OPE) for scattering amplitudes in planar N=4 SYM to account for all possible helicities of the external states. This is done by constructing a simple map between helicity configurations and so-called charged pentagon transitions. These OPE building blocks are generalizations of the bosonic pentagons entering MHV amplitudes and they can be bootstrapped at finite coupling from the integrable dynamics of the color flux tube. A byproduct of our map is a simple realization of parity in the super Wilson loop picture.
Toward Complete Pion Nucleon Amplitudes
Mathieu, V; Fernández-Ramírez, C; Pennington, M R; Schott, D; Szczepaniak, A P; Fox, G
2015-01-01
We compare the low-energy partial wave analyses $\\pi N$ 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.
Scattering amplitudes in gauge theories
Energy Technology Data Exchange (ETDEWEB)
Henn, Johannes M. [Institute for Advanced Study, Princeton, NJ (United States). School of Natural Sciences; Plefka, Jan C. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik
2014-03-01
First monographical text on this fundamental topic. Course-tested, pedagogical and self-contained exposition. Includes exercises and solutions. At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge. These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum field theory. Bridging the gap between introductory courses on quantum field theory and state-of-the-art research, these concise yet self-contained and course-tested lecture notes are well-suited for a one-semester graduate level course or as a self-study guide for anyone interested in fundamental aspects of quantum field theory and its applications. The numerous exercises and solutions included will help readers to embrace and apply the material presented in the main text.
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)
Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly
Nikolov, Nikolay M; Todorov, Ivan
2013-01-01
Configuration (x-)space renormalization of Euclidean Feynman amplitudes in a massless quantum field theory is reduced to the study of local extensions of associate homogeneous distributions. Primitively divergent graphs are renormalized, in particular, by subtracting the residue of an analytically regularized expression. Examples are given of computing residues that involve zeta values. The renormalized Green functions are again associate homogeneous distributions of the same degree that transform under indecomposable representations of the dilation group.
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.
Periodic instantons and scattering amplitudes
International Nuclear Information System (INIS)
We discuss the role of periodic euclidean solutions with two turning points and zero winding number (periodic instantons) in instanton induced processes below the sphaleron energy Esph. We find that the periodic instantons describe certain multiparticle scattering events leading to the transitions between topologically distinct vacua. Both the semiclassical amplitudes and inital and final states of these transitions are determined by the periodic instantons. Furthermore, the corresponding probabilities are maximal among all states of given energy. We show that at E ? Esph, the periodic instantons can be approximated by infinite chains of ordinary instantons and anti-instantons, and they naturally emerge as deformations of the zero energy instanton. In the framework of 2d abelian Higgs model and 4d electroweak theory we show, however, that there is not obvious relation between periodic instantons and two-particle scattering amplitudes. (orig.)
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.
Genus dependence of superstring amplitudes
International Nuclear Information System (INIS)
The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |Kn|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived
Constraints on string resonance amplitudes
Cheung, Kingman; 10.1103/PhysRevD.72.015010
2005-01-01
We perform a global analysis of the tree-level open-string amplitudes in the limit sor=0.69-1.96 TeV at 95% confidence level for the Chan-Paton factors ¿T¿=0-4. We also estimate the expected sensitivities at the CERN LHC, which can be as high as 19 TeV for ¿T¿=4. (28 refs).
Transition Distribution Amplitudes for ??? collisions
Lansberg, J. P.; Pire, B.; Szymanowski, L.
2008-11-01
We study the exclusive production of ?? and ?? in hard ??? scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of Transition Distribution Amplitudes (TDA) is used to perform a QCD calculation of these reactions thanks to two simple models for TDAs. The sizable cross sections for ?? and ?? production may be tested at intense electron-positron colliders such as CLEO and B factories (Belle and BABAR).
International Nuclear Information System (INIS)
A Waveform Sampler Module (WSM) for the measurement of signal shapes coming from the multi-hit drift chambers of the SLAC SLC detector is described. The module uses a high speed, high resolution analog storage device (AMU) developed in collaboration between SLAC and Stanford University. The AMU devices together with high speed TTL clocking circuitry are packaged in a hybrid which is also suitable for mounting on the detector. The module is in CAMAC format and provides eight signal channels, each recording signal amplitude versus time in 512 cells at a sampling rate of up to 360 MHz. Data are digitized by a 12-bit ADC with a 1 ?s conversion time and stored in an on-board memory accessible through CAMAC
Time-frequency-modulation representation of stochastic signals
Jackson, Pjb
2007-01-01
When a noise process is modulated by a deterministic signal, it is often useful to determine the signal's parameters. A method of estimating the modulation index m is presented for noise whose amplitude is modulated by a periodic signal, using the magnitude modulation spectrum (MMS). The method is developed for application to real discrete signals with time- varying parameters, and extended to a 3D time-frequency- modulation representation. In contrast to squared-signal approaches, MMS behave...
Leading Singularities of the Two-Loop Six-Particle MHV Amplitude
Cachazo, Freddy; Volovich, Anastasia
2008-01-01
We use the leading singularity technique to determine the planar six-particle two-loop MHV amplitude in N=4 super Yang-Mills in terms of a simple basis of integrals. Our result for the parity even part of the amplitude agrees with the one recently presented in arXiv:0803.1465. The parity-odd part of the amplitude is a new result. The leading singularity technique reduces the determination of the amplitude to finding the solution to a system of linear equations. The system of equations is easily found by computing residues. We present the complete system of equations which determines the whole amplitude, and solve the two-by-two blocks analytically. Larger blocks are solved numerically in order to test the ABDK/BDS iterative structure.
Modulation ENDOR in monocrystals
International Nuclear Information System (INIS)
The results of the detail experimental and theoretical studies of the effect of HF modulation H0 on the properties of the electron nuclear double resonance (ENDOR) signal are presented. This signal was registered at the modulation frequency by the method of synchronous rectification. A new ENDOR mechanism is found out. This mechanism is connected with resonance amplification of modulation absorption of the paramagnetic centre (PC) system on switching the radio frequency (RF) field but not with the resonance change of relaxation electron spin characteristics. The sign of the effect depends on the values of the modulation amplitude and frequency. The modulation ENDOR is free from limitations of the relaxation ENDOR and may exceed the latter by the magnitude of the effect. The necessary condition of its existence is the difference of longitudinal and transverse times of the PC spin relaxation: T21; this condition is realized in solid bodies. The modulation ENDOR signal behaviour is studied in detail for F-centres in LiF
Luksic, Primoz; Pisanski, Tomaz
2006-01-01
If we are given a connected finite graph $G$ and a subset of its vertices $V_{0}$, we define a distance-residual graph as a graph induced on the set of vertices that have the maximal distance from $V_{0}$. Some properties and examples of distance-residual graphs of vertex-transitive, edge-transitive, bipartite and semisymmetric graphs are shown. The relations between the distance-residual graphs of product graphs and their factors are shown.
International Nuclear Information System (INIS)
The results of simulation of the propagation of optical signals in a multichannel high-bit-rate fibreoptic communication line with a combined scheme for amplifying optical signals based on new modulation data-transmission formats are presented. A comparative characteristic of formats with the amplitude and phase modulations of the electromagnetic-wave carrier is presented. The results of numerical simulation show that phase-modulation formats have a considerable advantage over amplitude formats. The use of phase-modulation formats leads to an increase in the maximum range of high-quality communications by a factor of three on average compared to amplitude-modulation formats. It is shown that optimal propagation regimes both in the case of amplitude-modulation and phase-modulation formats are realised for the normal (negative) group-velocity dispersion. However, the dispersion value for amplitude-modulation formats proves to be considerably greater than for phase-modulation formats. (optical communication)
An electronically addressed spatial light modulator
Mcknight, Douglas J.
1989-01-01
Coherent optical data processing is recognised to be a natural solution to certain information processing problems. Attempts to exploit the benefits of optical processing are limited by the quality of available Spatial Light Modulators. Spatial Light Modulators are devices which controllably impress information onto the amplitude or phase of an optical wavefront. They are used both to input data into an opticaI system and as modulating elements within the system (often in the Fourier plane...
On the Classification of Residues of the Grassmannian
Ashok, Sujay K
2010-01-01
We study leading singularities of scattering amplitudes which are obtained as residues of an integral over a Grassmannian manifold. We recursively do the transformation from twistors to momentum twistors and obtain an iterative formula for Yangian invariants that involves a succession of dualized twistor variables. This turns out to be useful in addressing the problem of classifying the residues of the Grassmannian. The iterative formula leads naturally to new coordinates on the Grassmannian in terms of which both composite and non-composite residues appear on an equal footing. We write down residue theorems in these new variables and classify the independent residues for some simple examples. These variables also explicitly exhibit the distinct solutions one expects to find for a given set of vanishing minors from Schubert calculus.
On the validity of mean-field amplitude equations for counterpropagating wavetrains
Pierce, R. D.; Wayne, C. E.
1994-01-01
We rigorously establish the validity of the equations describing the evolution of one-dimensional long wavelength modulations of counterpropagating wavetrains for a hyperbolic model equation, namely the sine-Gordon equation. We consider both periodic amplitude functions and localized wavepackets. For the localized case, the wavetrains are completely decoupled at leading order, while in the periodic case the amplitude equations take the form of mean-field (nonlocal) Schr\\"odi...
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...
Alphaspectroscopic amplitudes for nuclei in the lower half of the sd-shell
International Nuclear Information System (INIS)
Alpha-spectroscopic amplitudes and factors were calculated with the aid of the shell model for nuclei with mass numbers between A = 16 and A = 24. For transitions to levels belonging to the ground state band of the residual nucleus, the findings confirm the predictions based on the SU(3) model. (orig.)
Is the effect of tinnitus on auditory steady-state response amplitude mediated by attention?
Directory of Open Access Journals (Sweden)
EugenDiesch
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.
Ozcan, A.C.; A. Harmanci; Smith, P. F.
2006-01-01
Let R be a ring. An R-module M is called a (weak) duo module provided every (direct summand) submodule of M is fully invariant. It is proved that if R is a commutative domain with field of fractions K then a torsion-free uniform R-module is a duo module if and only if every element k in K such that kM is contained in M belongs to R. Moreover every non-zero finitely generated torsion-free duo R-module is uniform. In addition, if R is a Dedekind domain then a torsion R-module is a duo module...
Solitary Alfven wave envelopes and the modulational instability
International Nuclear Information System (INIS)
The derivative nonlinear Schroedinger equation describes the modulational instability of circularly polarized dispersive Alfven wave envelopes. It also may be used to determine the properties of finite amplitude localized stationary wave envelopes. Such envelope solitons exist only in conditions of modulational stability. This leaves open the question of whether, and if so, how, the modulational instability produces envelope solitons. 12 refs
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)
Perry, Gavin; Randle, James M; Koelewijn, Loes; Routley, Bethany C; Singh, Krish D
2015-01-01
Individual differences in the visual gamma (30-100Hz) response and their potential as trait markers of underlying physiology (particularly related to GABAergic inhibition) have become a matter of increasing interest in recent years. There is growing evidence, however, that properties of the gamma response (e.g., its amplitude and frequency) are highly stimulus dependent, and that individual differences in the gamma response may reflect individual differences in the stimulus tuning functions of gamma oscillations. Here, we measured the tuning functions of gamma amplitude and frequency to luminance contrast in eighteen participants using MEG. We used a grating stimulus in which stimulus contrast was modulated continuously over time. We found that both gamma amplitude and frequency were linearly modulated by stimulus contrast, but that the gain of this modulation (as reflected in the linear gradient) varied across individuals. We additionally observed a stimulus-induced response in the beta frequency range (10-25Hz), but neither the amplitude nor the frequency of this response was consistently modulated by the stimulus over time. Importantly, we did not find a correlation between the gain of the gamma-band amplitude and frequency tuning functions across individuals, suggesting that these may be independent traits driven by distinct neurophysiological processes. PMID:25906070
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.
Investigation of the maximum amplitude increase from the Benjamin-Feir instability
Karjanto, N; Peterson, P
2011-01-01
The Nonlinear Schr\\"odinger (NLS) equation is used to model surface waves in wave tanks of hydrodynamic laboratories. Analysis of the linearized NLS equation shows that its harmonic solutions with a small amplitude modulation have a tendency to grow exponentially due to the so-called Benjamin-Feir instability. To investigate this growth in detail, we relate the linearized solution of the NLS equation to a fully nonlinear, exact solution, called soliton on finite background. As a result, we find that in the range of instability the maximum amplitude increase is finite and can be at most three times the initial amplitude.
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)
International Nuclear Information System (INIS)
Measuring procedures for sensor parameters in frequency modulation dynamic force microscopy have been studied. As the tip-sample interaction forces cannot be recalculated from the experimental data without knowledge of the sensor's spring constant and oscillation amplitude, a treatment for normal spring constant calibration and newly developed schemes for the determination of the cantilever oscillation amplitude are presented. The amplitude evaluation techniques are based either on tunnelling current operation or frequency shift detection and are therefore applicable to many tip-sample systems. Although the amplitudes measured were larger than 1 nm, the scheme is applicable over a wide range of stable oscillation conditions, in particular for very small amplitudes. The ideas have been developed with the aid of simple calculations and simulations. Findings are supported by results from our low-temperature ultrahigh vacuum, dual-mode dynamic force and scanning tunnelling microscope. A quartz tuning fork has been used as a force sensor
New identities among gauge theory amplitudes
International Nuclear Information System (INIS)
Color-ordered amplitudes in gauge theories satisfy non-linear identities involving amplitude products of different helicity configurations. We consider the origin of such identities and connect them to the Kawai-Lewellen-Tye (KLT) relations between gravity and gauge theory amplitudes. Extensions are made to one-loop order of the full N=4 super Yang-Mills multiplet.
New Identities among Gauge Theory Amplitudes
Bjerrum-Bohr, N E J; Feng, Bo; Sondergaard, Thomas
2010-01-01
Color-ordered amplitudes in gauge theories satisfy non-linear identities involving amplitude products of different helicity configurations. We consider the origin of such identities and connect them to the Kawai-Lewellen-Tye (KLT) relations between gravity and gauge theory amplitudes. Extensions are made to one-loop order of the full N=4 super Yang-Mills multiplet.
Recursion relations, helicity amplitudes and dimensional regularization
International Nuclear Information System (INIS)
Using the method of on-shell recursion relations we compute tree level amplitudes including D-dimensional scalars and fermions. These tree level amplitudes are needed for calculations of one-loop amplitudes in QCD involving external quarks and gluons
Recursion relations, Helicity Amplitudes and Dimensional Regularization
Quigley, C; Quigley, Callum; Rozali, Moshe
2006-01-01
Using the method of on-shell recursion relations we compute tree level amplitudes including D-dimensional scalars and fermions. These tree level amplitudes are needed for calculations of one-loop amplitudes in QCD involving external quarks and gluons.
Factorization of bosonic string scattering amplitudes
International Nuclear Information System (INIS)
In an off-shell formulation, where scattering amplitudes for closed bosonic strings are defined as Polyakov path integrals over bordered world sheets, factorization of the amplitudes at the poles of exchanged particle states is shown in any order of perturbation theory. The same factorization is obtained for amplitudes defined via vertex operators, again for any number of loops. (orig.)
Poisson modules and degeneracy loci
Gualtieri, Marco
2012-01-01
In this paper, we study the interplay between modules and sub-objects in holomorphic Poisson geometry. In particular, we define a new notion of "residue" for a Poisson module, analogous to the Poincar\\'e residue of a meromorphic volume form. Of particular interest is the interaction between the residues of the canonical line bundle of a Poisson manifold and its degeneracy loci---where the rank of the Poisson structure drops. As an application, we provide new evidence in favour of Bondal's conjecture that the rank \\leq 2k locus of a Fano Poisson manifold always has dimension \\geq 2k+1. In particular, we show that the conjecture holds for Fano fourfolds. We also apply our techniques to a family of Poisson structures defined by Fe\\u{\\i}gin and Odesski\\u{\\i}, where the degeneracy loci are given by the secant varieties of elliptic normal curves.
Sodium cleaning in Phenix Steam Generator modules
International Nuclear Information System (INIS)
The repair of the PHENIX steam-generator's modules needed to establish a particular sodium cleaning procedure. The standard PHENIX cleaning procedure, using water vapour in presence of nitrogen and carbon dioxide was indeed not suitable, because of bulky sodium residues and specific geometry of modules. A specific procedure, using a gradual water vapour nitrogen process has been developed, qualified and industrially implemented in a very short delay, in order to clean efficiently the steam generators modules, before repair and requalification. (author)
Effect Of Phase Unbalance In Product Modulator
Nguyen, Tien M.
1992-01-01
Paper presents theoretical study of effect of phase unbalance in product modulator of phase-modulation transmitter in deep-space telemetry system upon performance of system. Mathematical model of product modulator used to derive equations for relative strengths of desired suppressed-carrier component and undesired residual-carrier component of transmitted signal. Also addresses effects of unsuppressed-carrier component on carrier-tracking phase-locked loop and bit detector in receiver.
Thiometon residues in cucumber
International Nuclear Information System (INIS)
In the Islamic Republic of Iran, vegetables are treated repeatedly with pesticides to control pests and diseases. Crops harvested shortly after pesticide application are probably contaminated by pesticides that are toxic to humans. Pesticide residues in vegetables are especially important, since these crops are ingested directly by humans. In recent years, farmers have been using more persistent pesticides to protect their crops because of increasing pesticide prices. Field trials were carried out to determine the residues of thiometon, a systemic insecticide used on cucumber. In 1993 and 1994, Ekatin (a 25% thiometon emulsifiable concentrate) was applied with a knapsack sprayer to cucumber (var. Daminus) at late flowering at dilutions of 1:1000 and 2:1000. Plots were 25 m2 in three replicates and were sampled 3, 6, 10, 15, 19 and 24 days after application. The samples were extracted with acetonitrile and cleanup was carried out using thin layer chromatography. Thiometon and two metabolites (thiometon sulphide and thiometon sulphone) were analyzed by gas chromatography. In 1994, the amount of thiometon sulphide determined 24 days treatment was 2 ppm in the peeled cucumber, which exceeded the maximum residue limit of 0.5 ppm. The total thiometon residues were higher in the peeled cucumber than those in the cucumber peel. Thus, peeling is ineffective for reducing the systemic residues of thiometon. Likewise, in this experiment lower dilution caused higher ratxperiment lower dilution caused higher rather than lower thiometon residues in cucumber. The rapid disappearance of thiometon residues 2 weeks after treatment suggests that storing cucumbers at room temperature may be a better strategy for reducing excessive thiometon residues. Alternatively, a contact insecticide could be used. Thus, the bulk of the surface residues could be removed by washing or peeling. (author). 5 refs, 4 figs
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.
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.
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).
Charles, Raphael
2004-01-01
This work is a contribution to the development of a specific method to assess the presence of residues in agricultural commodities. The following objectives are formulated: to identify and describe main processes in environment — plant exchanges, to build of a model to assess the residue concentration at harvest in agricultural commodities, to understand the functioning of the modelled system, to characterise pesticides used in field crops and identify optimisation potentials in phytosanitary...
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
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.
Thermodynamic properties of a magnetically modulated graphene
Islam, SK Firoz; Ghosh, Tarun Kanti
2011-01-01
The effect of magnetic modulation on thermodynamic properties of a graphene monolayer in presence of a constant perpendicular magnetic field is reported here. One-dimensional spatial electric or magnetic modulation lifts the degeneracy of the Landau levels and converts into bands and their band width oscillates with magnetic field leading to Weiss-type oscillation in the thermodynamic properties. The effect of magnetic modulation on thermodynamic properties of a graphene sheet is studied and then compared with electrically modulated graphene and magnetically modulated conventional two-dimensional electron gas (2DEG). We observe Weiss-type and de Haas-van Alphen (dHvA) oscillations at low and high magnetic field, respectively. There is a definite phase difference in Weiss-type oscillations in thermodynamic quantities of magnetically modulated graphene in compare to electrically modulated graphene. On the other hand, the phase remains same and amplitude of the oscillation is large when compared with the magneti...
Phase ramping and modulation of reflectometer signals
International Nuclear Information System (INIS)
The phase and amplitude signals of JET heterodyne reflectometers show varying levels of high frequency turbulence superimposed on a slow changing mean. The phase signal also shows multi-radian (> 1 fringe) variations with two quite different time scales (2-10 ms and sub-ms). In both cases the mean reflected power, together with turbulent phase and amplitude fluctuation levels, are modulated synchronously with the are modulated synchronously with the phase fringes. The slow fringes appear to result radial movement of the cutoff layer with the amplitude modulation possibly due to multiple reflection between plasma and wall. The fast fringes occur in intermittent bursts and appear to be phase runaway resulting from antenna misalignment. Using a 2-D physical optics simulation code it is possible to replicate the fast bursts of phase runaway from steady-state turbulence and misaligned antennas. This offers a possible alternative explanation for some of the observations of bursting turbulence seen in reflectometer signals. (authors)
Vibrational amplitudes in vitreous silica
International Nuclear Information System (INIS)
A model structure of vitreous silica, for which the vibrational frequencies and eigenmodes were calculated from first principles, is used to investigate vibrational amplitudes. Calculated mean-square displacements for oxygen and silicon atoms are obtained as a function of temperature. The square displacement tensors of oxygen atoms show a marked anisotropic character, which is related to the local geometry. The displacements of oxygen atoms along the three principal directions can be associated to distinct parts of the vibrational spectrum, as evidenced by their thermal dependence. These anisotropic effects directly affect the elastic and the static structure factors, which are sensitive to the correlation between displacements of different atoms along their connecting direction. This description shows that the observed widths for Si-O and O-O correlations mainly derive from atomic vibrations rather than from structural disorder. Anisotropic correlations between different atoms are shown to be important up to a distance of 4 A, i.e., involving atoms that belong to corner-sharing tetrahedra. The scattering functions, calculated at finite temperature and in the harmonic approximation, show good agreement with experiment. In particular, the comparison between the static and the elastic structure factors yields a characterization of the correlated displacements in accord with experimental observations. The static structure factor is significantly affected by anisotropic cis significantly affected by anisotropic correlations, but shows only a weak dependence on temperature between 0 and 300 K
DETERMINISTIC COMPONENTS IN THE LIGHT CURVE AMPLITUDE OF Y OPH
International Nuclear Information System (INIS)
About two decades after the discovery of the amplitude decline of the light curve of the classical Cepheid Y Oph, its study is resumed using an increased amount of homogenized data and an extended time base. In our approach, the investigation of different time series concerning the light curve amplitude of Y Oph is not only the reason for the present study, but also a stimulus for developing a coherent methodology for studying long- and short-term variability phenomena in variable stars, taking into account the details of concrete observing conditions: amount of data, data sampling, time base, and individual errors of observational data. The statistical significance of this decreasing trend was estimated by assuming its linearity. We approached the decision-making process by formulating adequate null and alternative hypotheses, and testing the value of the regression line slope for different data sets via Monte Carlo simulations. A variability analysis, through various methods, of the original data and of the residuals obtained after removing the linear trend was performed. We also proposed a new statistical test, based on amplitude spectrum analysis and Monte Carlo simulations, intended to evaluate how detectible is a given (linear) trend in well-defined observing conditions: the trend detection probability. The main conclusion of our study on Y Oph is that, even if the false alarm probability is low enough to consider the decreasing trend to be statistically significreasing trend to be statistically significant, the available data do not allow us to obtain a reasonably powerful test. We are able to confirm the light curve amplitude decline, and the order of magnitude of its slope with a better statistical substantiation. According to the obtained values of the trend detection probability, it seems that the trend we are dealing with is marked by a low detectibility. Our attempt to find signs of possible variability phenomena at shorter timescales ended by emphasizing the relative constancy of our data, within their precision limits.
Excitation of spin echo by pulses with linear frequency modulation
Baruzdin, S. A.
2015-03-01
The excitation of a spin echo by two pulses with linear frequency modulation, upon which the pulse parameters ensure maximal compression of the response in time, is considered. The frequency of the excitation pulses was changed by a step law, approximating its linear rise. The transfer matrix of the state of the spin system for pulses with linear frequency modulation is found by solving the Bloch equations. The shape of the envelope of the spin echo in thin magnetic cobalt films, as well as the dependence of the echo amplitude on the parameters of the excitation pulses, is determined. The amplitudes of the excitation pulses, which ensure the excitation of the echo maximal amplitude for various values of the frequency deviation, are found. It is shown that the use of pulses with linear frequency modulation makes it possible to obtain the same echo amplitude as with the use of simple excitation pulses for a substantially smaller amplitude and power of excitation pulses.
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.
Veneziano Amplitudes, Spin Chains and String Models
Kholodenko, Arkady L
2008-01-01
In a series of recently published papers we reanalyzed the existing treatments of Veneziano and Veneziano-like amplitudes and the models associated with these amplitudes. In this work we demonstrate that the already obtained new partition function for these amplitudes can be exactly mapped into that for the Polychronakos-Frahm (P-F) spin chain model. This observation allows us to recover many of the existing string-theoretic models, including the most recent ones.
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
Global Residues and Two-Loop Hepta-Cuts
Sogaard, Mads
2013-01-01
We derive remarkably compact analytic expressions for coefficients of master integrals with two-loop crossed box topology in four-point gauge theory amplitudes with arbitrary adjoint matter and massless kinematics, thereby providing additional steps towards automated computation of the full amplitude. The coefficients are uniquely obtained by assembling residues extracted through integration on linear combinations of higher-dimensional tori encircling global poles of the loop integrand. Several explicit calculations are provided. We also establish exact equivalence of our results and master integral coefficients recently obtained via integrand-level reduction in any renormalizable gauge theory.
Obliquity Modulation of the Incoming Solar Radiation
Liu, Han-Shou; Smith, David E. (Technical Monitor)
2001-01-01
Based on a basic principle of orbital resonance, we have identified a huge deficit of solar radiation induced by the combined amplitude and frequency modulation of the Earth's obliquity as possibly the causal mechanism for ice age glaciation. Including this modulation effect on solar radiation, we have performed model simulations of climate change for the past 2 million years. Simulation results show that: (1) For the past 1 million years, temperature fluctuation cycles were dominated by a 100-Kyr period due to amplitude-frequency resonance effect of the obliquity; (2) From 2 to 1 million years ago, the amplitude-frequency interactions. of the obliquity were so weak that they were not able to stimulate a resonance effect on solar radiation; (3) Amplitude and frequency modulation analysis on solar radiation provides a series of resonance in the incoming solar radiation which may shift the glaciation cycles from 41-Kyr to 100-Kyr about 0.9 million years ago. These results are in good agreement with the marine and continental paleoclimate records. Thus, the proposed climate response to the combined amplitude and frequency modulation of the Earth's obliquity may be the key to understanding the glaciation puzzles in paleoclimatology.
Klagyivik, Peter
2009-01-01
Aims: We attempt to revise the period-amplitude (P-A) relationship of Galactic Cepheids based on multi-colour photometric and radial velocity data. Reliable P-A graphs for Galactic Cepheids constructed for the U, B, V, R_C, and I_C photometric bands and pulsational radial velocity variations facilitate investigations of previously poorly studied interrelations between observable amplitudes. The effects of both binarity and metallicity on the observed amplitude, and the dichotomy between short- and long-period Cepheids can both be studied. Results: Large amplitude Cepheids with companions exhibit smaller photometric amplitudes on average than solitary ones, as expected, while s-Cepheids pulsate with an rbitrary (although small) amplitude. The ratio of the observed radial velocity to blue photometric amplitudes, A_V_RAD/A_B, is not as good an indicator of the ulsation mode as predicted theoretically. This may be caused by an incorrect mode assignment to a number of small amplitude Cepheids, which are not ecessa...
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...
Modulated rotating convection: radially travelling concentric rolls
Rubio, A.; Lopez, J. M.; Marques, F.
Recent experiments in rotating convection have shown that the spatio-temporal bulk convective state with KLortz dynamics can be suppressed by small-amplitude modulations of the rotation rate. The resultant axisymmetric pulsed target patterns were observed to develop into axisymmetric travelling target patterns as the modulation amplitude and Rayleigh number were increased. Using the NavierBoussinesq equations with physical boundary conditions, we are able to numerically reproduce the experimental results and gain physical insight into the responsible mechanism, relating the onset of the travelling target patterns to a symmetry-restoring saddle-node on an invariant circle bifurcation. Movies are available with the online version of the paper.
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 pollul the dangerous waste, like sharp or polluted materials. In this way, an appreciable reduction is guaranteed in the impact on the atmosphere. (Author)
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).
International Nuclear Information System (INIS)
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)
Modulation masking produced by second-order modulators
DEFF Research Database (Denmark)
Füllgrabe, Christian; Moore, Brian C.J.
2005-01-01
Recent studies suggest that an auditory nonlinearity converts second-order sinusoidal amplitude modulation (SAM) (i.e., modulation of SAM depth) into a first-order SAM component, which contributes to the perception of second-order SAM. However, conversion may also occur in other ways such as cochlear filtering. The present experiments explored the source of the first-order SAM component by investigating the ability to detect a 5-Hz, first-order SAM probe in the presence of a second-order SAM masker beating at the probe frequency. Detection performance was measured as a function of masker-carrier modulation frequency, phase relationship between the probe and masker modulator, and probe modulation depth. In experiment 1, the carrier was a 5-kHz sinusoid presented either alone or within a notched-noise masker in order to restrict off-frequency listening. In experiment 2, the carrier was a white noise. The data obtained in both carrier conditions are consistent with the existence of a modulation distortion component. However, the phase yielding poorest detection performance varied across experimental conditions between 0° and 180°, confirming that, in addition to nonlinear mechanisms, cochlear filtering and off-frequency listening play a role in second-order SAM perception. The estimated magnitude of the modulation distortion component ranges from 5%–12%. ©2005 Acoustical Society of America.
Amplitude regeneration of RZ-DPSK signals in single-pump fiber-optic parametric amplifiers
DEFF Research Database (Denmark)
Peucheret, Christophe; Lorenzen, Michael Rodas
2009-01-01
The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ ON–OFF keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation.
Modulation transfer spectroscopy in atomic rubidium
International Nuclear Information System (INIS)
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 peak amplitude was increased by a factor of 2. The modulation transfer signal for the 85Rb F = 2 ? F' transitions is also presented to highlight how this technique can generate a single, clear line for laser frequency stabilization even in cases where there are a number of closely spaced hyperfine transitions
Six-Photon Amplitudes in Scalar QED
Bernicot, C
2008-01-01
The analytical result for the six-photon helicity amplitudes in scalar QED is presented. To compute the loop, a recently developed method based on multiple cuts is used. The amplitudes for QED and $QED^{\\caln=1}$ are also derived using the supersymmetric decomposition linking the three theories.
Six-photon amplitudes in scalar QED
International Nuclear Information System (INIS)
The analytical result for the six-photon helicity amplitudes in scalar QED is presented. To compute the loop, a recently developed method based on multiple cuts is used. The amplitudes for QED and QEDN=1 are also derived using the supersymmetric decomposition linking the three theories
Six-Photon Amplitudes in Scalar QED
Bernicot, C.; Guillet, J. -ph
2007-01-01
The analytical result for the six-photon helicity amplitudes in scalar QED is presented. To compute the loop, a recently developed method based on multiple cuts is used. The amplitudes for QED and $QED^{\\caln=1}$ are also derived using the supersymmetric decomposition linking the three theories.
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.
The Lorentzian proper vertex amplitude: Asymptotics
Engle, Jonathan; Zipfel, Antonia
2015-01-01
In previous work, the Lorentzian proper vertex amplitude for a spin-foam model of quantum gravity was derived. In the present work, the asymptotics of this amplitude are studied in the semi-classical limit. The starting point of the analysis is an expression for the amplitude as an action integral with action differing from that in the EPRL case by an extra `projector' term which scales linearly with spins only in the asymptotic limit. New tools are introduced to generalize stationary phase methods to this case. For the case of boundary data which can be glued to a non-degenerate Lorentzian 4-simplex, the asymptotic limit of the amplitude is shown to equal the single Feynman term, showing that the extra term in the asymptotics of the EPRL amplitude has been eliminated.
International Nuclear Information System (INIS)
The forest products industry is the third largest economic sector in Alberta, producing pulp and paper, dimensional lumber, paneling, and value added products, providing some 40,000 jobs . 'Value added' is a key component of expanding economic activity within the forest products sector. Wood residues can play a key role in obtaining more value from forest resources by providing new products, serving as feedstock to energy and chemical production, and playing a role in agriculture and land reclamation. One of the principal roles of the Forest Products Development Branch of the Alberta Economics Department is to encourage the development of the industry by creating new uses for these materials and developing awareness of the scope of the resource. Distances to markets, economic competition from conventional energy sources and coordination of research efforts are substantial barriers to further development that the Forest Products Development Branch has to face daily. Some notable successes in recent years are described. These include the Wood Residue Inventory and the Wood Residue Database that provide data on availability and principal location of wood residues, also a listing of contacts at the mills who produce the materials
Parton content of the nucleon from distribution amplitudes and transition distribution amplitudes
Pasquini, B.; Pincetti, M.; Boffi, S.
2009-01-01
The nucleon distribution amplitudes and the nucleon-to-pion transition distribution amplitudes are investigated at leading twist within the frame of a light-cone quark model. The distribution amplitudes probe the three-quark component of the nucleon light-cone wave function, while higher order components in the Fock-space expansion of the nucleon state are essential to describe the nucleon-to-pion transition distribution amplitudes. Adopting a meson-cloud model of the nucleo...
Electronic structure of magnetically modulated graphene
Sabeeh, K.; Tahir, M.; Mackinnon, A.
2008-01-01
We present a theoretical study of the electronic structure of magnetically modulated graphene. We consider monolayer graphene in the presence of a perpendicular magnetic field and a unidirectional weak magnetic modulation. The density of states and the bandwidth of the Dirac electrons in this system are determined. We have found magnetic Weiss oscillations in the bandwidth and the density of states. These oscillations are out of phase and larger in amplitude than the ones in...
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.
Saat, N. K.; Dean, P.; Khanna, S. P.; Salih, M.; Linfield, E. H.; Davies, A. G.
2015-04-01
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.
PWR plant model for the analysis of large amplitude transients
International Nuclear Information System (INIS)
The PWR transient code ALMOD has been developed to cover a wide range of transient and accident simulation in safety analysis, comprising failure of safety system components (e.g., analysis of anticipated transients without scram = ATWS). Because of the large amplitudes to be expected during the transients, simplified models such as linearized models, used in control system analysis, are not applicable here. As the transients have to be analyzed over minutes, feedback from the entire coolant system becomes effective, thus requiring the simulation of core and both primary and secondary coolant systems. Because of the long duration of the transients special emphasis has been put on computational speed. Key variables of interest in transient analysis are fuel and cladding temperature as well as primary and secondary system pressure. Extreme plant conditions such as two-phase flow in the primary coolant system, filling of the pressurizer with water etc., have to be simulated with sufficient accuracy. The PWR plant model ALMOD comprises reactor core, primary coolant system, pressurizer, steam generator and steam dump system as well as important components of the safety and control system. The code has a modular structure with the main modules being neutron kinetics, fuel thermodynamics, primary coolant system, pressurizer, steam generator and safety system. Most modules can be operated as independent programs. For some modules two versions are available with different degrversions are available with different degrees of accuracy
Sensitive behavior of 2???-decay amplitude within QRPA and broken SU(4) symmetry in nuclei
International Nuclear Information System (INIS)
Making use of an identity transformation independent of a nuclear model, we represent the 2???-amplitude as a sum of two terms. One term accounts for most of the sensitivity of the original 2???-amplitude to gpp' for realistic gpp'?1 (with gpp' being the ratio of the triplet and singlet p-p interaction strengths) and is determined by a specific energy-weighted sum rule. The sum rule depends only on the particle-particle residual interaction (being linear function of gpp' in the QRPA) and passes through zero at the point gpp'=1 where the Wigner SU(4) symmetry is restored in the p-p sector of the Hamiltonian. The second term in the decomposition of the 2???-amplitude is demonstrated within the QRPA to be a much smoother function for the realistic values of gpp' than the original 2???-amplitude. This term is mainly determined by the intensity of the spin-orbit interaction of the nuclear mean field. Thus, the analysis of the present work reveals the reasons for the sensitivity of the 2???-amplitude to different components of the nuclear Hamiltonian and thereby can help in constraining nuclear model uncertainties in calculations of the amplitude
Xiangbin Yu; Xiaomin Chen; Yuyu Xin; Qiuming Zhu; Dazhuan Xu
2012-01-01
Differential space-time coding (DSTC) technique has become a good choice when channel estimations are difficult to obtain in multiple antennas system. On the basis of analyzing the existing DSTC schemes, by introducing multi-level quadrature amplitude modulation (MQAM) and matrix transform method, we develop a multi-amplitude differential space-time block coding (STBC) scheme for square or non-square code matrix in MIMO systems, and give the derivation of calculation formulae of the coding ad...
Relativistic amplitudes in terms of wave functions
International Nuclear Information System (INIS)
In the framework of the invariant diagram technique which arises at the formulation of the fueld theory on the light front the question about conditions at which the relativistic amplitudes may be expressed through the wave functions is investigated. The amplitudes obtained depend on four-vector ?, determining the light front surface. The way is shown to find such values of the four-vector ?, at which the contribution of diagrams not expressed through wave functions is minimal. The investigation carried out is equivalent to the study of the dependence of amplitudes of the old-fashioned perturbation theory in the in the infinite momentum frame on direction of the infinite momentum
Amplitude death with mean-field diffusion
Sharma, Amit; Shrimali, Manish Dev
2012-05-01
We study the dynamics of nonlinear oscillators under mean-field diffusive coupling. We observe that this form of coupling leads to amplitude death via a synchronization transition in the parameter space of the coupling strength and mean-field control parameter. A general criterion for amplitude death for any given dynamical system with mean-field diffusion is obtained, and these dynamical transitions are characterized using various indices such as average phase difference, Lyapunov exponents, and average amplitude. This behavior is analyzed in the parameter plane by numerical studies of specific cases of the Landau-Stuart limit-cycle oscillator, and Rössler, Lorenz, FitzHugh-Nagumo excitable, and Chua systems.
Modulated ECCD experiments on TCV
International Nuclear Information System (INIS)
Experiments were previously performed on TCV using Switched Electron Cyclotron Current Drive (SECCD) in which the total heating power and plasma current were kept nearly constant in time while the current density profile was modulated. It was observed that SECCD leads to relative electron diffusivity modulation amplitude of ±65%. A direct measurement of the current density profile is not available on TCV; however, electrodynamics calculations show that ±55% shear modulation (from s = 0.20 to 0.70) is achieved during SECCD experiments, and that the shear modulation is localized at the CD layer position. These results provide strong experimental evidence that electron heat transport is shearing dependent: heat transport is reduced when shear is low, confirming a general observation. New experiments have been performed to address some open issues raised after the previous campaign. The work is also aimed at confirmation of the electrodynamics model of the SECCD technique. To these ends, the experiments have been performed at different deposition radii, different SECCD amplitudes and different toroidal injection angles. It turned out that in most discharges an MHD activity develops, differentiated in the co and counter injection phases, which prevents an unambiguous conclusion in terms of heat or particle transport. It is shown that the MHD modes are affected by ECCD on the resonant magnetic surfaces, possibly according to the same physics underlying TM and NTM stabilize physics underlying TM and NTM stabilization process. Data analysis from this point of view is in progress. (author)
Tewari, Krishna C. (Whitehall, PA); Foster, Edward P. (Macungie, PA)
1985-01-01
Coal solids (SRC) and distillate oils are combined to afford single-phase blends of residual oils which have utility as fuel oils substitutes. The components are combined on the basis of their respective polarities, that is, on the basis of their heteroatom content, to assure complete solubilization of SRC. The resulting composition is a fuel oil blend which retains its stability and homogeneity over the long term.
Is the effect of tinnitus on auditory steady-state response amplitude mediated by attention?
Diesch, Eugen; Andermann, Martin; Rupp, Andre
2012-01-01
Objectives: Auditory steady-state response (ASSR) amplitude enhancement effects have been reported in tinnitus patients. As ASSR amplitude is also enhanced by attention, the effect of tinnitus on ASSR amplitude could be interpreted as an effect of attention mediated by tinnitus. As N1 attention effects are significantly 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 which were previously examined for the ASSR (Diesch et al., 2010a) were analyzed with respect to the N1m component. Like the ASSR previously, the N1m was analyzed in the source domain (source space projection). Stimuli were amplitude-modulated (AM) tones with one of three carrier frequencies matching the tinnitus frequency or a surrogate frequency 1½ octave above the audiometric edge frequency in controls, the audiometric edge frequency, and a frequency below the audiometric edge. Single AM-tones were presented in a single condition and superpositions of three AM-tones differing in carrier and modulation frequency in a composite condition. Results: In the earlier ASSR study (Diesch et al., 2010a), the ASSR amplitude in tinnitus patients, but not in controls, was significantly larger in the (surrogate) tinnitus condition than in the edge condition. Patients showed less evidence than controls of reciprocal inhibition of component ASSR responses in the composite condition. In the present study, N1m amplitudes elicited by stimuli located at the audiometric edge and at the (surrogate) tinnitus frequency were smaller than N1m amplitudes elicited by sub-edge tones both in patients and controls. The relationship of the N1m response in the composite condition to the N1m response in the single condition indicated that reciprocal inhibition among component N1m responses was reduced in patients compared against controls. Conclusions: In the present study, no evidence was found for an N1-amplitude enhancement effect in tinnitus. Compared to controls, reciprocal inhibition is reduced in tinnitus patients. Thus, as there is no effect on N1m that could potentially be attributed to attention, it seems unlikely that the enhancement effect of tinnitus on ASSR amplitude could be accounted for in terms of attention induced by tinnitus. PMID:22661932
High-performance optical modulators based on stepped quantum wells
Mohseni, H.; Chan, W. K.; An, H.; Ulmer, A.; Capewell, D.
2006-02-01
High-speed and high-performance optical phase and amplitude modulators are critical components of many photonic systems. Semiconductor-based modulators are very attractive, since they can be monolithically integrated with other semiconductor devices. Unfortunately, the commonly used modulators based on square quantum wells have inherent properties that limit their modulation performance. We present a new class of quantum wells called "stepped quantum wells" (SQW) with extra degrees of freedom that can be used to design high performance optical modulators. We demonstrated SQW phase modulators with nearly one order of magnitude higher efficiency than their counterparts. Also, linearized modulators based on SQW with more than two orders of magnitude higher linearity than the existing semiconductor modulators are presented. Finally, high-performance surface-normal modulators based on SQWs with nearly two times better efficiency and 7 dB higher extinction ratio compared with the conventional devices with rectangular and coupled-quantum well active layers are demonstrated.
Homological invariants of modules over contracting endomorphisms
Avramov, Luchezar L.; Hochster, Melvin; Iyengar, Srikanth B.; Yao, Yongwei
2010-01-01
It is proved that when R is a local ring of positive characteristic, $\\phi$ is its Frobenius endomorphism, and some non-zero finite R-module has finite flat dimension or finite injective dimension for the R-module structure induced through $\\phi$, then R is regular. This broad generalization of Kunz's characterization of regularity in positive characteristic is deduced from a theorem concerning a local ring R with residue field of k of arbitrary characteristic: If $\\phi$ is ...
Grassmannians for scattering amplitudes in 4d $\\mathcal{N}=4$ SYM and 3d ABJM
Elvang, Henriette; Keeler, Cynthia; Lam, Thomas; Olson, Timothy M; Roland, Samuel B; Speyer, David E
2014-01-01
Scattering amplitudes in 4d $\\mathcal{N}=4$ super Yang-Mills theory (SYM) can be described by Grassmannian contour integrals whose form depends on whether the external data is encoded in momentum space, twistor space, or momentum twistor space. After a pedagogical review, we present a new, streamlined proof of the equivalence of the three integral formulations. A similar strategy allows us to derive a new Grassmannian integral for 3d $\\mathcal{N}=6$ ABJM theory amplitudes in momentum twistor space: it is a contour integral in an orthogonal Grassmannian with the novel property that the internal metric depends on the external data. The result can be viewed as a central step towards developing an amplituhedron formulation for ABJM amplitudes. Various properties of Grassmannian integrals are examined, including boundary properties, pole structure, and a homological interpretation of the global residue theorems for $\\mathcal{N}=4$ SYM.
Methods and devices for optimizing the operation of a semiconductor optical modulator
Energy Technology Data Exchange (ETDEWEB)
Zortman, William A.
2015-07-14
A semiconductor-based optical modulator includes a control loop to control and optimize the modulator's operation for relatively high data rates (above 1 GHz) and/or relatively high voltage levels. Both the amplitude of the modulator's driving voltage and the bias of the driving voltage may be adjusted using the control loop. Such adjustments help to optimize the operation of the modulator by reducing the number of errors present in a modulated data stream.
Amplitude Variations in Pulsating Yellow Supergiants
Percy, John R
2014-01-01
It was recently discovered that the amplitudes of pulsating red giants and supergiants vary significantly on time scales of 20-30 pulsation periods. Here, we analyze the amplitude variability in 29 pulsating yellow supergiants (5 RVa, 4 RVb, 9 SRd, 7 long-period Cepheid, and 4 yellow hypergiant stars), using visual observations from the AAVSO International Database, and Fourier and wavelet analysis using the AAVSO's VSTAR package. We find that these stars vary in amplitude by factors of up to 10 or more (but more typically 3-5), on a mean time scale (L) of 33 +/- 4 pulsation periods (P). Each of the five sub-types shows this same behavior, which is very similar to that of the pulsating red giants, for which the median L/P was 31. For the RVb stars, the lengths of the cycles of amplitude variability are the same as the long secondary periods, to within the uncertainty of each.
String Scattering Amplitudes in High Energy Limits
Yang, Yi; Lee, Jenchi
2011-01-01
A very review of string scattering amplitudes in two important high energy limits: hard scattering and Regge scattering. Recent results of the symmetries in string theory by studying high energy string scattering anplitudes are showed.
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.
Motivic multiple zeta values and superstring amplitudes
International Nuclear Information System (INIS)
The structure of tree-level open and closed superstring amplitudes is analyzed. For the open superstring amplitude we find a striking and elegant form, which allows one to disentangle its ??-expansion into several contributions accounting for different classes of multiple zeta values. This form is bolstered by the decomposition of motivic multiple zeta values, i.e. the latter encapsulate the ??-expansion of the superstring amplitude. Moreover, a morphism induced by the coproduct maps the ??-expansion onto a non-commutative Hopf algebra. This map represents a generalization of the symbol of a transcendental function. In terms of elements of this Hopf algebra the ??-expansion assumes a very simple and symmetric form, which carries all the relevant information. Equipped with these results we can also cast the closed superstring amplitude into a very elegant form. (paper)
Open String Amplitudes in Various Gauges
Fuji, H; Suzuki, H; Fuji, Hiroyuki; Nakayama, Shinsaku; Suzuki, Hisao
2007-01-01
Recently, Schnabl constructed the analytic solution of the open string tachyon. Subsequently, the absence of the physical states at the vacuum was proved. The development relies heavily on the use of the gauge condition different from the ordinary one. It was shown that the choice of gauge simplifies the analysis drastically. When we perform the calculation of the amplitudes in Schnabl gauge, we find that the off-shell amplitudes of the Schnabl gauge is still very complicated. In this paper, we propose the use of the propagator in the modified Schnabl gauge and show that this modified use of the Schnabl gauge simplifies the computation of the off-shell amplitudes drastically. We also compute the amplitudes of open superstring in this gauge.
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
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.)
Antenna Factorization of Gauge-Theory Amplitudes
Kosower, D A
1998-01-01
I derive a single factorization formula which summarizes all soft and collinear divergences of a tree-level gauge theory amplitude. The singular factor squared is in a certain sense the generalization of the Catani--Seymour dipole factorization formula.
Antenna Factorization of Gauge-Theory Amplitudes
Kosower, David A.
1997-01-01
I derive a single factorization formula which summarizes all soft and collinear divergences of a tree-level gauge theory amplitude. The singular factor squared is in a certain sense the generalization of the Catani-Seymour dipole factorization formula.
REMOTE SENSING CROP RESIDUE COVER
Current methods of quantifying crop residue cover are inadequate for characterizing the spatial variability of residue cover within fields or across large regions. Our objectives were to evaluate several spectral indices for measuring crop residue cover using satellite hyperspectral data and to cate...
[Role of ocular pulse amplitude in glaucoma].
Stürmer, J P E; Kniestedt, C
2015-02-01
The ocular pulse amplitude is defined as the difference between diastolic and systolic intraocular pressure. The ocular pulse is generated by the pulsatile ocular blood flow in the choroid. It is dependent on the dynamics of the cardiovascular system, the rigidity of the ocular vessels on one side and the biomechanical properties of the eye on the other side. In addition the influence of outflow facility of the aqueous humor, the level of the intraocular pressure itself and last but not least the rigidity of the sclera on the ocular pulse amplitude is until now not clear. Dynamic contour tonometry (Pascal®) does not only measure intraocular pressure almost independent of corneal thickness and curvature but also allows easy and fast measurement of ocular pulse amplitude on the slit lamp. The ocular pulse amplitude in healthy subjects is between 1.2 and 4?mmHg. If the ocular pulse amplitude is larger than 1.2?mmHg spontaneous pulsations of the central retinal vein are visible on fundoscopy. In patients with ocular hypertension the ocular pulse amplitude is larger than in normal subjects but this is mainly due to higher IOP levels. In patients with manifest open-angle glaucoma the ocular pulse amplitude stays initially within the normal range. In more advanced stages of the disease and especially in patients with ocular perfusion pressure dependent optic neuropathy the ocular pulse amplitude is gradually reduced. Due to the various factors influencing ocular pulse amplitude a direct correlation between reduced ocular pulse amplitude and reduced ocular perfusion pressure has not been established as yet. New approaches investigating the variations of the ocular pressure Fourier spectral analysis are promising, especially when simultaneous analysis of the arterial blood pressure is performed. These techniques may allow a fast and easy discrimination between healthy and glaucomatous patients in the near future. If ocular pulse amplitude exhibits a massive inter-ocular asymmetry in the presence of symmetrical ocular findings of extraocular vascular pathologies (i.e. carotid stenosis) are the most likely cause and therefore should be excluded. PMID:25700254
Amplitudes for Higgs Bosons plus Four Partons
Kauffman, Russel P.; Desai, Satish V.; Risal, Dipesh
1999-01-01
In this talk we consider amplitudes for processes involving a Higgs boson, either scalar or pseudoscalar, plus four light partons. These amplitudes are relevant to the production of a Higgs boson plus two jets in hadronic collisions. They are also relevant to calculating the transverse momentum spectrum for Higgs bosons at next-to-leading order in the strong coupling. We work in the limit that the top quark is much heavier than the Higgs bosons and use effective Lagrangians ...
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.)
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.
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)
Getting superstring amplitudes by degenerating Riemann surfaces
Matone, Marco; Volpato, Roberto(Max-Planck-Institut für Gravitationsphysik, Am Mühlenberg 1, D-14476, Golm, Germany)
2010-01-01
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...
Meson mixing amplitudes in asymmetric nuclear matter
Mori, Yoshiharu; Saito, Koichi
2002-01-01
Using a purely hadronic model, we study the charge-symmetry-breaking $\\rho$-$\\omega$, $\\sigma$-$\\delta$, $\\sigma$-$\\rho$ and $\\delta$-$\\omega$ mixing amplitudes in isospin asymmetric nuclear matter. The basic assumption of the model is that the mixing amplitude is generated by nucleon and anti-nucleon loops and hence driven entirely by the difference between proton and neutron Fermi momenta and the proton-neutron mass difference. We find that the behavior of the mixing ampli...
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)
Protecting quantum entanglement from amplitude damping
Liao, Zeyang; Al-amri, M.; Zubairy, M. Suhail
2012-01-01
Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently stu...
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)
Relations between closed string amplitudes at higher-order tree level and open string amplitudes
International Nuclear Information System (INIS)
KLT relations almost factorize closed string amplitudes on S2 by two open string tree amplitudes which correspond to the left- and the right-moving sectors. In this paper, we investigate string amplitudes on D2 and RP2. We find that KLT factorization relations do not hold in these two cases. The relations between closed and open string amplitudes have new forms. On D2 and RP2, the left- and the right-moving sectors are connected into a single sector. Then an amplitude with closed strings on D2 or RP2 can be given by one open string tree amplitude except for a phase factor. The relations depends on the topologies of the world-sheets. Under T-duality, the relations on D2 and RP2 give the amplitudes between closed strings scattering from D-brane and O-plane respectively by open string partial amplitudes. In the low energy limits of these two cases, the factorization relations for graviton amplitudes do not hold. The amplitudes for gravitons must be given by the new relations instead.
Displaced phase-amplitude variables for waves on finite background
International Nuclear Information System (INIS)
Wave amplification in nonlinear dispersive wave equations may be caused by nonlinear focussing of waves from a certain background. In the model of nonlinear Schroedinger equation we will introduce a transformation to displaced phase-amplitude variables with respect to a background of monochromatic waves. The potential energy in the Hamiltonian then depends essentially on the phase. Looking as a special case to phases that are time independent, the oscillator equation for the signal at each position becomes autonomous, with the change of phase with position as only driving force for a spatial evolution towards extreme waves. This is observed to be the governing process of wave amplification in classes of already known solutions of NLS, namely the Akhmediev-, Ma- and Peregrine-solitons. We investigate the case of the soliton on finite background in detail in this Letter as the solution that describes the complete spatial evolution of modulational instability from background to extreme waves
Banjo timbre from string stretching and frequency modulation
Politzer, David
2014-01-01
The geometry of a floating bridge on a drumhead soundboard produces string stretching that is first order in the amplitude of the bridge motion. This stretching modulates the string tension and consequently modulates string frequencies at acoustic frequencies. Early work in electronic sound synthesis identified such modulation as a source of bell-like and metallic timbre. And increasing string stretching by adjusting banjo string-tailpiece-head geometry is known to enhance c...
Calibration of the LIGO displacement actuators via laser frequency modulation
Goetz, E.; Savage Jr, R. L.
2010-01-01
We present a frequency modulation technique for calibration of the displacement actuators of the LIGO 4-km-long interferometric gravitational-wave detectors. With the interferometer locked in a single-arm configuration, we modulate the frequency of the laser light, creating an effective length variation that we calibrate by measuring the amplitude of the frequency modulation. By simultaneously driving the voice coil actuators that control the length of the arm cavity, we cal...
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 clinicaxes or underestimated due to unmet clinical (voltage) criteria, or occur in ECG components that are not regularly examined
Use of the delta-t method for setting rf phase and amplitude for the AHF linac
International Nuclear Information System (INIS)
The delta-t procedure is a time-of-flight method of finding set points for the rf phase and amplitude for each module of a linac. Expected errors for LAMPF afterburner linacs which might be used for an advanced hadron facility (AHF) are calculated. The modified delta-t procedure used on modules 13 through 48 of the present linac appears adequate to set up the proposed AHF linacs. 24 refs., 7 figs., 1 tab
Testing the dipole modulation model in CMBR
International Nuclear Information System (INIS)
The hemispherical power asymmetry, observed in the CMBR data, has generally been interpreted in terms of the dipole modulation model for the temperature fluctuations. Here we point out that this model leads to several predictions, which can be directly tested in the current data. We suggest tests of the hemispherical power asymmetry both in real and multipole space. We find a significant signal of the dipole modulation model in WMAP and PLANCK data with our tests. The dipole amplitude and direction also agrees, within errors, with earlier results based on hemispherical analysis in multipole space. We also find evidence that the effective dipole modulation amplitude increases with the multipole l in the range l = 2?64
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.
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.
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)
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...
Injection coupling with high amplitude transverse modes: Experimentation and simulation
Mery, Yoann; Ducruix, Sébastien; Scouflaire, Philippe; Candel, Sébastien
2009-06-01
High frequency combustion instabilities have technical importance in the design of liquid rocket engines. These phenomena involve a strong coupling between transverse acoustic modes and combustion. They are currently being investigated by combining experimentation and numerical simulations. On the experimental level, the coupling is examined in a model scale system featuring a multiple injector combustor (MIC) comprising five coaxial injectors fed with liquid oxygen and gaseous methane. This system is equipped with a novel VHAM actuator (Very High Amplitude Modulator) which comprises two nozzles and a rotating toothed wheel blocking the nozzles in an alternate fashion. This device was designed to obtain the highest possible levels of transverse oscillation in the MIC. After a brief review of the VHAM, this article reports cold flow experiments using this modulator. Velocity maps obtained under resonant conditions using the VHAM are examined at different instants during a cycle of oscillation. Experimental data are compared with numerical pressure and velocity fields obtained from an acoustic solver. The good agreement observed in the nozzle vicinity indicates that numerical simulations can be used to analyze the complex flow field generated by the VHAM. To cite this article: Y. Mery et al., C. R. Mecanique 337 (2009).
On the validity of mean-field amplitude equations for counterpropagating wavetrains
Pierce, R D
1994-01-01
Abstract: We rigorously establish the validity of the equations describing the evolution of one-dimensional long wavelength modulations of counterpropagating wavetrains for a hyperbolic model equation, namely the sine-Gordon equation. We consider both periodic amplitude functions and localized wavepackets. For the localized case, the wavetrains are completely decoupled at leading order, while in the periodic case the amplitude equations take the form of mean-field (nonlocal) Schrödinger equations rather than locally coupled partial differential equations. The origin of this weakened coupling is traced to a hidden translation symmetry in the linear problem, which is related to the existence of a characteristic frame traveling at the group velocity of each wavetrain. It is proved that solutions to the amplitude equations dominate the dynamics of the governing equations on asymptotically long time scales. While the details of the discussion are restricted to the class of model equations having a leading cubic n...
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
International Nuclear Information System (INIS)
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
Design of multi-channel pulse amplitude acquisition card based on NIM system
International Nuclear Information System (INIS)
It mainly analyzed the characteristics of multi-channel pulse amplitude acquisition analysis system based on the computer and Nuclear Instrument Module (NIM) standards respectively. The latter architecture was introduced, and its working principle was described. After the function analysis and indicators test for the peak stretch circuit, stretched waveforms were given with the AFG3252 as the pulse generator. According to the results of the measured data processing, the pulse amplitude spectrum was drawn out, and its FWHM (Full Width at Half Maximum) was about 0.075%. After running for more than 200 hours, it has been proved that the NIM data acquisition system composed by the multi-channel amplitude acquisition card and the host PC was stable and it can be met the requirements of small-scale multi-parameter data acquisition systems preliminarily. (authors)
Electronic modules for fast data processing from hodoscopic telescopes
International Nuclear Information System (INIS)
Spectral electronic modules - the majority logic module and the module of logic comparison, which are, correspondingly, 16-input digital coincidence circuit with varing selection multiplicity and the circuit of bit-to-bit comparison with two 13-bit words are described. The modules are assigned for fast logic processing of signals from hodoscopic scintilliator counters. The example of the modules employment in the setup for single particle selection in the residual electron, muon and hadron beams behind the ''Proza'' and ''Sigma'' setups is given
Origin of positive magnetoresistance in small-amplitude unidirectional lateral superlattices
Endo, Akira; Iye, Yasuhiro
2005-01-01
We report quantitative analysis of positive magnetoresistance (PMR) for unidirectional-lateral-superlattice samples with relatively small periods (a=92-184 nm) and modulation amplitudes (V_0=0.015-0.25 meV). By comparing observed PMR's with ones calculated using experimentally obtained mobilities, quantum mobilities, and V_0's, it is shown that contribution from streaming orbits (SO) accounts for only small fraction of the total PMR. For small V_0, the limiting magnetic fiel...
Zeroing in on Supersymmetric Radiation Amplitude Zeros
Hewett, JoAnne L; Rizzo, Thomas G
2011-01-01
Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p_T spectrum of the softest lepton in the trilepton $\\chi_1^\\pm \\chi_2^0$ decay channel to that of a control process such as $\\chi_1^+ \\chi_1^-$ or $\\chi_2^0 \\chi_2^0$. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.
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
A fresh look at generalized Veneziano amplitudes
Fairlie, David B
1994-01-01
The dual resonance model, which was a precursor of string theory was based upon the idea that two-particle scattering amplitudes should be expressible equivalently as a sum of contributions of an infinite number of s channel poles each corresponding to a finite number of particles with definite spin, or as a similar sum of t channel poles. The famous example of Veneziano \\cite{ven} satisfies all these requirements, and is additionally ghost free.We recall other trajectories which provide solutions to the duality constraints, e.g. the general Mobi\\"us trajectories and the logarithmic trajectories, which were thought to be lacking this last feature. We however demonstrate, partly empirically, the existence of a regime within a particular deformation of the Veneziano amplitude for logarithmic trajectories for which the amplitude remains ghost free.
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
Fréchet kernels for body wave amplitudes
Dahlen, F. A.; Baig, A. M.
2001-12-01
We derive a 3-D Fréchet sensitivity kernel relating the root-mean-square amplitude of a far-field, broad-band body-wave pulse to laterally heterogeneous seismic slowness variations within the earth. Unlike the ``banana-doughnut'' sensitivity kernel for a cross-correlation traveltime, the amplitude Fréchet kernel for a turning wave is maximally sensitive, rather than completely insensitive, to the 3-D slowness perturbation along the central source-to-receiver ray. In the asymptotic limit of an infinite-frequency pulse, our 3-D amplitude kernel formulation is consistent with the dominant 1-D integral involving the double cross-path derivative of the slowness perturbation along the unperturbed geometrical ray.
Compensating For Unbalance In Pulse-Code Phase Modulation
Nguyen, Tien M.; Hinedi, Sami M.
1995-01-01
Algorithm proposed for use in pulse-code phase-modulation transmitter in which non-return-to-zero (NRZ) or biphase data modulated directly onto radio-frequency residual carrier signal. Devised to compensate somewhat for effect, upon distant receiver, of unbalance in stream of transmitted data. Formulated to compute combinations of modulation index, data rate, and transmitter power compensating for measured unbalance in transmitted data stream.
Amplitude and phase in quantum optics
International Nuclear Information System (INIS)
A quantum description of light - what else could be meant than that light consists of photons? What could be more apparent than that a quantum description requires one to think in terms of photons? Nonetheless, in this paper, the author asks the reader to set aside the notion of photons and to think of light in nearly classical terms. A beam of light is viewed as an electromagnetic field with a nearly sinusoidal time dependence. The time dependence is characterized by a mean amplitude and a mean phase, on which are superposed fluctuations in amplitude and phase-fluctuations which when reduced to a minimum are quantum in origin
Elastic Amplitudes and Observables in pp Scattering
Ferreira, Erasmo; Kohara, Anderson Kendi
2014-01-01
Using a unified analytic representation for the elastic scattering amplitudes of pp scattering valid for all high energy region, the behavior of observables in the LHC collisions in the range $\\sqrt{s}$ = 2.76 - 14 TeV is discussed. Similarly to the case of 7 TeV data, the proposed amplitudes give excellent description of the preliminary 8 TeV data. We discuss the expected energy dependence of the observable quantities, and present predictions for the experiments at 2.76, 13 and 14 TeV.
Elastic amplitudes and observables in pp scattering
Kohara, A. Kendi; Ferreira, Erasmo; Kodama, Takeshi
2015-04-01
Using a unified analytic representation for the elastic scattering amplitudes of pp scattering valid for all high energy region, the behavior of observables in the LHC collisions in the range ?{s }=2.76 - 14 TeV is discussed. Similarly to the case of 7 TeV data, the proposed amplitudes give excellent description of the preliminary 8 TeV data. We discuss the expected energy dependence of the observable quantities, and present predictions for the experiments at 2.76, 13 and 14 TeV.
Singularity Structure of Maximally Supersymmetric Scattering Amplitudes
DEFF Research Database (Denmark)
Arkani-Hamed, Nima; Bourjaily, Jacob L.
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) supergravity theory (SUGRA).
Protecting quantum entanglement from amplitude damping
International Nuclear Information System (INIS)
Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently studied methods, the scheme presented here does not require weak measurement in the reversal process, leading to a faster recovery of entanglement. We propose a possible experimental implementation based on linear optical system. (paper)
King, Donald B. (Albuquerque, NM); Sadwick, Laurence P. (Salt Lake City, UT); Wernsman, Bernard R. (Clairton, PA)
2002-06-18
Modules of assembled microminiature thermionic converters (MTCs) having high energy-conversion efficiencies and variable operating temperatures manufactured using MEMS manufacturing techniques including chemical vapor deposition. The MTCs incorporate cathode to anode spacing of about 1 micron or less and use cathode and anode materials having work functions ranging from about 1 eV to about 3 eV. The MTCs also exhibit maximum efficiencies of just under 30%, and thousands of the devices and modules can be fabricated at modest costs.
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.
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
Extended Method of Digital Modulation Recognition and Its Testing
Directory of Open Access Journals (Sweden)
A. Kubankova
2011-04-01
Full Text Available The paper describes a new method for the classification of digital modulations. ASK, 2FSK, 4FSK, MSK, BPSK, QPSK, 8PSK and 16QAM were chosen for recognition as best known digital modulations used in modern communication technologies. The maximum value of the spectral power density of the normalized-centered instantaneous amplitude of the received signal is used to discriminate between frequency modulations (2FSK, 4FSK and MSK on one hand and amplitude and phase modulations (ASK, BPSK, QPSK, 8PSK and 16QAM on the other hand. Then the 2FSK, 4FSK and MSK modulations are classified by means of spectrums. The histograms of the instantaneous phase are used to discriminate between ASK, BPSK, QPSK, 8PSK and 16QAM. The method designed was tested with simulated and measured signals corrupted by white Gaussian noise.
Crack propagation under variable amplitude loading
Scientific Electronic Library Online (English)
Miloudi, Abdelkader; Zemri, Mokhtar; Benguediab, Mohamed; Mazari, Mohamed; Amrouche, Abdelwaheb.
1161-11-01
Full Text Available 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.
Directory of Open Access Journals (Sweden)
Xiangbin Yu
2012-05-01
Full Text Available Differential space-time coding (DSTC technique has become a good choice when channel estimations are difficult to obtain in multiple antennas system. On the basis of analyzing the existing DSTC schemes, by introducing multi-level quadrature amplitude modulation (MQAM and matrix transform method, we develop a multi-amplitude differential space-time block coding (STBC scheme for square or non-square code matrix in MIMO systems, and give the derivation of calculation formulae of the coding advantage in detail. The developed scheme can effectively avoid the performance loss of conventional DSTC schemes based on PSK modulation (i.e. single amplitude DSTC in high spectrum efficiency. It can be applied to non-square code matrix case, and thus overcomes the shortcoming that existing DSTC schemes are only suitable for square code matrix. Compared with single amplitude DSTC schemes, our scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes. Moreover, our scheme has linear decoding complexity, higher coding advantage, and higher code rate for more than two antennas. The simulations results show that the proposed scheme can provide lower BER than the existing single amplitude differential STBC schemes for both square and non-square code matrices.
Evaluation of transient amplitudes between Dirac spinors
International Nuclear Information System (INIS)
The authors present a simple method for expressing transition amplitudes between fermion states of definite polarization in terms of momenta and polarization vectors only, rather than ?-matrices and spinors. As an illustration, Coulomb and Bhabha scattering for polarized particles is evaluated. (Auth.)
Amplitude Correction Factors of KVN Observations
Lee, Sang-Sung; Oh, Chung Sik; Kim, Hyo Ryoung; Kim, Jongsoo; Jung, Taehyun; Oh, Se-Jin; Roh, Duk-Gyoo; Jung, Dong-Kyu; Yeom, Jae-Hwan
2015-01-01
We report results of investigation of amplitude calibration for very long baseline interferometry (VLBI) observations with Korean VLBI Network (KVN). Amplitude correction factors are estimated based on comparison of KVN observations at 22~GHz correlated by Daejeon hardware correlator and DiFX software correlator in Korea Astronomy and Space Science Institute (KASI) with Very Long Baseline Array (VLBA) observations at 22~GHz by DiFX software correlator in National Radio Astronomy Observatory (NRAO). We used the observations for compact radio sources, 3C~454.3 and NRAO~512, which are almost unresolved for baselines in a range of 350-477~km. Visibility data of the sources obtained with similar baselines at KVN and VLBA are selected, fringe-fitted, calibrated, and compared for their amplitudes. We found that visibility amplitudes of KVN observations should be corrected by factors of 1.10 and 1.35 when correlated by DiFX and Daejeon correlators, respectively. These correction factors are attributed to the combinat...
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.
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.
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.
Polarimetric Imaging using Two Photoelastic Modulators
Wang, Yu; Cunningham, Thomas; Diner, David; Davis, Edgar; Sun, Chao; Hancock, Bruce; Gutt, Gary; Zan, Jason; Raouf, Nasrat
2009-01-01
A method of polarimetric imaging, now undergoing development, involves the use of two photoelastic modulators in series, driven at equal amplitude but at different frequencies. The net effect on a beam of light is to cause (1) the direction of its polarization to rotate at the average of two excitation frequencies and (2) the amplitude of its polarization to be modulated at the beat frequency (the difference between the two excitation frequencies). The resulting modulated optical light beam is made to pass through a polarizing filter and is detected at the beat frequency, which can be chosen to equal the frame rate of an electronic camera or the rate of sampling the outputs of photodetectors in an array. The method was conceived to satisfy a need to perform highly accurate polarimetric imaging, without cross-talk between polarization channels, at frame rates of the order of tens of hertz. The use of electro-optical modulators is necessitated by a need to obtain accuracy greater than that attainable by use of static polarizing filters over separate fixed detectors. For imaging, photoelastic modulators are preferable to such other electrio-optical modulators as Kerr cells and Pockels cells in that photoelastic modulators operate at lower voltages, have greater angular acceptances, and are easier to use. Prior to the conception of the present method, polarimetric imaging at frame rates of tens of hertz using photoelastic modulators was not possible because the resonance frequencies of photoelastic modulators usually lie in the range from about 20 to about 100 kHz.
Photon energy analysis by reflectivity modulation
International Nuclear Information System (INIS)
X-ray mirror reflectivity versus energy is approximately a step function. By dithering the orientation of an X-ray mirror and phase detecting the reflected photons, one obtains a response function which is the derivative of this step function. A photon response function with a narrow energy resolution is thus produced. This photon energy analysis by reflectivity modulation is analogous to a modulated retarding grid electron energy analyzer. The energy resolution and the peak efficiency of the response function are determined by the optical constants or the mirror, the amplitude of the dither and the collimation of the photons, so the signal can be increased at the expense of energy resolution by altering the dither amplitude. Although the resolving power is low compared with what can be achieved with crystals, reflectivity modulation has several advantages over crystal based monochromators and spectrometers. Reflectivity modulation can be used over a very large energy range, including soft X-rays. For focused applications, the surface of an X-ray mirror is more easily figured than the diffracting planes of a crystal. The response function of a mirror is harmonic free and most importantly, the signal amplitude can be much higher than from crystals. (orig.)
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.
Nan, Yi-Bing; Tang, Yi; Zhang, Li-Jun; Zheng, Cheng; Wang, Jing
2015-05-01
Satellite vibrations during exposure will lead to pixel aliasing of remote sensors, resulting in the deterioration of image quality. In this paper, we expose the problem and discuss the characteristics of satellite vibrations, and then present a pixel mixing model. The idea of mean mixing ratio (MMR) is proposed. MMR computations for different frequencies are implemented. In the mixing model, a coefficient matrix is introduced to estimate each mixed pixel. Thus, the simulation of degraded image can be performed when the vibration attitudes are known. The computation of MMR takes into consideration the influences of various frequencies and amplitudes. Therefore, the roles of these parameters played in the degradation progress are identified. Computations show that under the same vibration amplitude, the influence of vibrations fluctuates with the variation of frequency. The fluctuation becomes smaller as the frequency rises. Two kinds of vibration imaging experiments are performed: different amplitudes with the same frequency and different frequencies with the same amplitude. Results are found to be in very good agreement with the theoretical results. MMR has a better description of image quality than modulation transfer function (MTF). The influence of vibrations is determined mainly by the amplitude rather than the frequency. The influence of vibrations on image quality becomes gradually stable with the increase of frequency. Project supported by the National Basic Research Program of China (Grant No. 2013CB329202) and the Basic Industrial Technology Project of China (Grant No. J312012B002).
Arora, Sumitra; Mukherjee, Irani; Kumar, Aman; Garg, D K
2014-01-01
The integrated pest management (IPM) modules of pesticide schedule on Basmati rice were validated at field experiments conducted in Northern India for consecutive 3 years (2005-2008). The pesticide residues were found below the detectable limit (basmati rice as safe and economical with pesticide residue-free rice grains. PMID:23996682
Amplitude Saturation in Beta Cephei Models - Preliminary Results
Smolec, R; Smolec, Radoslaw; Moskalik, Pawel
2006-01-01
Using nonlinear hydrocodes we have calculated single mode saturation amplitudes for beta Cephei models. Predicted saturation amplitudes are systematically higher than amplitudes observed in beta Cephei variables, even in monoperiodic ones. We argue that collective saturation of the pulsation instability by a dozen or so acoustic modes brings the theoretical amplitudes to the observed level.
Dukkipati, Ambedkar; Pai, Nithish; Francis, Maria; Dubey, Abhishek
2014-01-01
In this paper we generalize the Macaulay-Buchberger basis theorem to the case, where the residue class polynomial ring over a Noetherian ring is not necessarily a free module. Recently, this theorem has been extended from polynomial rings over fields to rings, when residue class polynomial ring is free in (Francis & Dukkipati, 2014). As an application of this generalization we develop a theory of border bases for ideals where the corresponding residue class rings are finitel...
Deng, Yuanmu; Pandian, Ramasamy P.; Ahmad, Rizwan; Kuppusamy, Periannan; Zweier, Jay L.
2006-01-01
Magnetic field modulation in CW electron paramagnetic resonance (EPR) is used for signal detection. However, it can also distort signal lineshape. In experiments where the linewidth information is of particular importance, small modulation amplitude is usually used to limit the lineshape distortion. The use of small modulation amplitude, however, results in low signal-to-noise ratio and therefore affects the precision of linewidth measurements. Recently, a new spectral simulation model has be...
Statistics of Langmuir wave amplitudes observed inside Saturn's foreshock by the Cassini spacecraft
Píša, David; Hospodarsky, George B.; Kurth, William S.; Santolík, Ond?ej; Sou?ek, Jan; Gurnett, Donald A.; Masters, Adam; Hill, Matthew E.
2015-04-01
We present the first systematic study of Langmuir wave amplitudes in Saturn's foreshock using the Cassini Radio and Plasma Wave Science/Wideband Receiver measurements. We analyzed all foreshock crossings from June 2004 to December 2009 using an automatic method to identify Langmuir waves. Using this method, almost 3 × 105 waveform intervals of typical duration of about a minute were selected. For each selected waveform interval the position of the satellite inside the foreshock was calculated using an adaptive bow shock model, which was parametrized by the observed magnetic field and plasma data. We determined the wave amplitudes for all waveform intervals, and we found that the probability density function amplitudes follow a lognormal distribution with a power law tail. A nonlinear fit for this tail gives a power law exponent of -1.37 ± 0.01. The distribution of amplitudes as a function of the depth in the foreshock shows the onset of the waves near the upstream boundary with its maximum slightly shifted inside the foreshock (˜1 RS). The amplitudes then fall off with increasing depth in the downstream region. Our results are in agreement with previous observations and roughly follow the generally accepted stochastic growth theory mechanism for the foreshock region, with an exception at the highest observed amplitudes. The estimated energy density ratio W for largest amplitudes does not exceed 10-2, suggesting that modulational instability is not relevant for a large majority of waves. The decay instability can be important for the stronger electrostatic waves in Saturn's foreshock, as was previously reported for multiple solar system planets.
Feng, Zhipeng; Zuo, Ming J.; Qu, Jian; Tian, Tao; Liu, Zhiliang
2013-10-01
The vibration signals of faulty planetary gearboxes have complicated spectral structures due to the amplitude modulation and frequency modulation (AMFM) nature of gear damage induced vibration and the additional multiplicative amplitude modulation (AM) effect caused by the time-varying vibration transfer paths (for local gear damage case) and the passing planets (for distributed gear damage case). The spectral complexity leads to the difficulty in fault diagnosis of planetary gearboxes. Observing that both the amplitude envelope and the instantaneous frequency of planetary gearbox vibration signals are associated with the characteristic frequency of the faulty gear, a joint amplitude and frequency demodulation method is proposed for fault diagnosis of planetary gearboxes. In order to satisfy the mono-component requirement by instantaneous frequency estimation, a signal is firstly decomposed into product functions (PF) using the local mean decomposition (LMD) method. Then, the earliest extracted PF that has an instantaneous frequency fluctuating around the gear meshing frequency or its harmonics is chosen for further analysis, because it contains most of the information about the gear fault. The amplitude demodulation analysis can be accomplished through Fourier transforming the amplitude envelope of the chosen PF. For the frequency demodulation analysis, Fourier transform is applied to the estimated instantaneous frequency of the chosen PF to reveal its fluctuating frequency, thus obtaining the spectrum of the instantaneous frequency. By joint application of the amplitude and frequency demodulation methods, planetary gearbox faults can be diagnosed by matching the dominant peaks in the envelope spectrum and the spectrum of instantaneous frequency with the theoretical characteristic frequencies of faulty gears. The performance of the proposed method is illustrated by simulated signal analysis, and is validated by experimental signal analysis of a lab planetary gearbox with intentionally created pitting and naturally developed wear.
Algebraic evaluation of rational polynomials in one-loop amplitudes
Binoth, T; Marlen-Heinrich, G
2007-01-01
One-loop amplitudes are to a large extent determined by their unitarity cuts in four dimensions. We show that the remaining rational terms can be obtained from the ultraviolet behaviour of the amplitude, and determine universal form factors for these rational parts by applying reduction techniques to the Feynman diagrammatic representation of the amplitude. The method is valid for massless and massive internal particles. We illustrate this method by evaluating the rational terms of the one-loop amplitudes for gg --> H, the 4-photon amplitude, the amplitude for 2 photons plus 3 gluons and the 6-photon amplitude.
40 CFR 721.4500 - Isopropylamine distillation residues and ethylamine distillation residues.
2010-07-01
... 2010-07-01 false Isopropylamine distillation residues and ethylamine distillation residues. 721.4500 Section 721...Substances § 721.4500 Isopropylamine distillation residues and ethylamine distillation...
Fungicide residues in strawberry processing.
Will, F; Krüger, E
1999-03-01
The fate of three fungicides (dichlofluanid, procymidone, and iprodione) applied under field conditions was studied during strawberry processing to juice, wine, and jam. An untreated control was compared to raw material treated with fungicides according to recommended doses and to a sample with 6-fold higher application rates. The highest residue values were found in the pomace after pressing. Residue values in readily produced juices and fruit wines were very low and did not exceed legally required maximum residue levels. Generally, processing steps such as pressing and clarification diminished fungicide residues from 50 to 100%. If the whole fruit is processed, as in fruit preparations or jam, the residue levels remain higher due to missing processing steps. PMID:10552381
Statistical inference on residual life
Jeong, Jong-Hyeon
2014-01-01
This is a monograph on the concept of residual life, which is an alternative summary measure of time-to-event data, or survival data. The mean residual life has been used for many years under the name of life expectancy, so it is a natural concept for summarizing survival or reliability data. It is also more interpretable than the popular hazard function, especially for communications between patients and physicians regarding the efficacy of a new drug in the medical field. This book reviews existing statistical methods to infer the residual life distribution. The review and comparison includes existing inference methods for mean and median, or quantile, residual life analysis through medical data examples. The concept of the residual life is also extended to competing risks analysis. The targeted audience includes biostatisticians, graduate students, and PhD (bio)statisticians. Knowledge in survival analysis at an introductory graduate level is advisable prior to reading this book.
Reduction of EMI by Combining Interleaving and Modulation Techniques in Multiconverter Topology
Mon González, Juan; Gago Barrio, Javier; González Díez, David; Balcells Sendra, Josep; Fernández García, Raúl; Gil Galí, Ignacio
2009-01-01
In this paper an evaluation of different modulations techniques that combine switching frequency modulation and interleaving is presented. The objective of these modulations is to cancel certain harmonics of EMI and to reduce the amplitude of the remaining harmonics. A four channel parallel buck converter has been used in order to evaluate the modulations proposed. According experimental results, significant reduction of EMI is possible by combining both techniques instead of using them...
Automatic prediction of catalytic residues by modeling residue structural neighborhood
Directory of Open Access Journals (Sweden)
Passerini Andrea
2010-03-01
Full Text Available Abstract Background Prediction of catalytic residues is a major step in characterizing the function of enzymes. In its simpler formulation, the problem can be cast into a binary classification task at the residue level, by predicting whether the residue is directly involved in the catalytic process. The task is quite hard also when structural information is available, due to the rather wide range of roles a functional residue can play and to the large imbalance between the number of catalytic and non-catalytic residues. Results We developed an effective representation of structural information by modeling spherical regions around candidate residues, and extracting statistics on the properties of their content such as physico-chemical properties, atomic density, flexibility, presence of water molecules. We trained an SVM classifier combining our features with sequence-based information and previously developed 3D features, and compared its performance with the most recent state-of-the-art approaches on different benchmark datasets. We further analyzed the discriminant power of the information provided by the presence of heterogens in the residue neighborhood. Conclusions Our structure-based method achieves consistent improvements on all tested datasets over both sequence-based and structure-based state-of-the-art approaches. Structural neighborhood information is shown to be responsible for such results, and predicting the presence of nearby heterogens seems to be a promising direction for further improvements.
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.
Nonlinear dynamics of lasers with intracavity modulation of ellipticity
Kul'minskii, A. M.; Loiko, Yu V.; Voitovich, A. P.
2004-02-01
In this work we consider polarization dynamics of a class A vector laser subject to new kind of vector modulation which drives the eigenmode ellipticity. Such a modulation can be accomplished by an intracavity device consisting of two crossed quarterwave plates with Faraday element between them. It is found that sinusoidal modulation of the eigenmode ellipticity is directly transferred to the polarization parameters of the emitted field only at small amplitude of modulation. Among interesting features in the laser dynamic behaviour we report on resonant and quasiperiodic behaviours in the vicinity of the polarization relaxation frequency.
Nonlinear dynamics of lasers with intracavity modulation of ellipticity
International Nuclear Information System (INIS)
In this work we consider polarization dynamics of a class A vector laser subject to new kind of vector modulation which drives the eigenmode ellipticity. Such a modulation can be accomplished by an intracavity device consisting of two crossed quarterwave plates with Faraday element between them. It is found that sinusoidal modulation of the eigenmode ellipticity is directly transferred to the polarization parameters of the emitted field only at small amplitude of modulation. Among interesting features in the laser dynamic behaviour we report on resonant and quasiperiodic behaviours in the vicinity of the polarization relaxation frequency
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.
Droit, C.; Martin, G.; Ballandras, S.; Friedt, J.-M.
2010-05-01
We demonstrate the wireless conversion of frequency modulation to amplitude modulation by radio frequency resonators as means of accurately determining the resonance frequency of passive acoustoelectronic sensors. The emitted frequency modulated radio frequency pulses are generated by a pulsed radar for probing a surface acoustic wave based sensor. The sharp sign transition of the amplitude modulated received signal provides a signal on which a feedback loop is locked to monitor the resonance signal. The strategy is demonstrated using a full software implementation on a generic hardware, resulting in 2 Hz resolution at 1 s integration time limited by the proportional feedback loop.
Large amplitude waves and fields in plasmas
International Nuclear Information System (INIS)
In this review, based mostly on the results of the recent workshop on ''Large Amplitude Waves and Fields in Plasmas'' held at ICTP (Trieste, Italy) in May 1989 during the Spring College on Plasma Physics, I will mostly concentrate on underdense, cold, homogeneous plasmas, discussing some of the alternative (to fusion) uses of laser-plasma interaction. In Part I an outline of some basic non-linear processes is given, together with some recent experimental results. The processes are chosen because of their relevance to the applications or because new interesting developments have been reported at the ICTP workshop (or both). In Part II the excitation mechanisms and uses of large amplitude plasma waves are presented: these include phase-conjugation in plasmas, plasma based accelerators (beat-wave, plasma wake-field and laser wake-field), plasma lenses and plasma wigglers for Free Electron Lasers. (author)
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.)
Differential Equations, Associators, and Recurrences for Amplitudes
Puhlfuerst, Georg
2015-01-01
We provide new methods to straightforwardly obtain compact and analytic expressions for epsilon-expansions of functions appearing in both field and string theory amplitudes. An algebraic method is presented to explicitly solve for recurrence relations connecting different epsilon-orders of a power series solution in epsilon of a differential equation. This strategy generalizes the usual iteration by Picard's method. Our tools are demonstrated for generalized hypergeometric functions. Furthermore, we match the epsilon-expansion of specific generalized hypergeometric functions with the underlying Drinfeld associator with proper Lie algebra and monodromy representations. We also setup up our tools for computing epsilon-expansions for solutions to generic first-order Fuchsian equations (Schlesinger system). Finally, we apply our methods to systematically get compact and explicit alpha'-expansions of tree-level superstring amplitudes to any order in alpha'.
Limit on the pion distribution amplitude
International Nuclear Information System (INIS)
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????(Q2). The resulting upper limit on the pion transition form factor is compared with existing data published by CLEO, BaBar and Belle Collaborations. (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.
Optical twists in phase and amplitude.
Daria, Vincent R; Palima, Darwin Z; Glückstad, Jesper
2011-01-17
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. PMID:21263587
ABJM amplitudes and WL at finite N
Bianchi, Marco S; Leoni, Matias; Mauri, Andrea; Penati, Silvia; Santambrogio, Alberto
2013-01-01
We evaluate ABJM observables at two loops, for any value of the rank N of the gauge group. We compute the color subleading contributions to the four-point scattering amplitude in ABJM at two loops. Contrary to the four dimensional case, IR divergent N-subleading contributions are proportional to leading poles in the regularization parameter. We then exploit the non-planar calculation for the amplitude to derive an expression for the two-loop Sudakov form factor at any N. In the planar limit the result coincides with the one recently obtained in literature by using Feynman diagrams and unitarity. Finally, we analyze the subleading contributions to the light-like four-cusps Wilson loop and interpret the result in terms of the non-abelian exponentiation theorem. All these perturbative results satisfy the uniform transcendentality principle, hinting at its validity in ABJM beyond the planar limit.
Quantum Amplitudes in Black-Hole Evaporation II. Spin-0 Amplitude
Farley, A. N. St J.; D Eath, P. D.
2005-01-01
This work on spin-0 amplitudes in black-hole evaporation is based on the underlying results and methods outlined in our first paper, "I. Complex Approach". The main result here, and the model calculation for work on all higher spins, as described in several further papers, is the computation of the quantum amplitude (rather than merely the probability) for a given slightly anisotropic configuration of a scalar field $\\phi$ on a space-like hypersurface $\\Sigma_F$ at a very la...
Amplitudes in Noncritical Dimensions and Dimensional Regularization
Murakami, Koichi; Ishibashi, Nobuyuki
2011-01-01
We study how the dimensional regularization works in the light-cone gauge string field theory. We show that it is not necessary to add a contact term to the string field theory action as a counter term in this regularization at least at the tree level. We also investigate the one-loop amplitudes of the bosonic theory in noncritical dimensions and show that they are modular invariant.
Finite amplitude standing waves in metallic rods
Campos-Pozuelo, Cleofé; Gallego Juárez, Juan Antonio
1995-01-01
Large-amplitude extensional standing waves in metals are studied theoretically and experimentally. Starting from the nonlinear elastodynamic equation for perfectly elastic solids, a one-dimensional second-order model is formulated for resonant rods. Losses are neglected and superposition of forward and backward waves is assumed. Spatial distributions of the force and particle velocity are obtained theoretically as well as the waveforms. The experimental work consists of measuring ...
CMB Fluctuation Amplitude from Dark Energy Partitions
Lindesay, James V.; Noyes, H. Pierre; Jones, E. D.
2004-01-01
It is assumed that the dark energy observed today is frozen as a result of a phase transition involving the source of that energy. Postulating that the dark energy de-coherence which results from this phase transition drives statistical variations in the energy density specifies a class of cosmological models in which the cosmic microwave background (CMB) fluctuation amplitude at last scattering is approximately $10^{-5}$.
On the infinities of closed superstring amplitudes
International Nuclear Information System (INIS)
We present an analysis of possible infinities that may be present in uncompactified multi-loop heterotic and type II superstring amplitudes constructed, without use of the short-string limit, in the light-cone gauge, and with use of a closed SUSY field theory algebra. Various types of degenerations of the integrand are discussed on the string world-sheet. No infinities are found, modulo (for type II) a particular identity for Green's functions. (author). 13 refs
Semiclassical scattering amplitudes of dressed gravitons
Kang, Kyungsik; Kondrashuk, Igor
2004-01-01
We consider effective action for the Einstein gravity and show that dressed mean fields are actual variables of the effective action. Kernels of this effective action expressed in terms of dressed effective fields are constituent parts of scattering amplitudes for gravitons. Possible applications to the graviton scattering and black hole formation are discussed at the semiclassical level. In particular, we consider graviton scattering in four dimensions based on the Lipatov ...
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.
Automatic Generation of Tree Level Helicity Amplitudes
Stelzer, T.; Long, W. F.
1994-01-01
The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.
OTDM-to-WDM Conversion of Complex Modulation Formats by Time-Domain Optical Fourier Transformation
DEFF Research Database (Denmark)
Palushani, Evarist; Richter, T.
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.
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...
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.
Coding stimulus amplitude by correlated neural activity
Metzen, Michael G.; Ávila-Åkerberg, Oscar; Chacron, Maurice J.
2015-01-01
While correlated activity is observed ubiquitously in the brain, its role in neural coding has remained controversial. Recent experimental results have demonstrated that correlated but not single-neuron activity can encode the detailed time course of the instantaneous amplitude (i.e., envelope) of a stimulus. These have furthermore demonstrated that such coding required and was optimal for a nonzero level of neural variability. However, a theoretical understanding of these results is still lacking. Here we provide a comprehensive theoretical framework explaining these experimental findings. Specifically, we use linear response theory to derive an expression relating the correlation coefficient to the instantaneous stimulus amplitude, which takes into account key single-neuron properties such as firing rate and variability as quantified by the coefficient of variation. The theoretical prediction was in excellent agreement with numerical simulations of various integrate-and-fire type neuron models for various parameter values. Further, we demonstrate a form of stochastic resonance as optimal coding of stimulus variance by correlated activity occurs for a nonzero value of noise intensity. Thus, our results provide a theoretical explanation of the phenomenon by which correlated but not single-neuron activity can code for stimulus amplitude and how key single-neuron properties such as firing rate and variability influence such coding. Correlation coding by correlated but not single-neuron activity is thus predicted to be a ubiquitous feature of sensory processing for neurons responding to weak input. PMID:25974537
Zeroing in on Supersymmetric Radiation Amplitude Zeros
Energy Technology Data Exchange (ETDEWEB)
Hewett, JoAnne L.; Ismail, Ahmed; Rizzo, Thomas G.; /SLAC
2012-02-15
Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p{sub T} spectrum of the softest lepton in the trilepton {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} decay channel to that of a control process such as {tilde {chi}}{sub 1}{sup +} {tilde {chi}}{sub 1}{sup -} or {tilde {chi}}{sub 2}{sup 0} {tilde {chi}}{sub 2}{sup 0}. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.
Coding stimulus amplitude by correlated neural activity
Metzen, Michael G.; Ávila-Åkerberg, Oscar; Chacron, Maurice J.
2015-04-01
While correlated activity is observed ubiquitously in the brain, its role in neural coding has remained controversial. Recent experimental results have demonstrated that correlated but not single-neuron activity can encode the detailed time course of the instantaneous amplitude (i.e., envelope) of a stimulus. These have furthermore demonstrated that such coding required and was optimal for a nonzero level of neural variability. However, a theoretical understanding of these results is still lacking. Here we provide a comprehensive theoretical framework explaining these experimental findings. Specifically, we use linear response theory to derive an expression relating the correlation coefficient to the instantaneous stimulus amplitude, which takes into account key single-neuron properties such as firing rate and variability as quantified by the coefficient of variation. The theoretical prediction was in excellent agreement with numerical simulations of various integrate-and-fire type neuron models for various parameter values. Further, we demonstrate a form of stochastic resonance as optimal coding of stimulus variance by correlated activity occurs for a nonzero value of noise intensity. Thus, our results provide a theoretical explanation of the phenomenon by which correlated but not single-neuron activity can code for stimulus amplitude and how key single-neuron properties such as firing rate and variability influence such coding. Correlation coding by correlated but not single-neuron activity is thus predicted to be a ubiquitous feature of sensory processing for neurons responding to weak input.
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
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...
Kashiwase, Yoshiyuki; Matsumiya, Kazumichi; Kuriki, Ichiro; Shioiri, Satoshi
2012-08-01
Endogenous attention modulates the amplitude and phase coherence of steady-state visual-evoked potentials (SSVEPs). In efforts to decipher the neural mechanisms of attentional modulation, we compared the time course of attentional modulation of SSVEP amplitude (thought to reflect the magnitude of neural population activity) and phase coherence (thought to reflect neural response synchronization). We presented two stimuli flickering at different frequencies in the left and right visual hemifields and asked observers to shift their attention to either stimulus. Our results demonstrated that attention increased SSVEP phase coherence earlier than it increased SSVEP amplitude, with a positive correlation between the attentional modulations of SSVEP phase coherence and amplitude. Furthermore, the behavioral dynamics of attention shifts were more closely associated with changes in phase coherence than with changes in amplitude. These results are consistent with the possibility that attention increases neural response synchronization, which in turn leads to increased neural population activity. PMID:22360591
Module for three-pulsed power system
International Nuclear Information System (INIS)
A module is designed for six-channel, three-pulsed power system, which is based on MHz repeating rate burst high-voltage generator with Blumlein pulse forming lines connected in parallel and multi-stage laser trigger system. Parameter designs of Blumlein device, confluent/blocking network, and trigger system are discussed. The analysis and simulation results show that the module meets the needs of multi-pulse linear induction accelerator. The output voltage with an amplitude of 300 kV, time jitter less than 2.3 ns (standard deviation), and repetition rate of MHz level is achieved. (authors)
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.
Pion-to-photon transition distribution amplitudes in the non-local chiral quark model
Kotko, Piotr; Praszalowicz, Michal
2008-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDA's. We note only residual dependence on the precise form of the cut-off function, however vector TDA th...
Signal processing module for the liquid xenon calorimeter of CMD-3 detector
International Nuclear Information System (INIS)
The coordinate system of a liquid xenon (LXe) calorimeter includes 2112 cathode strips. The charges collected by the strips are to be measured. A special Signal Processing Module has been developed which performs all actions necessary for charge measurement-amplification and shaping of analog signal, digitization, and resulting data transfer to the data acquisition system. In this paper the selected amplitude measurement technique, the estimation of achievable accuracy of amplitude measurement, and the results of module testing are described.
Glass Difractive Optical Elements (DOEs) with complex modulation DLC thin film coated
Marina Sparvoli; Ronaldo Domingues Mansano
2008-01-01
We developed a complex (amplitude and phase) modulation Diffractive Optical Element (DOE) with four phase levels, which is based in a glass substrate coated with DLC (Diamond Like Carbon) thin film as the amplitude modulator. The DLC film was deposited by magnetron reactive sputtering with a graphite target and methane gas in an optical glass surface. The glass and DLC film roughness were measured using non destructive methods, such as a high step meter, Atomic Force Microscopy and Diffuse Re...
Module Biprojective and Module Biflat Banach Algebras
Bodaghi, Abasalt; Amini, Massoud
2009-01-01
In this paper we define module biprojctivity and module biflatness for a Banach algebra which is a Banach module over another Banach algebra with compatible actions, and find their relation to classical biprojectivity and biflatness. As a typical example, We show that for an inverse semigroup $S$ with an upward directed set of idempotents $E$, the semigroup algebra $ \\ell ^{1}(S)$, as an $\\ell ^{1}(E)$-module, is module biprojective if and only if an appropriate group homomo...
Jordan, T. E.; Baker, G. S.
2003-12-01
Amplitude and phase variation with offset analysis of ground penetrating radar data (APVO/GPR) can improve the differentiation of non-aqueous phase liquid (NAPL) from stratigraphic changes. Previous controlled experiments have shown that common offset (CO) GPR methods can detect the presence of NAPL in soil by examining amplitude and travel time (velocity) anomalies. Unfortunately, stratigraphic changes such as the presence of a silt or clay lens or perched water table may produce similar amplitude and velocity anomalies. Therefore, it is difficult to delineate NAPL in a terrain with unknown stratigraphy exclusively using CO data collection methods. Forward models based on the Fresnel equations predict that amplitude responses exist at various incidence angles that will allow for differentiating NAPL from hydrogeologic changes. Models generated as part of this study indicate that analyzing the difference in amplitude responses from linearly polarized electric field vertically oriented (EV) to the horizontally oriented (EH) signals at various incidence angles improves target discrimination. A case history is presented demonstrating that collecting common-midpoint (CMP) GPR data using EH and EV polarized signals at anomalous CO amplitude responses and analyzing the data using APVO and normalized residual polarization (NRP) methods can improve the detection and differentiation of NAPL from stratigraphic changes in the subsurface. These results are corroborated using a capacitively coupled resisitivity instrument and subsequent intrusive sampling.
Propoxur residues in cocoa beans
International Nuclear Information System (INIS)
Pod-bearing Amazon and Amelonado cocoa plants were sprayed with Unden 20% (propoxur, arprocarb, baygon) at the recommended rate of 210 g a.i./ha and twice the recommended rate at monthly intervals from July to October, 1976, and cured beans from the ripe pods analysed for propoxur residues by gas chromatography. In a radiotracer study with 14C-labelled propoxur, the effect of processing methods on residues and systemic uptake of propoxur from insecticide deposits on pod surfaces were also investigated. Residues did not exceed 0.03 ppm. There was no relationship between residues and harvesting time, cocoa type or rate of application. Contamination of beans with insecticide deposits on the pod surface during processing, and systemic uptake of insecticide from pod surfaces were negligible. (author)
Nitrogen availability of biogas residues
Energy Technology Data Exchange (ETDEWEB)
El-Sayed Fouda, Sara
2011-09-07
The objectives of this study were to characterize biogas residues either unseparated or separated into a liquid and a solid phase from the fermentation of different substrates with respect to their N and C content. In addition, short and long term effects of the application of these biogas residues on the N availability and N utilization by ryegrass was investigated. It is concluded that unseparated or liquid separated biogas residues provide N at least corresponding to their ammonium content and that after the first fertilizer application the C{sub org}:N{sub org} ratio of the biogas residues was a crucial factor for the N availability. After long term application, the organic N accumulated in the soil leads to an increased release of N.
Regression on Quantile Residual Life
JUNG, SIN-HO; Jeong, Jong-Hyeon; Bandos, Hanna
2009-01-01
A time-specific log-linear regression method on quantile residual lifetime is proposed. Under the proposed regression model, any quantile of a time-to-event distribution among survivors beyond a certain time point is associated with selected covariates under right censoring. Consistency and asymptotic normality of the regression estimator are established. An asymptotic test statistic is proposed to evaluate the covariate effects on the quantile residual lifetimes at a specific time point. Eva...
Parshin Residues via Coboundary Operators
Mazin, Mikhail
2007-01-01
The article consist of two main parts: an analog of the Leray Theory for Singular Varieties and its application to the Theory of Parshin's Residues. The first part is independent from the second. It uses the theory of Whitney stratifications. The second part is an application of the first. In particular, a geometric and very transparent proof of the Parshin's Reciprocity Law for residues is given.