WorldWideScience
 
 
1

Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line.  

Science.gov (United States)

A new fiber-optic technique to eliminate residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy is presented. The modulated laser output is split to pass in parallel through the gas measurement cell and an optical fiber delay line, with the modulation frequency / delay chosen to introduce a relative phase shift of pi between them. The two signals are balanced using a variable attenuator and recombined through a fiber coupler. In the absence of gas, the direct laser intensity modulation cancels, thereby eliminating the high background. The presence of gas induces a concentration-dependent imbalance at the coupler's output from which the absolute absorption profile is directly recovered with high accuracy using 1f detection. PMID:19506608

Chakraborty, Arup Lal; Ruxton, Keith; Johnstone, Walter; Lengden, Michael; Duffin, Kevin

2009-06-01

2

Amplitude Modulation Effects in Cardiac Signals  

CERN Document Server

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

Peters, Randall; Russell, Michael

2010-01-01

3

CARRIER-FREQUENCY HARMONIZATION STRUCTURE FOR ENHANCED AMPLITUDE MODULATION FUNCTION  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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-refer...

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

2013-01-01

4

Spatial amplitude and phase modulation using commercial twisted nematic LCDs  

CERN Document Server

We present a method for full spatial phase and amplitude control of a laser beam using a twisted nematic liquid crystal display combined with a spatial filter. By spatial filtering we combine four neighboring pixels into one superpixel. At each superpixel we are able to independently modulate the phase and the amplitude of light. We demonstrate experimentally the independent phase and amplitude modulation using this novel technique. Our technique does not impose special requirements on the spatial light modulator and allows precise control of fields even with imperfect modulators.

van Putten, E G; Mosk, A P

2007-01-01

5

Log-Likelihood Classification Of Quadrature Amplitude Modulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

Savita Kamboj; Sonika Soni

2013-01-01

6

Log-Likelihood Classification Of Quadrature Amplitude Modulation  

Directory of Open Access Journals (Sweden)

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.

Savita Kamboj

2013-10-01

7

Tailoring quantum superpositions with linearly polarized amplitude-modulated light  

CERN Document Server

Amplitude-modulated nonlinear magneto-optical rotation is a powerful technique that offers a possibility of controllable generation of given quantum states. In this paper, we demonstrate creation and detection of specific ground-state magnetic-sublevel superpositions in $^{87}$Rb. By appropriate tuning of the modulation frequency and magnetic-field induction the efficiency of a given coherence generation is controlled. The processes are analyzed versus different experimental parameters.S

Pustelny, S; Cincio, L; Gawlik, W

2010-01-01

8

Superposed pulse amplitude modulation for visible light communication.  

Science.gov (United States)

We propose and experimentally demonstrate a novel modulation scheme called superposed pulse amplitude modulation (SPAM) which is low-cost, insensitive to non-linearity of light emitting diode (LED). Multiple optical pulses transmit parallelly from different spatial position in the LED array and overlap linearly in free space to realize SPAM. With LED arrangement, the experimental results show that using the modulation we proposed the data rate of 120 Mbit/s with BER 1 × 10(-3) can be achieved with an optical blue filter and RC post-equalization. PMID:24514674

Li, J F; Huang, Z T; Zhang, R Q; Zeng, F X; Jiang, M; Ji, Y F

2013-12-16

9

AMPLITUDE AND PHASE MODULATION FOR ULTRASONIC WIRELESS COMMUNICATION  

Directory of Open Access Journals (Sweden)

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.

Nan Gao

2014-04-01

10

Focusing Light through Random Photonic Media by Binary Amplitude Modulation  

CERN Document Server

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 ...

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

2011-01-01

11

Phase lag in the amplitude modulated magnetic resonance  

Science.gov (United States)

Response of a magnetic spin system to the amplitude modulated radiofrequency field is studied. Spin system is assumed to obey Bloch equations. For a spin system resonant at Larmor frequency ? 0, calculations demonstrate how the phase lags ? ? and ? z, of magnetization components M x, M y and M z occur and how sensitive they are to the relaxation properties of the system. Relative to Larmor frequency the angular frequency of the amplitude modulation, ??? 0, is very low, at the same time it is comparable to the relaxation rates of the spins. With reference to the analytical solution of a damped harmonic oscillator a simple formula tan? ?=T 2? describes the magnitude of the phase lag ? ? as a function of relaxation time T 2.

Krupski, Marcin; Sczaniecki, Pawe? B.

2001-08-01

12

Coherent amplitude modulation of electron-beam-driven Langmuir waves  

Directory of Open Access Journals (Sweden)

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

K. Baumgärtel

2013-04-01

13

Spatial horizons in amplitude and frequency modulation atomic force microscopy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In dynamic atomic force microscopy (AFM) the cantilever is vibrated and its dynamics are monitored to probe the sample with nanoscale and atomic resolution. Amplitude and frequency modulation (AM and FM) atomic force microscopy have established themselves as the most powerful, robust and reliable techniques in the field. Nevertheless, it is still debatable whether one or the other technique is preferred in a given medium or experiment. Here, we quantitatively establish the limi...

Font Teixido?, Josep; Santos Herna?ndez, Sergio; Barcons Xixons, Vi?ctor; Thomson, Neil H.; Verdaguer, Albert; Chiesa, Matteo

2012-01-01

14

Oblique amplitude modulation of dust-acoustic plasma waves  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Theoretical and numerical studies are presented of the nonlinear amplitude modulation of dust-acoustic (DA) waves propagating in an unmagnetized three component, weakly-coupled, fully ionized plasma consisting of electrons, positive ions and charged dust particles, considering perturbations oblique to the carrier wave propagation direction. The stability analysis, based on a nonlinear Schroedinger-type equation (NLSE), shows that the wave may become unstable; the stability c...

Kourakis, I.; Shukla, P. K.

2004-01-01

15

Research of frequency modulation to amplitude modulation with multi-frequency modulation  

Science.gov (United States)

For better performance of laser coupling in inertial confinement fusion (ICF), beam shaping of the focus spot is required. Among all the beam smoothing methods, the multi frequency modulation smoothing by spectral dispersion (MultiFM-SSD) proposed by LLE has the advantages of the faster smoothing and better operability. Strong frequency modulation to amplitude modulation conversion(FM-to-AM) will take place because of the complex spectrum imposed by the multi frequency modulators applied in the Multi FM-SSD method. The FM-to-AM effect is studied with numerical simulation including the polarization mode dispersion and group velocity dispersion. The results reveal that the modulation frequencies and bandwidths of multi modulators will influence the contrast degree of the FM-to-AM effect. The compensation of the FM-to-AM with arbitrary waveform generator (AWG) is also numerically simulated. The FM-to-AM effect is effectively suppressed, i.e. the non-uniformity of the pulse decreases substantially, by applying multiple intensity and phase compensation (the compensation function is obtained via G-S algorithm).

Zhou, Yuliang; Zhan, Sui; Geng, Yuanchao; Liu, Lanqin; Xu, Lixin; Ming, Hai

2013-12-01

16

Amplitude modulation of atomic wave functions. Final report  

Energy Technology Data Exchange (ETDEWEB)

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 {micro}m 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.

NONE

1998-11-01

17

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

18

Longitudinal tracking with phase and amplitude modulated rf  

International Nuclear Information System (INIS)

Synchrotron motion was induced by phase shifting the rf of the Indiana University Cyclotron Facility (IUCF) cooler-synchrotron. The resulting coherent-bunch motion was tracked in longitudinal phase space for as many as 700,000 turns, or for over 350 synchrotron oscillations. Results of recent experimental studies of longitudinal motion in which the rf phase and amplitude were harmonically modulated are also presented. Comparisons of experimental data with numerical simulations, assuming independent particle motion, are made. Observed multiparticle effects are also discussed

19

Modulated Amplitude Waves in Bose-Einstein Condensates  

CERN Document Server

We analyze spatio-temporal structures in the Gross-Pitaevskii equation to study the dynamics of quasi-one-dimensional Bose-Einstein condensates (BECs) with mean-field interactions. A coherent structure ansatz yields a parametrically forced nonlinear oscillator, to which we apply Lindstedt's method and multiple scale perturbation theory to determine the dependence of the intensity of periodic orbits (``modulated amplitude waves'') on their wave number. We explore BEC band structure in detail using Hamiltonian perturbation theory and supporting numerical simulations.

Porter, M A; Porter, Mason A.; Cvitanovic, Predrag

2003-01-01

20

Longitudinal Tracking with Phase and Amplitude Modulated RF  

CERN Document Server

Synchrotron motion was induced by phase shifting the rf of the Indiana University Cyclotron Facility (IUCF) cooler-synchrotron. The resulting coherent-bunch motion was tracked in longitudinal phase space for as many as 700,000 turns, or for over 350 synchrotron oscillations. Results of recent experimental studies of longitudinal motion in which the rf phase and amplitude were harmonically modulated are also presented. Comparisons of experimental data with numerical simulations, assuming independent particle motion, are made. Observed multiparticle effects are also discussed.

Minty, Michiko G

2003-01-01

 
 
 
 
21

Study of an electro-optic modulator capable of generating simultaneous amplitude and phase modulations  

CERN Document Server

We report on the analysis and prototype-characterization of a dual-electrode electro-optic modulator that can generate both amplitude and phase modulations with a selectable relative phase, termed a universally tunable modulator (UTM). All modulation states can be reached by tuning only the electrical inputs, facilitating real-time tuning, and the device is shown to have good suppression and stability properties. A mathematical analysis is presented, including the development of a geometric phase representation for modulation. The experimental characterization of the device shows that relative suppressions of 38 dB, 39 dB and 30 dB for phase, single-sideband and carrier-suppressed modulations, respectively, can be obtained, as well as showing the device is well-behaved when scanning continuously through the parameter space of modulations. Uses for the device are discussed, including the tuning of lock points in optical locking schemes, single sideband applications, modulation fast-switching applications, and ...

Cusack, B J; Shaddock, D A; Gray, M B; Lam, P K; Whitcomb, S E; Cusack, Benedict J; Gray, Malcolm B; Lam, Ping Koy; Shaddock, Daniel A; Sheard, Benjamin S; Whitcomb, Stan E

2003-01-01

22

Research proposal on : amplitude modulated reflectometry system for JET divertor  

International Nuclear Information System (INIS)

Amplitude Modulated reflectometry is presented here as a tool for density profile measurements in the JET divertor plasmas. One of the main problems which has been presented 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 bring to fringe jumps' in the phase signal, which are a big problem when the phase values are much larger than 2 pi. The conditions in the JET divertor plasmas: plasma geometry, access and long oversized broad-band waveguide paths makes very difficult the phase measurements at the millimeter wave range. AM reflectometry is to some extension an intermediate solution between the classical phase delay reflectometry, so far applied to small distances, and the time domain reflectometry, used for ionospheric studies and recently also proposed for fusion plasma. the main advantage is to allow the use of millimeter wave reflectometry with moderate phase shifts (approx 2 pi). (author)

23

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

Science.gov (United States)

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

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

2014-04-01

24

On the frequency spectrum of Amplitude Modulation Following Responses.  

Science.gov (United States)

Objective detection of Amplitude Modulation Following Responses (AMFR) is based on statistics applied after signal transformation from the time to the frequency domain by means of Discrete Fourier Transformation. In theory the frequency resolution of such transformation depends only on the analysed time window. In practise frequency resolution is also limited by the error caused by minimal difference between the clocks used for stimulus generation and Analogue/Digital-conversion. Small differences in clock frequencies may cause a spread of energy to neighbouring bins. In order to avoid this error we derived the sample clock for the A/D-conversion from the stimulator clock. By means of this technique the frequency structure of the AMFR was investigated. It is shown that if technical induced errors are excluded, the energy of the AMFR-response is limited to a very narrow frequency band. No physiologically induced disturbances of the phase locking of the AMFR to the modulation frequency could be observed. Additionally it is demonstrated that an increase of frequency resolution leads to an improved signal to noise ratio similar to the increase of averages in the time domain. PMID:10990018

Pethe, J; Hocke, T; Mühler, R; von Specht, H

2000-01-01

25

Frequency modulation to amplitude modulation conversion of different broadband pulses propagating in Nd-glass amplifiers  

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)

26

Modifications and lithography on iridovirus surface using amplitude modulated nanolithography  

Science.gov (United States)

The usage of electrostatic force on nanoscale proved to be very effective for pattering nanostructures in 20-30-nm thin polymer films using biased atomic force microscope tip (AFM) [1,2]. Similar approach can be applied to biological objects of several hundred nanometers size deposited on a smooth conductive substrate. This study demonstrates the first attempt modifying an iridovirus surface using amplitude-modulated nanolithography (AF-AFMEN) [2]. With this technique we mark an individual virus capsule by applying -10-30 V to an AFM conductive tip tapping the virus. The marks on the virus surface represent raises of 1-5 nm height. Similar to polymer molecules, the dense layer of iridovirus was subjected to AF-AFMEN technique producing distinct nanostructures (10-50 nm wide) formed of virus electrostatically attracted to the tip. Several physical reasons responsible for the virus manipulation and marking will be discussed. 1. S.F. Lyuksyutov, R.A. Vaia, P.B. Paramonov, S. Juhl, L. Waterhouse, R.M. Ralich, G. Sigalov, and E. Sancaktar, Nature Materials 2, 468 (2003) 2. S.F. Lyuksyutov, R.A. Vaia, P.B. Paramonov, and S. Juhl, Appl. Phys. Lett. 83, 4405 (2003)

Lyuksyutov, Sergei; Paramonov, Pavel; Mayevska, Olga; Umemura, Kazuo; Vaia, Richard; Juhl, Shane; Waterhouse, Lynn

2004-04-01

27

Vocal production mechanisms in the budgerigar (Melopsittacus undulatus): the presence and implications of amplitude modulation.  

Science.gov (United States)

In this paper acoustic evidence is presented for the presence of amplitude modulation in budgerigar (Melopsittacus undulatus) contact calls and learned English vocalizations. Previously, acoustic analyses of budgerigar vocalizations have consisted solely of visual inspection of spectrograms or power spectra (derived from Fourier transformation). Such analyses have led researchers to conclude that budgerigar vocalizations are primarily frequency-modulated, harmonic vocalizations. Although budgerigar calls have been shown to contain regions that are modulated in amplitude, the implications of this fact have been largely ignored. Amplitude modulation, the nonlinear interaction between two separate signals that results in the creation of new, heterodyne (sum and difference) frequencies, can produce a very complex Fourier spectrum that may resemble that produced by a harmonic vocalization. In this paper, the acoustic principles necessary for identifying amplitude modulation present in signals are outlined, and followed by data demonstrating that amplitude modulation is a prominent feature not only of natural budgerigar contact calls, but also of their learned English vocalizations. It is illustrated how analyzing a vocalization that contains amplitude modulation as if it were harmonic can result in misinterpretations of the acoustic and physical properties of the sound and sound source. The implications of amplitude modulation for studies of the ontogenetic, physical, and neural basis of budgerigar vocalizations are discussed, and a potential model for how the budgerigar syrinx may function to produce amplitude modulation is proposed. PMID:10420639

Lavenex, P B

1999-07-01

28

Auditory Cortex Phase Locking to Amplitude-Modulated Cochlear Implant Pulse Trains  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cochlear implant speech processors transmit temporal features of sound as amplitude modulation of constant-rate electrical pulse trains. This study evaluated the central representation of amplitude modulation in the form of phase-locked firing of neurons in the auditory cortex. Anesthetized pigmented guinea pigs were implanted with cochlear electrode arrays. Stimuli were 254 pulse/s (pps) trains of biphasic electrical pulses, sinusoidally modulated with frequencies of 10–64 Hz and modulatio...

Middlebrooks, John C.

2008-01-01

29

Encoding and decoding amplitude-modulated cochlear implant stimuli—a point process analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cochlear implant speech processors stimulate the auditory nerve by delivering amplitude-modulated electrical pulse trains to intracochlear electrodes. Studying how auditory nerve cells encode modulation information is of fundamental importance, therefore, to understanding cochlear implant function and improving speech perception in cochlear implant users. In this paper, we analyze simulated responses of the auditory nerve to amplitude-modulated cochlear implant stimuli using a point process m...

Goldwyn, Joshua H.; Shea-brown, Eric; Rubinstein, Jay T.

2010-01-01

30

Trellis-coded pulse amplitude modulation for indoor visible light communication  

Science.gov (United States)

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.

Wang, Yu; Yang, Aiying; Wu, Yongsheng; Feng, Lihui; Sun, Yu-nan; Li, Yankun

2013-12-01

31

Beating frequency and amplitude modulation of the piano tone due to coupling of tones  

Science.gov (United States)

The influence on a piano tone from weak coexcitation of damped adjacent tones due to coupling via the bridge is studied. The frequency and amplitude modulation of the sound resulting from coexcitation of one strong and one or two weak tones is analyzed. One weak tone causes frequency and amplitude modulation of the sound, and two weak tones produce beating frequency and amplitude modulation, where the beatings of the two modulations are of opposite phase. By digital recording of the sound of piano tones, the appearance of these phenomena is verified. The audibility of the observed frequency and amplitude modulation is discussed in terms of previously determined detection thresholds. The beating character of both frequency and amplitude modulations, however, distinguishes the phenomena from those previously studied and prompts further psychoacoustic investigations. It is shown that detuning of unison strings may significantly increase the frequency deviation of the frequency modulation in conjunction with affected amplitude modulation. The modulatory effects of coupling to adjacent tones therefore may possibly be utilized in the tuning process. A coupling of tones analogous to the situation in a piano may arise in other stringed musical instruments transferring string vibrations to a soundboard via a bridge. .

Cartling, Bo

2005-04-01

32

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

Science.gov (United States)

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

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

2007-06-01

33

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

International Nuclear Information System (INIS)

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

34

Modulation rate discrimination using half-wave rectified and sinusoidally amplitude modulated stimuli in cochlear-implant users  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Detection and modulation rate discrimination were measured in cochlear-implant users for pulse-trains that were either sinusoidally amplitude modulated or were modulated with half-wave rectified sinusoids, which in acoustic hearing have been used to simulate the response to low-frequency temporal fine structure. In contrast to comparable results from acoustic hearing, modulation rate discrimination was not statistically different for the two stimulus types. The results suggest that, in contra...

Kreft, Heather A.; Oxenham, Andrew J.; Nelson, David A.

2010-01-01

35

An amplitude modulated laser system for distance and displacement measurement  

Science.gov (United States)

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

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

1986-01-01

36

Smooth Pursuit Saccade Amplitude Modulation During Exposure to Microgravity  

Science.gov (United States)

Russian investigators have reported changes in pursuit tracking of a vertically moving point stimulus during space flight. Early in microgravity, changes were manifested by decreased eye movement amplitude (undershooting) and the appearance of correction saccades. As the flight progressed, pursuit of the moving point stimulus deteriorated while associated saccadic movements were unchanged. Immediately postflight there was an improved execution of active head movements indicating that the deficiencies in pursuit function noted in microgravity may be of central origin. In contrast, tests of two cosmonauts showed that horizontal and vertical smooth pursuit were unchanged inflight. However, results of corresponding saccadic tasks showed a tendency toward the overshooting of a horizontal target early inflight with high accuracy developing later inflight, accompanied by an increased saccade velocity and a trend toward decreased saccade latency. Based on these equivocal results, we have further investigated the effects of space flight on the smooth pursuit mechanism during and after short duration flight, and postflight on returning MIR crewmembers. Sinusoidal target movement was presented horizontally at frequencies of 0.33 and 1.0 Hz. Subjects were asked to perform two trials for each stimulus combination: (1) moving eyes-only (EO) and (2) moving eyes and head (EH) with the target motion. Peak amplitude was 30 deg for 0.33 Hz trials and 15 deg for the 1.0 Hz trials. The relationship between saccade amplitude and peak velocity were plotted as a main sequence for each phase of flight, and linear regression analysis allowed us to determine the slope of each main sequence plot. The linear slopes were then combined for each flight phase for each individual subject. The main sequence for both EO and EH trials at both the 0.33 and 1.0 Hz frequencies during flight for the short duration flyers showed a reduction in saccade velocity and amplitude when compared to the preflight main sequence . This difference in the regression slopes between flight phase, head/eye condition (EO or EH), and pursuit target frequency was observed across all subjects (statistically significant at the psaccade amplitude and peak velocity to increase during the postflight testing. This tendency had vanished by R+ 1. Of particular interest was the redistribution of saccades during the latter stages of the flight and immediately postflight in the EO condition. At the 1.0 Hz frequency the saccades tended to be clustered near the lowest target velocity. It was also interesting to note that gaze performance (eye in skull + head in space) was consistently better during the EH condition; a finding also observed by our Russian colleagues. As the results of the long duration flight become available we expect that they will not only show that postflight effects will be similar to those observed during the short duration flights, but will also last for a greater period of time following flight. It is not clear what mechanism is responsible for the decreased peak saccadic velocity during flight unless the change is related to the control of retinal slip. For example, it is possible that saccades will tend to initially undershoot their targets by a small percentage and these saccades are then followed, if vision is available, by a small augmenting corrective saccade. It has been postulated that the functional significance of this undershooting tendency is to maintain the spatial representation of the target on the same side of the fovea (as opposedo racing across the fovea) and hence in the same cerebral hemisphere that initiated the primar

Reschke, M. F.; Kozlovskaya, I. B.; Sayenko, D. G.; Sayenko, I.; Somers, J. T.; Paloski, W. H.

2002-01-01

37

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

Science.gov (United States)

We study amplitude-modulated waves, e.g., wave packets in one dimension, overtarget spirals and superspirals in two dimensions, under mixed-mode oscillatory conditions in a three-variable reaction-diffusion model. New transition zones, not seen in the homogeneous system, are found, in which periodic transitions occur between local 1(N-1) and 1(N) oscillations. Amplitude-modulated complex patterns result from periodic transition between (N?-?1)-armed and N-armed waves. Spatial recurrence rates provide a useful guide to the stability of these modulated patterns. PMID:24985423

Tang, Xiaodong; He, Yuxiu; Epstein, Irving R; Wang, Qun; Wang, Shaorong; Gao, Qingyu

2014-06-01

38

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-06-15

39

Timbral Sharpness and Modulations in Frequency and Amplitude: Implications for the Fusion of Musical Sounds.  

Science.gov (United States)

The fusion of musical voices is an important aspect of musical blend, or the mixing of individual sounds. Yet, little research has been done to explicitly determine the factors involved in fusion. In this study, the similarity of timbre and modulation were examined for their contribution to the fusion of sounds. It is hypothesized that similar timbres will fuse better than dissimilar timbres, and, voices with the same kind of modulation will fuse better than voices of different modulations. A perceptually-based measure, known as sharpness was investigated as a measure of timbre. The advantages of using sharpness are that it is based on hearing sensitivities and masking phenomena of inner ear processing. Five musical instrument families were digitally recorded in performances across a typical playing range at two extreme dynamic levels. Analyses reveal that sharpness is capable of uncovering subtle changes in timbre including those found in musical dynamics, instrument design, and performer-specific variations. While these analyses alone are insufficient to address fusion, preliminary calculations of timbral combinations indicate that sharpness has the potential to predict the fusion of sounds used in musical composition. Three experiments investigated the effects of modulation on the fusion of a harmonic major sixth interval. In the first experiment using frequency modulation, stimuli varied in deviation about a mean fundamental frequency and relative modulation phase between the two tones. Results showed smaller frequency deviations promoted fusion and relative phase differences had a minimal effect. In a second experiment using amplitude modulation, stimuli varied in deviation about a mean amplitude level and relative phase of modulation. Results showed smaller amplitude deviations promoted better fusion, but unlike frequency modulation, relative phase differences were also important. In a third experiment, frequency modulation, amplitude modulation and mixed modulation were arranged in all possible voicings. Results showed frequency modulation in the lower voice and less variance in amplitude envelopes contributed to an increase in fusion. The theory that similar modulations would promote better fusion was only marginally supported. For these experiments, results revealed differences depending on modulation type and that a lesser amount of modulation fosters greater fusion.

Goad, Pamela Joy

40

Effects of low-frequency biasing on spontaneous otoacoustic emissions: Amplitude modulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The dynamic effects of low-frequency biasing on spontaneous otoacoustic emissions (SOAEs) were studied in human subjects under various signal conditions. Results showed a combined suppression and modulation of the SOAE amplitudes at high bias tone levels. Ear-canal acoustic spectra demonstrated a reduction in SOAE amplitude and growths of sidebands while increasing the bias tone level. These effects varied depending on the relative strength of the bias tone to a particular SOAE. The SOAE magn...

Bian, Lin; Watts, Kelly L.

2008-01-01

 
 
 
 
41

Auditory cortex phase locking to amplitude-modulated cochlear implant pulse trains.  

Science.gov (United States)

Cochlear implant speech processors transmit temporal features of sound as amplitude modulation of constant-rate electrical pulse trains. This study evaluated the central representation of amplitude modulation in the form of phase-locked firing of neurons in the auditory cortex. Anesthetized pigmented guinea pigs were implanted with cochlear electrode arrays. Stimuli were 254 pulse/s (pps) trains of biphasic electrical pulses, sinusoidally modulated with frequencies of 10-64 Hz and modulation depths of -40 to -5 dB re 100% (i.e., 1-56.2% modulation). Single- and multiunit activity was recorded from multi-site silicon-substrate probes. The maximum frequency for significant phase locking (limiting modulation frequency) was >or=60 Hz for 42% of recording sites, whereas phase locking to pulses of unmodulated pulse trains rarely exceeded 30 pps. The strength of phase locking to frequencies >or=40 Hz often varied nonmonotonically with modulation depth, commonly peaking at modulation depths around -15 to -10 dB. Cortical phase locking coded modulation frequency reliably, whereas a putative rate code for frequency was confounded by rate changes with modulation depth. Group delay computed from the slope of mean phase versus modulation frequency tended to increase with decreasing limiting modulation frequency. Neurons in cortical extragranular layers had lower limiting modulation frequencies than did neurons in thalamic afferent layers. Those observations suggest that the low-pass characteristic of cortical phase locking results from intracortical filtering mechanisms. The results show that cortical neurons can phase lock to modulated electrical pulse trains across the range of modulation frequencies and depths presented by cochlear implant speech processors. PMID:18367697

Middlebrooks, John C

2008-07-01

42

Propagation and Ion Dynamics of Waves in Amplitude Modulated Helicon Plasmas  

International Nuclear Information System (INIS)

A helicon source is driven with amplitude modulated RF at modulation frequencies near the ion cyclotron frequency in the VINETA device. In response to the modulation propagating electromagnetic waves are found, whose dispersion differs significantly from linear wave dispersion theory. This indicates that the observed waves are generated by non-linear wave coupling of the helicon waves with a second strongly damped or evanescent wave. Laser induced fluorescence measurements reveal a local increase of the ion temperature at the minimum of the modulation drive

43

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

International Nuclear Information System (INIS)

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

44

Micromachining of amplitude and phase modulated reflective computer generated hologram patterns in silicon  

International Nuclear Information System (INIS)

Silicon has been machined on lateral resolutions of micrometers and on depth resolutions of nanometers using a recently-developed process based on ion irradiation and electrochemical anodisation. Here we investigate its use as a recording medium for computer generated hologram patterns. We describe the fabrication of both amplitude and phase binary modulated reflective computer generated hologram patterns on a silicon surface with pixel sizes of 5 ?m. We further discuss the use of micromachined silicon to variably modulate both amplitude and phase in a continuous, rather than a binary fashion.

45

Human Neuromagnetic Steady-State Responses to Amplitude-Modulated Tones, Speech, and Music  

Science.gov (United States)

Objectives: Auditory steady-state responses that can be elicited by various periodic sounds inform about subcortical and early cortical auditory processing. Steady-state responses to amplitude-modulated pure tones have been used to scrutinize binaural interaction by frequency-tagging the two ears’ inputs at different frequencies. Unlike pure tones, speech and music are physically very complex, as they include many frequency components, pauses, and large temporal variations. To examine the utility of magnetoencephalographic (MEG) steady-state fields (SSFs) in the study of early cortical processing of complex natural sounds, the authors tested the extent to which amplitude-modulated speech and music can elicit reliable SSFs. Design: MEG responses were recorded to 90-s-long binaural tones, speech, and music, amplitude-modulated at 41.1 Hz at four different depths (25, 50, 75, and 100%). The subjects were 11 healthy, normal-hearing adults. MEG signals were averaged in phase with the modulation frequency, and the sources of the resulting SSFs were modeled by current dipoles. After the MEG recording, intelligibility of the speech, musical quality of the music stimuli, naturalness of music and speech stimuli, and the perceived deterioration caused by the modulation were evaluated on visual analog scales. Results: The perceived quality of the stimuli decreased as a function of increasing modulation depth, more strongly for music than speech; yet, all subjects considered the speech intelligible even at the 100% modulation. SSFs were the strongest to tones and the weakest to speech stimuli; the amplitudes increased with increasing modulation depth for all stimuli. SSFs to tones were reliably detectable at all modulation depths (in all subjects in the right hemisphere, in 9 subjects in the left hemisphere) and to music stimuli at 50 to 100% depths, whereas speech usually elicited clear SSFs only at 100% depth. The hemispheric balance of SSFs was toward the right hemisphere for tones and speech, whereas SSFs to music showed no lateralization. In addition, the right lateralization of SSFs to the speech stimuli decreased with decreasing modulation depth. Conclusions: The results showed that SSFs can be reliably measured to amplitude-modulated natural sounds, with slightly different hemispheric lateralization for different carrier sounds. With speech stimuli, modulation at 100% depth is required, whereas for music the 75% or even 50% modulation depths provide a reasonable compromise between the signal-to-noise ratio of SSFs and sound quality or perceptual requirements. SSF recordings thus seem feasible for assessing the early cortical processing of natural sounds. PMID:24603544

Parkkonen, Lauri; Hari, Riitta

2014-01-01

46

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

Directory of Open Access Journals (Sweden)

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

Miriam Jaafar

2012-04-01

47

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

Science.gov (United States)

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

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

2011-10-01

48

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

CERN Document Server

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

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

2009-01-01

49

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

Science.gov (United States)

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

Bowman, Dominic M.; Kurtz, Donald W.

2014-10-01

50

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

Science.gov (United States)

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

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

2014-09-01

51

Radar transponder operation with compensation for distortion due to amplitude modulation  

Science.gov (United States)

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.

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

2011-01-04

52

Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light  

Science.gov (United States)

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 or the amplitude 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 frequency ?L (either by DC or phase sensitive detection at harmonics q of the modulation frequency ?mod) of the transmitted light are expressed in terms of the Fourier coefficients of the modulation function. Our approach is based on an atomic multipole moment representation that is valid for spin-oriented atomic states with arbitrary angular momentum F in the low light power limit. We find excellent quantitative agreement with an experimental case study using (square-wave) amplitude-modulated light.

Gruji?, Z. D.; Weis, A.

2013-07-01

53

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.

54

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

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.

Ghaffar, Farhan Abdul

2012-09-30

55

After stroke bidirectional modulation of soleus stretch reflex amplitude emerges during rhythmic arm cycling  

Directory of Open Access Journals (Sweden)

Full Text Available Objectives: After stroke a typical presentation is exaggerated stretch reflexes (SR on the more affected (MA side. The present study evaluated the contribution of presynaptic inhibition (PSI induced by arm cycling and homosynaptic depression (HD to the modulation of hyperreflexia at the ankle after stroke. Possible asymmetry of these effects between the MA and less affected (LA legs was also assessed. Methods: Soleus SR was conditioned by: arm cycling at 1Hz (to increase Ia PSI; or, a preceding conditioning tendon tap applied 1 s before the test stimulus (to induce HD. The extent of conditioning effects was compared between the MA and the LA legs. Results: For both MA and LA legs, rhythmic arm movement induced a bidirectional effect in different participants, either increasing or decreasing SR amplitude (p< 0.05. HD had a significant effect in both legs (p< 0.05, however, the effect of both a previous muscle stretch and arm cycling was not different between the MA and the LA legs. Conclusion: Our data reveal a bidirectional reflex modulation induced by arm cycling that produced facilitation in some and suppression in other participants after stroke. Relative SR amplitude modulation did not differ between the LA and MA legs. We speculate that alterations in SR amplitude modulation after stroke may reflect specific changes in both presynaptic afferent transmission mechanisms and fusimotor control. Significance: The present findings open new perspectives on the characterization of pathophysiology of stroke during the performance of functionally relevant motor tasks.

RinaldoAndréMezzarane

2014-03-01

56

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

CERN Document Server

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

Goorden, Sebastianus A; Mosk, Allard P

2014-01-01

57

A method of measuring the amplitude-modulated vacuum field near a conducting mirror  

Science.gov (United States)

Electromagnetic fields of the vacuum mode near a conducting mirror are modified with respect to those in free space, with their amplitudes having a sinusoidal spatial dependence from the mirror. Therefore if we combine this spatially amplitude-modulated vacuum field mode and intense coherent light with a beam splitter, we may detect this fluctuation of the vacuum mode in a homodyne detection scheme. It will give a new method to produce squeezed states of light with a single mirror placed close to an unused port of a beam splitter. We show that the amplitude fluctuation of the combined light can be reduced by a factor of 2 below that of the coherent light. We also discuss the limitations due to the finite line width of the laser and the effective absorption length of the photodiodes.

Youn, Sun-Hyun; Lee, Jai-Hyung; Chang, Joon-Sung

1994-01-01

58

Improving the performance of bright quantum dot single photon sources using amplitude modulation  

CERN Document Server

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.

Ates, Serkan; Gulinatti, Angelo; Rech, Ivan; Badolato, Antonio; Srinivasan, Kartik

2012-01-01

59

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

Science.gov (United States)

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

Trosin, Barry James

2007-01-01

60

Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation  

DEFF Research Database (Denmark)

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.

Sosnovtseva, Olga; Pavlov, A.N.

2004-01-01

 
 
 
 
61

Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light  

CERN Document Server

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...

Gruji?, Z D

2013-01-01

62

Propagation properties of apertured laser beams with amplitude modulations and phase fluctuations through atmospheric turbulence  

Science.gov (United States)

The propagation properties of apertured laser beams with amplitude modulations (AMs) and phase fluctuations (PFs) through atmospheric turbulence are studied in detail both analytically and numerically. The analytical expressions for the average intensity, power in the bucket ( PIB) and Strehl ratio ( S R ) of apertured laser beams with AMs and PFs propagating through atmospheric turbulence are derived. It is found that the worse the phase fluctuation and the higher the amplitude modulation are, the less laser beams are affected by turbulence. Furthermore, apertured Gaussian beams are more sensitive to turbulence than apertured laser beams with AMs and PFs. The average intensity of apertured laser beams with AMs and PFs may be even larger than that of apertured Gaussian beams due to turbulence. In particular, the influence of turbulence on the average maximum intensity of apertured laser beams with PFs and AMs may become serious if an unsuitable truncated parameter is chosen, which should be avoided in practice.

Ji, X.; Li, X.

2011-07-01

63

Vibrotactile Sensory Substitution for Object Manipulation: Amplitude versus Pulse Train Frequency Modulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Incorporating sensory feedback with prosthetic devices is now possible, but the optimal methods of providing such feedback are still unknown. The relative utility of amplitude and pulse train frequency modulated stimulation paradigms for providing vibrotactile feedback for object manipulation was assessed in 10 participants. The two approaches were studied during virtual object manipulation using a robotic interface as a function of presentation order and a simultaneous cognitive load. Despit...

Stepp, Cara E.; Matsuoka, Yoky

2012-01-01

64

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

Energy Technology Data Exchange (ETDEWEB)

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

Kirschstein, Anika; Herbst, Christian; Riedel, Kerstin; Carella, Michela; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai [Fritz Lipmann Institute, Research Group Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany)], E-mail: raman@fli-leibniz.de

2008-04-15

65

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

International Nuclear Information System (INIS)

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

66

Fuzzy control with amplitude/pulse-width modulation of nerve electrical stimulation for muscle force control.  

Science.gov (United States)

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

Lin, C-C K; Liu, W-C; Chan, C-C; Ju, M-S

2012-04-01

67

Ultrafast modulation of polarization amplitude by terahertz fields in electronic-type organic ferroelectrics.  

Science.gov (United States)

Ferroelectrics sometimes show large electro-optical and non-linear optical effects, available for polarization rotation and frequency conversion of light, respectively. If the amplitude of ferroelectric polarization is modulated in the picosecond time domain, terahertz repetition of optical switching via electro-optical and non-linear optical effects would be achieved. Here we show that polarization amplitude can be rapidly modulated by a terahertz electric field in an organic ferroelectric, tetrathiafulvalene-p-chloranil (TTF-CA). In this compound, alternately stacked donor (TTF) and acceptor (CA) molecules are dimerized via the spin-Peierls mechanism, and charge transfer within each dimer results in a new type of ferroelectricity called electronic-type ferroelectricity. Using a terahertz field, the intradimer charge transfer is strongly modulated, producing a subpicosecond change in the macroscopic polarization, which is demonstrated by transient reflectivity and second-harmonic generation measurements. Subsequently, coherent oscillation of the dimeric molecular displacements occur, which is explained by the modulation of the spin moment of each molecule. PMID:24131938

Miyamoto, Tatsuya; Yada, Hiroyuki; Yamakawa, Hiromichi; Okamoto, Hiroshi

2013-01-01

68

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

Directory of Open Access Journals (Sweden)

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. .

Ramkumar Subburam

2009-01-01

69

Heteronuclear J cross-polarisation in liquids using amplitude and phase modulated mixing sequences  

Energy Technology Data Exchange (ETDEWEB)

The design of mixing sequences for heteronuclear J cross-polarisation in the liquid state has been examined employing supercycles of amplitude/phase modulated RF pulses. The Fourier coefficients defining the modulation profiles of the pulses were optimised numerically so as to achieve efficient magnetisation transfer within the desired range of resonance offsets. A variety of supercycles, pulsewidths and RF field strengths were considered in implementing heteronuclear anisotropic and isotropic mixing sequences. The coherence transfer characteristics of the sequences obtained were evaluated by numerical simulations. The experimental performances of the sequences were tested by measurements carried out on a moderate sized protein at 750 MHz. The results presented demonstrate that the approach adopted in this study can be employed effectively to tailor, as per the experimental requirements and constraints, the RF-field modulation profiles of the pulses constituting the mixing scheme for generating heteronuclear J cross-polarisation sequences.

Kirschstein, Anika; Herbst, Christian; Riedel, Kerstin; Carella, Michela; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai [Leibniz Institute for Age Research, Fritz Lipmann Institute, Research group Biomolecular NMR spectroscopy (Germany)], E-mail: raman@fli-leibniz.de

2008-04-15

70

Heteronuclear J cross-polarisation in liquids using amplitude and phase modulated mixing sequences  

International Nuclear Information System (INIS)

The design of mixing sequences for heteronuclear J cross-polarisation in the liquid state has been examined employing supercycles of amplitude/phase modulated RF pulses. The Fourier coefficients defining the modulation profiles of the pulses were optimised numerically so as to achieve efficient magnetisation transfer within the desired range of resonance offsets. A variety of supercycles, pulsewidths and RF field strengths were considered in implementing heteronuclear anisotropic and isotropic mixing sequences. The coherence transfer characteristics of the sequences obtained were evaluated by numerical simulations. The experimental performances of the sequences were tested by measurements carried out on a moderate sized protein at 750 MHz. The results presented demonstrate that the approach adopted in this study can be employed effectively to tailor, as per the experimental requirements and constraints, the RF-field modulation profiles of the pulses constituting the mixing scheme for generating heteronuclear J cross-polarisation sequences

71

Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers  

International Nuclear Information System (INIS)

Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized 208-210Fr ion beams at beam energies of 5 keV and intensities of 105 s-1. Efficient neutralization (?80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

72

Determination of amplitude and frequency modulations from the Orsay synchrocyclotron R.F. voltage. Shape of the rotative condenser blades  

International Nuclear Information System (INIS)

The correspondance between amplitude and frequency modulations for a synchrocyclotron R.F. Voltage is firstly established. Optimal shapes are determined for these modulations for the Orsay synchrocyclotron. Shape of the rotative condenser static blades is then calculated to obtain the desired frequency modulation. Comparison is made between expected and obtained data. Values of working parameters are then proposed

73

Phase dependent modulation of tremor amplitude in essential tremor through thalamic stimulation.  

Science.gov (United States)

High frequency deep brain stimulation of the thalamus can help ameliorate severe essential tremor. Here we explore how the efficacy, efficiency and selectivity of thalamic deep brain stimulation might be improved in this condition. We started from the hypothesis that the effects of electrical stimulation on essential tremor may be phase dependent, and that, in particular, there are tremor phases at which stimuli preferentially lead to a reduction in the amplitude of tremor. The latter could be exploited to improve deep brain stimulation, particularly if tremor suppression could be reinforced by cumulative effects. Accordingly, we stimulated 10 patients with essential tremor and thalamic electrodes, while recording tremor amplitude and phase. Stimulation near the postural tremor frequency entrained tremor. Tremor amplitude was also modulated depending on the phase at which stimulation pulses were delivered in the tremor cycle. Stimuli in one half of the tremor cycle reduced median tremor amplitude by ?10%, while those in the opposite half of the tremor cycle increased tremor amplitude by a similar amount. At optimal phase alignment tremor suppression reached 27%. Moreover, tremor amplitude showed a non-linear increase in the degree of suppression with successive stimuli; tremor suppression was increased threefold if a stimulus was preceded by four stimuli with a similar phase relationship with respect to the tremor, suggesting cumulative, possibly plastic, effects. The present results pave the way for a stimulation system that tracks tremor phase to control when deep brain stimulation pulses are delivered to treat essential tremor. This would allow treatment effects to be maximized by focussing stimulation on the optimal phase for suppression and by ensuring that this is repeated over many cycles so as to harness cumulative effects. Such a system might potentially achieve tremor control with far less power demand and greater specificity than current high frequency stimulation approaches, and may lower the risk for tolerance and rebound. PMID:24038075

Cagnan, Hayriye; Brittain, John-Stuart; Little, Simon; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Hariz, Marwan; Joint, Carole; Fitzgerald, James; Green, Alexander L; Aziz, Tipu; Brown, Peter

2013-10-01

74

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

Science.gov (United States)

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.

Ramos, Jorge R.

2014-07-01

75

Subharmonic excitation in amplitude modulation atomic force microscopy in the presence of adsorbed water layers  

Energy Technology Data Exchange (ETDEWEB)

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.

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

76

Intermodal interference induced significant frequency modulation to amplitude modulation conversion in a broadband large-mode-area fiber laser.  

Science.gov (United States)

The conversion of the FM-to-AM effect induced by intermodal interference in the broadband large-mode-area (LMA) fiber laser was first investigated theoretically and experimentally. The numerical simulation results show that the spectrum transfer functions are different at different positions of the LMA fiber end face owing to the intermodal interference, so the output broadband pulses are different. We attain the similar results in the experiment when measuring the output pulse with the single mode fiber sampling oscilloscope. Whereas there is no amplitude modulation for the output pulse when measured by the bulk detector owing to the orthogonal characteristic of the eigenmodes. PMID:21478980

Li, Jing; Lin, Honghuan; Jing, Feng; Xu, Dangpeng; Huang, Zhihua; Deng, Ying; Geng, Yuanchao; Li, Mingzhong; Zhang, Rui; Zhu, Na; Wang, Jianjun

2011-04-01

77

Selective amplitude-frequency electro-optical modulation by polymer-dispersed liquid crystal films aligned by teflon nanolayers  

International Nuclear Information System (INIS)

We report the amplitude-frequency electro-optical (EO) modulation by a specific type of polymer-dispersed liquid crystal (PDLC) composites – planar single layers of large nematic microdroplets aligned by teflon nanolayers. Such a surface modifying PDLC system exhibits a selective modulated 2nd harmonic EO response by the dielectric oscillations of the nematic director. The band-like behavioural characteristic of the amplitude-frequency modulation of light, achieved by the single-layered PDLC films, can be tuned by AC voltage applied on the PDLC cell. This property can be applied to tunable EO modulators operating in the infrasound frequency range

78

RF Amplitude Modulation to Suppress Longitudinal Coupled Bunch Instabilities in the SPS  

CERN Document Server

Without specific counter measures, the LHC type beam in the SPS suffers from longitudinal coupled bunch instabilities. To get rid of them, the SPS impedance has been decreased in the last years and the operation of a high frequency Landau damping system has been established. In case of the absence of this Landau damping system one may alternatively introduce an RF amplitude modulation to stabilize the beam. We present results obtained by this method in the SPS and considerations for a potential increase of the longitudinal stability of the LHC.

Vogel, E; Wehrle, U

2004-01-01

79

Broadband nanodielectric spectroscopy by means of amplitude modulation electrostatic force microscopy (AM-EFM)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work we present a new AFM based approach to measure the local dielectric response of polymer films at the nanoscale by means of Amplitude Modulation Electrostatic Force Microscopy (AM-EFM). The proposed experimental method is based on the measurement of the tip-sample force via the detection of the second harmonic component of the photosensor signal by means of a lock-in amplifier. This approach allows reaching unprecedented broad frequency range (2-3×104 Hz) without restrictions on ...

Schwartz, Gustavo Ariel; Riedel, Cle?ment; Arinero, Richard; Tordjeman, Philippe; Alegri?a, Angel; Colmenero, Juan

2011-01-01

80

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

International Nuclear Information System (INIS)

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

 
 
 
 
81

Changes in Auditory Nerve Responses Across the Duration of Sinusoidally Amplitude-Modulated Electric Pulse-Train Stimuli  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Response rates of auditory nerve fibers (ANFs) to electric pulse trains change over time, reflecting substantial spike-rate adaptation that depends on stimulus parameters. We hypothesize that adaptation affects the representation of amplitude-modulated pulse trains used by cochlear prostheses to transmit speech information to the auditory system. We recorded cat ANF responses to sinusoidally amplitude-modulated (SAM) trains with 5,000 pulse/s carriers. Stimuli delivered by a monopolar intraco...

Hu, Ning; Miller, Charles A.; Abbas, Paul J.; Robinson, Barbara K.; Woo, Jihwan

2010-01-01

82

Rayleigh noise mitigation in DWDM LR-PONs using carrier suppressed subcarrier-amplitude modulated phase shift keying.  

Science.gov (United States)

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

Chow, C W; Talli, G; Ellis, A D; Townsend, P D

2008-02-01

83

Measurement of the orbit fluctuation caused by an insertion device with the amplitude modulation method  

International Nuclear Information System (INIS)

We have developed a new method to extract only the orbit fluctuation caused by changing magnetic field error of an insertion device (ID). This method consists of two main parts. (i) The orbit fluctuation is measured with modulating the error field of the ID by using the real-time beam position measuring system. (ii) The orbit fluctuation depending on the variation of the error field of the ID is extracted by the filter applying the Wavelet Transform. We call this approach the amplitude modulation method. This analysis technique was applied to measure the orbit fluctuation caused by the error field of APPLE-2 type undulator (ID23) installed in the SPring-8 storage ring. We quantitatively measured two kinds of the orbit fluctuation which are the static term caused by the magnetic field error and the dynamic term caused by the eddy current on the ID23 chamber

84

Research on signal processing techniques for a chirped amplitude modulation imaging laser radar  

Science.gov (United States)

Due to some significant advantages such as high space resolution, three-dimensional imagery (including intensity image and range image) acquiring, and so on, an imaging laser radar is helpful to improve the correct recognition ratio being as a sensor in a target recognition system. A chirped amplitude modulation imaging ladar is based on the frequency modulation/continuous wave (FM/cw) technique. The target range is calculated by measuring the frequency difference between projected and returned laser signal. The design of a signal processing system for a FM/cw imaging ladar is introduced in this paper, which includes an acquiring block, a memory block, a communication block, and a FFT processor. The performance of this system is analyzed in detail in this paper.

Wang, Yang; Wang, Qianqian; Wang, Haiwei

2010-11-01

85

Terahertz generation by an amplitude-modulated Gaussian laser beam in a rippled density plasma column  

International Nuclear Information System (INIS)

The nonlinear interaction of amplitude-modulated two-dimensional and three-dimensional laser beams with a cylindrical plasma column and the generation of terahertz (THz) radiation are studied. The plasma column could be formed by a cylindrically symmetric laser pre-pulse impinging on a gas jet target. A two-dimensional Gaussian laser beam propagating through the plasma exerts a ponderomotive force on electrons, imparting on them a resonant transverse velocity at the modulation frequency, ?, when ?=?p/?2, where ?p is the plasma frequency of the column. The current produces THz radiation. In the case of a cylindrically symmetric Gaussian laser beam, the electron response to ponderomotive force misses the resonance, yet the phase matching introduced by a density ripple could efficiently produce THz radiation. The power conversion efficiency of the order of the ratio of THz radiation frequency to laser frequency can be achieved at a laser intensity of ?1015 W cm-2 at 1 ?m wavelength.

86

Electromagnetically induced transparency induced by a 100% amplitude-modulated coupling field  

Science.gov (United States)

We present a study of electromagnetically induced transparency (EIT) under the excitation of a 100% amplitude-modulated (AM) coupling field. The EIT feature is associated with a ? type three-level configuration where a coupling and probe field couples two separate optical transitions and it is well-known that the spectrum of the swept probe field gives a simple single transparency feature induced by the single mode coupling field. It is shown that when a 100% AM coupling field is applied, there is an EIT doublet and the separation of the EIT doublet can be controlled by the modulation frequency of the coupling field. Our result implies a new way of manipulating EIT resonance and opening more than one EIT windows.

Li, Xiao-Li; Zhang, Lian-Shui; Yang, Li-Jun; Feng, Xiao-Min; Zhao, Min

2009-01-01

87

Age-related differences in auditory processing as assessed by amplitude-modulation following responses in quiet and in noise  

Directory of Open Access Journals (Sweden)

Full Text Available Our knowledge of age related changes in auditory processing in the central auditory system is limited, unlike the changes in the peripheral hearing organs which are more extensively studied. This study aims to further understanding of temporal processing in aging using non-invasive electrophysiological measurements in a rat model system. Amplitude modulation following responses (AMFRs were assessed using sinusoidally amplitude modulated (SAM tones presented to aged (92-95 weeks old and young (9-12 weeks old Fischer-344 rats. The modulation frequency and sound level were systematically varied, and the SAM stimuli were also presented simultaneously with wide-band background noise at various levels. The overall shapes and cutoff frequencies of the AMFR temporal modulation transfer functions (tMTFs were similar between young and aged animals. The fast Fourier transform (FFT amplitudes of the aged animals were similar to the young in the 181Hz-512Hz modulation frequency range, but were significantly lower at most modulation frequencies above and below. There were no significant age related differences in the nature of growth or FFT amplitudes with change in sound level at 256Hz and 1024Hz modulation frequencies. The AMFR amplitudes were also not correlated with the ABR wave I or wave III amplitudes elicited for broadband click stimuli presented at the same sound level suggesting that sustained AMFR responses provide complementary information to phasic ABR responses. The FFT amplitudes varied significantly between young and aged animals for SAM stimuli in the presence of background noise, depending on the modulation frequency used and signal to noise ratio. The results show that the representation of temporally modulated stimuli is similar between young and aged animals in quiet listening conditions, but diverges substantially with the addition of background noise. This is consistent with a decrease in inhibition causing altered temporal processing with age.

AravindakshanParthasarathy

2010-12-01

88

Regime of a wideband phase-amplitude modulation in a CW magnetron transmitter with a phase control  

CERN Document Server

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...

Kazakevich, G; Chase, B; Pasquinelli, R; Yakovlev, V

2014-01-01

89

Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links  

DEFF Research Database (Denmark)

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.

Iglesias Olmedo, Miguel; Zuo, Tianjian

2014-01-01

90

Influence of stimulus intensity on the soleus H-reflex amplitude and modulation during locomotion  

DEFF Research Database (Denmark)

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.

Simonsen, Erik B; Alkjær, Tine

2013-01-01

91

Effects of weak amplitude-modulated microwave fields on calcium efflux from awake cat cerebral cortex  

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

92

The effect of amplitude modulation on subharmonic imaging with chirp excitation.  

Science.gov (United States)

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

Harput, Sevan; Arif, Muhammad; McLaughlan, James; Cowell, David M J; Freear, Steven

2013-12-01

93

A role for amplitude modulation phase relationships in speech rhythm perception.  

Science.gov (United States)

Prosodic rhythm in speech [the alternation of "Strong" (S) and "weak" (w) syllables] is cued, among others, by slow rates of amplitude modulation (AM) within the speech envelope. However, it is unclear exactly which envelope modulation rates and statistics are the most important for the rhythm percept. Here, the hypothesis that the phase relationship between "Stress" rate (?2?Hz) and "Syllable" rate (?4?Hz) AMs provides a perceptual cue for speech rhythm is tested. In a rhythm judgment task, adult listeners identified AM tone-vocoded nursery rhyme sentences that carried either trochaic (S-w) or iambic patterning (w-S). Manipulation of listeners' rhythm perception was attempted by parametrically phase-shifting the Stress AM and Syllable AM in the vocoder. It was expected that a 1? radian phase-shift (half a cycle) would reverse the perceived rhythm pattern (i.e., trochaic ? iambic) whereas a 2? radian shift (full cycle) would retain the perceived rhythm pattern (i.e., trochaic ? trochaic). The results confirmed these predictions. Listeners judgments of rhythm systematically followed Stress-Syllable AM phase-shifts, but were unaffected by phase-shifts between the Syllable AM and the Sub-beat AM (?14?Hz) in a control condition. It is concluded that the Stress-Syllable AM phase relationship is an envelope-based modulation statistic that supports speech rhythm perception. PMID:24993221

Leong, Victoria; Stone, Michael A; Turner, Richard E; Goswami, Usha

2014-07-01

94

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

Science.gov (United States)

In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer. PMID:24206915

Zimmerman, Jacquelyn W.; Jimenez, Hugo; Pennison, Michael J.; Brezovich, Ivan; Morgan, Desiree; Mudry, Albert; Costa, Frederico P.; Barbault, Alexandre; Pasche, Boris

2013-01-01

95

Terminal residue hydrophobicity modulates transmembrane helix-helix interactions.  

Science.gov (United States)

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

Ng, Derek P; Deber, Charles M

2014-06-17

96

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

Directory of Open Access Journals (Sweden)

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

AravindakshanParthasarathy

2012-11-01

97

Magnetic excitations in the longitudinally amplitude modulated magnetic structure of PrNi2Si2  

International Nuclear Information System (INIS)

Interest in PrNi2Si2 has been renewed recently because the magnetic structure remains longitudinally amplitude modulated down to low temperatures as inferred from single–crystal neutron diffraction. Based on a dynamical matrix diagonalisation (DMD) formalism considering exchange and crystal field interactions, we have calculated the dispersion of the magnetic excitations of PrNi2Si2 below the Néel temperature. The prediction of a low-energy soft-mode excitations around the scattering vector (0,0, Qz) within the first Brillouin zone, where Qz ? kz = 0.875 is the value of the propagation vector of the magnetic structure, is in good agreement with the experimental results obtained from inelastic neutron scattering.

98

Detection performance improvement of chirped amplitude modulation ladar based on Gieger-mode avalanche photoelectric detector.  

Science.gov (United States)

This paper presents an improved system structure of photon-counting chirped amplitude modulation (AM) ladar based on the Geiger-mode avalanche photoelectric detector (GmAPD). The error-pulse probability is investigated with statistical method. The research shows that most of the error pulses that are triggered by noise are distributed in the intensity troughs of the chirped AM waveform. The error-pulse probability is lowered with the sliding window and the threshold. With the average intensity of noise and signal being 0.3 count/sample and 1 count/sample, respectively, the probability of error pulses is reduced from 12% to 1.0%, and the SNR is improved by 2.2 dB in the improved system. PMID:22193131

Zhang, Zijing; Wu, Long; Zhang, Yu; Zhao, Yuan; Sun, Xiudong

2011-12-10

99

Multiple input multiple output underwater communication based on differential amplitude phase shift keying modulation.  

Science.gov (United States)

The MIMO-OFDM combining time, spatial, and frequency diversity can effectively improve channel capacity and transmission efficiency of underwater acoustic (UWA) communication system. Space-time coding needs a large number of pilot signals to estimate UWA channel at the receiving end, which increases the complexity of the systems and limits the communication rate. For this, space-time coding combined with differential amplitude phase shift keying modulation (DAPSK) is proposed in this paper. It can complete the decoding without any prior knowledge of UWA channel, reducing the complexity of the system, saving channel resources and improving the transmission efficiency. Simulation analysis on UWA MIMO-OFDM systems shows this algorithm is feasible, which provides a feasible method for high-speed transmission in UWA communication. PMID:25236149

Xia, Xu; Yin, Jingwei

2014-04-01

100

Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications  

Directory of Open Access Journals (Sweden)

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.

Sethakaset Ubolthip

2005-01-01

 
 
 
 
101

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

Science.gov (United States)

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.

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

2014-08-01

102

Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications  

Directory of Open Access Journals (Sweden)

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.

Sethakaset Ubolthip

2005-01-01

103

Perception of suprathreshold amplitude modulation and intensity increments: Weber's law revisited.  

Science.gov (United States)

The perceived strength of intensity fluctuations evoked by suprathreshold sinusoidal amplitude modulation (AM) and the perceived size of intensity increments were compared across levels of a wideband noise and a 1-kHz tone. For the 1-kHz tone, the comparisons were made in quiet and in a high-pass noise. The data indicate that suprathreshold modulation depths and intensity increments, perceived as equivalent across levels, follow a pattern resembling Weber's law for noise and the "near miss" to Weber's law for a tone. The effect of a high-pass noise was largely consistent with that observed for AM and increment detection. The data suggest that Weber's law is not a direct consequence of the dependence of internal noise on stimulus level, as suggested by multiplicative internal noise models. Equal loudness ratios and equal loudness differences (computed using loudness for the stationary portions before and after the increment) accounted for the increment-matching data for noise and for the tone, respectively, but neither measure predicted the results for both types of stimuli. Predictions based on log-transformed excitation patterns and predictions using an equal number of intensity just-noticeable differences were in qualitative, but not quantitative, agreement with the data. PMID:18397028

Wojtczak, Magdalena; Viemeister, Neal F

2008-04-01

104

Perception of suprathreshold amplitude modulation and intensity increments: Weber's law revisited1  

Science.gov (United States)

The perceived strength of intensity fluctuations evoked by suprathreshold sinusoidal amplitude modulation (AM) and the perceived size of intensity increments were compared across levels of a wideband noise and a 1-kHz tone. For the 1-kHz tone, the comparisons were made in quiet and in a high-pass noise. The data indicate that suprathreshold modulation depths and intensity increments, perceived as equivalent across levels, follow a pattern resembling Weber’s law for noise and the “near miss” to Weber’s law for a tone. The effect of a high-pass noise was largely consistent with that observed for AM and increment detection. The data suggest that Weber’s law is not a direct consequence of the dependence of internal noise on stimulus level, as suggested by multiplicative internal noise models. Equal loudness ratios and equal loudness differences (computed using loudness for the stationary portions before and after the increment) accounted for the increment-matching data for noise and for the tone, respectively, but neither measure predicted the results for both types of stimuli. Predictions based on log-transformed excitation patterns and predictions using an equal number of intensity just-noticeable differences were in qualitative, but not quantitative, agreement with the data. PMID:18397028

Wojtczak, Magdalena; Viemeister, Neal F.

2008-01-01

105

Underwater three-dimensional imaging with an amplitude-modulated laser radar at a 405 nm wavelength.  

Science.gov (United States)

We report the results of underwater imaging with an amplitude-modulated single-mode laser beam and miniaturized piezoactuator-based scanning system. The basic elements of the device are a diode laser source at 405 nm with digital amplitude modulation and a microscanning system realized with a small-aperture aspheric lens mounted on a pair of piezoelectric translators driven by sawtooth waveforms. The system has been designed to be a low-weight and rugged imaging device suitable to operate at medium range (approximately 10 m) in clear seawater as also demonstrated by computer simulation of layout performance. In the controlled laboratory conditions a submillimeter range accuracy has been obtained at a laser amplitude modulation frequency of 36.7 MHz. PMID:16318184

Bartolini, Luciano; De Dominicis, Luigi; de Collibus, Mario Ferri; Fornetti, Giorgio; Guarneri, Massimiliano; Paglia, Emiliano; Poggi, Claudio; Ricci, Roberto

2005-11-20

106

Comparison of discrete multi-tone and pulse amplitude modulation for beyond 100 Gbps short-reach application  

Science.gov (United States)

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.

Nishihara, Masato; Kai, Yutaka; Tanaka, Toshiki; Takahara, Tomoo; Li, Lei; Yan, Weizhen; Liu, Bo; Tao, Zhenning; Rasmussen, Jens C.

2013-12-01

107

Investigation of Multilevel Phase and Amplitude Modulation Formats in Combination With Polarization Multiplexing up to 240 Gb/s  

DEFF Research Database (Denmark)

We present experimental investigations of the receiver sensitivity and dispersion tolerance of multilevel optical communication systems with a symbol rate of 40 Gbaud. Four- and eight-level communication is obtained by combining binary amplitude modulation with either binary or quadrature differential phase modulation. We experimentally compare the dispersion tolerance, and show that multilevel modulation formats offer much better dispersion tolerance compared to binary formats. By combining multilevel modulation with polarization multiplexing, bit rates up to 240 Gb/s were obtained. We demonstrate transmission over 50-km fiber span with no power penalty for a pseudorandom binary sequence length of 27-1 bits.

Tokle, Torger; Jensen, Jesper Bevensee

2006-01-01

108

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

Directory of Open Access Journals (Sweden)

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

Ramadan Ali

2010-01-01

109

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

110

Spin amplitude modulation driven magnetoelectric coupling in the new multiferroic FeTe2O5Br.  

Science.gov (United States)

The magnetic and ferroelectric properties of the layered geometrically frustrated cluster compound FeTe2O5Br were investigated with single-crystal neutron diffraction and dielectric measurements. An incommensurate transverse amplitude modulated magnetic order with the wave vector q=(1/2,0.463,0) develops below T(N)=10.6(2) K. Simultaneously, a ferroelectric order due to exchange striction involving polarizable Te4+ lone-pair electrons develops perpendicular to q and to Fe3+ magnetic moments. The observed magnetoelectric coupling is proposed to originate from the temperature dependent phase difference between neighboring amplitude modulation waves. PMID:19905598

Pregelj, M; Zaharko, O; Zorko, A; Kutnjak, Z; Jeglic, P; Brown, P J; Jagodic, M; Jaglici?, Z; Berger, H; Arcon, D

2009-10-01

111

A robust and dither-free technique for controlling driver signal amplitude for stable and arbitrary optical phase modulation.  

Science.gov (United States)

We propose a robust and dither-free technique using a delay line interferometer, a balanced detector and simple signal processing to adjust the amplitude of the driver signal of an optical phase modulator automatically for stabilizing the modulated phase of an optical carrier at any arbitrary value. The technique is analytically shown to be robust against practical device imperfections. A stable 45 degrees phase shift with deviation less than ± 0.8 degrees is experimentally demonstrated. PMID:22274219

Yang, Yanfu; Lu, Chao; Lau, Alan Pak Tao; Yao, Yong; Sun, Yunxu; Xiao, Jun Jun; Tam, H Y; Wai, P K A

2011-12-19

112

Correlation of neural responses in the cochlear nucleus with low-frequency noise amplitude modulation of a tonal signal  

Science.gov (United States)

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.

Bibikov, N. G.

2014-09-01

113

Forward masking in the amplitude-modulation domain for tone carriers: psychophysical results and physiological correlates.  

Science.gov (United States)

Wojtczak and Viemeister (J Acoust Soc Am 118:3198-3210, 2005) demonstrated forward masking in the amplitude-modulation (AM) domain. The present study examined whether this effect has correlates in physiological responses to AM at the level of the auditory midbrain. The human psychophysical experiment used 40-Hz, 100% AM (masker AM) that was imposed on a 5.5-kHz carrier during the first 150 ms of its duration. The masker AM was followed by a 50-ms burst of AM of the same rate (signal AM) imposed on the same (uninterrupted) carrier, either immediately after the masker or with a delay. In the physiological experiment, single-unit extracellular recordings in the awake rabbit inferior colliculus (IC) were obtained for stimuli designed to be similar to the uninterrupted-carrier conditions used in the psychophysics. The masker AM was longer (500 ms compared with 150 ms in the psychophysical experiment), and the carrier and modulation rate were chosen based on each neuron's audio- and envelope-frequency selectivity. Based on the average discharge rates of the responses or on the temporal correlation between neural responses to masked and unmasked stimuli, only a small subset of the population of IC cells exhibited suppression of signal AM following the masker. In contrast, changes in the discharge rates between the temporal segments of the carrier immediately preceding the signal AM and during the signal AM varied as a function of masker-signal delay with a trend that matched the psychophysical results. Unless the physiological observations were caused by species differences, they suggest that stages of processing higher than the IC must be considered to account for the AM-processing time constants measured perceptually in humans. PMID:21181225

Wojtczak, Magdalena; Nelson, Paul C; Viemeister, Neal F; Carney, Laurel H

2011-06-01

114

Carrierless amplitude phase modulation of VCSEL with 4 bit/s/Hz spectral efficiency for use in WDM-PON  

DEFF Research Database (Denmark)

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.

Rodes Lopez, Roberto; Pham, Tien Thang

2011-01-01

115

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

DEFF Research Database (Denmark)

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 Lopez, Roberto; Pham, Tien Thang

2011-01-01

116

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

Science.gov (United States)

Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms. PMID:24096892

Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

2013-10-30

117

Enabling practical surface acoustic wave nebulizer drug delivery via amplitude modulation.  

Science.gov (United States)

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

Rajapaksa, Anushi; Qi, Aisha; Yeo, Leslie Y; Coppel, Ross; Friend, James R

2014-06-01

118

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

Science.gov (United States)

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

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

2013-01-01

119

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

Science.gov (United States)

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

Herlory, Olivier; Bonzom, Jean-Marc; Gilbin, Rodolphe

2013-09-15

120

FIBER OPTICS. ACOUSTOOPTICS: Amplitude and phase nonreciprocities of acoustooptic modulators for counterpropagating light waves under the Bragg diffraction conditions  

Science.gov (United States)

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.

Veselovskaya, T. V.; Klochan, E. L.; Lariontsev, E. G.; Parfenov, S. V.; Shelaev, A. N.

1990-07-01

 
 
 
 
121

A new tracking error detection method using amplitude difference detection for signal waveform modulation multi-level discs  

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)

122

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

International Nuclear Information System (INIS)

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

123

Time-resolved study of amplitude modulation effects in surface-wave atmospheric pressure argon plasma jet  

Science.gov (United States)

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.

Hnilica, J.; Kudrle, V.

2014-02-01

124

Ponderomotively-Generated Magnetic Field in a Relativistic Gaussian Amplitude Modulated Laser Filament in an Inhomogeneous Plasma  

Science.gov (United States)

A relativistic short laser pulse is modeled having amplitude modulation in time and Gaussian profile of intensity distribution transverse to the direction of laser propagation. The relativistic laser exerts a ponderomotive force on the electrons imparting them an oscillatory velocity. When the plasma has a density gradient perpendicular to this ponderomotive force, a quasistatic magnetic field is produced. The magnetic field lasts for duration of the laser pulse. At plasma resonance (?p approx ?/2), the magnetic field is enhanced significantly.

Kumar, Asheel

2005-01-01

125

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

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

126

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-09-15

127

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

DEFF Research Database (Denmark)

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.

Peucheret, Christophe; Lorenzen, Michael Rodas

2008-01-01

128

The effect of carrier level on tuning in amplitude-modulation masking.  

Science.gov (United States)

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 rather than improved modulation-frequency selectivity. Consistent with this interpretation, the addition of a high-pass noise with a level adjusted to maintain the same threshold for the detection of the signal modulation for each carrier level used eliminated the effect of level on tuning. Overall, modulation filters estimated from psychophysical data do not depend on level in contrast to the modulation transfer functions obtained from neural recordings in the inferior colliculus in physiological studies. The results highlight differences between the characteristics of modulation processing obtained from neural data and perception. The discrepancies indicate the need for further investigation into physiological correlates of tuning in modulation processing. PMID:22225047

Wojtczak, Magdalena

2011-12-01

129

The effect of carrier level on tuning in amplitude-modulation maskinga  

Science.gov (United States)

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 rather than improved modulation-frequency selectivity. Consistent with this interpretation, the addition of a high-pass noise with a level adjusted to maintain the same threshold for the detection of the signal modulation for each carrier level used eliminated the effect of level on tuning. Overall, modulation filters estimated from psychophysical data do not depend on level in contrast to the modulation transfer functions obtained from neural recordings in the inferior colliculus in physiological studies. The results highlight differences between the characteristics of modulation processing obtained from neural data and perception. The discrepancies indicate the need for further investigation into physiological correlates of tuning in modulation processing. PMID:22225047

Wojtczak, Magdalena

2011-01-01

130

Experimental evidence of signal-optical noise interferencelike effect in underwater amplitude-modulated laser optical radar systems.  

Science.gov (United States)

We report experimental evidence that in an amplitude-modulated laser optical radar system for underwater 3D imaging the observed contrast oscillations as a function of the modulation frequency originate from an interference-like effect between target signal VT and water backscattered radiation VW. The demonstration relies on the ability to perform a direct measurement of VW in a 25 m long test tank. The proposed data processing method enables one to remove the contribution of water backscattering from the detected signal and drastically reduce signal fluctuations due to the medium. Experiments also confirm the possibility to improve the signal to optical noise ratio and contrast by increasing the modulation frequency. PMID:19015675

Bartolini, L; De Dominicis, L; Ferri de Collibus, M; Fornetti, G; Francucci, M; Guarneri, M; Nuvoli, M; Paglia, E; Ricci, R

2008-11-15

131

Triggerable electro-optic amplitude modulator bias stabilizer for integrated optical devices  

Science.gov (United States)

An improved Mach-Zehnder integrated optical electro-optic modulator is achieved by application and incorporation of a DC bias box containing a laser synchronized trigger circuit, a DC ramp and hold circuit, a modulator transfer function negative peak detector circuit, and an adjustable delay circuit. The DC bias box ramps the DC bias along the transfer function curve to any desired phase or point of operation at which point the RF modulation takes place.

Conder, Alan D. (Tracy, CA); Haigh, Ronald E. (Tracy, CA); Hugenberg, Keith F. (Livermore, CA)

1995-01-01

132

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

Science.gov (United States)

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

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

2011-07-01

133

Practical use of the amplitude and phase modulation of a high-power RF pulse via feed-forward control  

International Nuclear Information System (INIS)

A new feed-forward control system to precisely control the amplitude and phase of the pulsed RF power in an electron linear accelerator (linac) is developed to make the accelerating field constant. Fast variations and ripples in the amplitude and phase in the RF pulses are compensated by modulating the amplitude and phase in the low-level system with a variable attenuator and phase shifter. The system is innovated the overdrive technique, which is commonly used in analog circuits, to speed up the slow response of the phase shifter, while the control signals are digitally processed; thus, the method is a hybrid of analog and digital techniques. By using the new control system, we find that the peak-to-peak variations in the amplitude and phase are reduced from 11.6% to 0.4% and from 6.1 degrees to 0.3 degrees, respectively, in 7.6-?s-long RF pulses for the L-band electron linac at Osaka University. (author)

134

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

Directory of Open Access Journals (Sweden)

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

Hassan Farhan Rashag

2013-04-01

135

Spectral phase, amplitude, and spatial modulation from ultraviolet to infrared with a reflective MEMS pulse shaper  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We describe the performance of a reflective pulse-shaper based on a Micro-ElectroMechanical System (MEMS) linear mirror array. It represents a substantial upgrade of a preceding release [Opt. Lett. 35, 3102 (2010)] as it allows simultaneous piston and tilt mirror motion, allowing both phase- and binary amplitude-shaping with no wavelength restriction. Moreover, we show how the combination of in-axis and tilt movement can be used for active correction of spatial chirp.

Extermann, Je?ro?me; Weber, Stefan; Kiselev, Denis; Bonacina, Luigi; Lani, Se?bastien; Jutzi, Fabio; Noell, Wilfried; Rooij, Nico F.; Wolf, Jean-pierre

2011-01-01

136

Spectral phase, amplitude, and spatial modulation from ultraviolet to infrared with a reflective MEMS pulse shaper.  

Science.gov (United States)

We describe the performance of a reflective pulse-shaper based on a Micro-ElectroMechanical System (MEMS) linear mirror array. It represents a substantial upgrade of a preceding release [Opt. Lett. 35, 3102 (2010)] as it allows simultaneous piston and tilt mirror motion, allowing both phase- and binary amplitude-shaping with no wavelength restriction. Moreover, we show how the combination of in-axis and tilt movement can be used for active correction of spatial chirp. PMID:21503066

Extermann, Jérôme; Weber, Stefan M; Kiselev, Denis; Bonacina, Luigi; Lani, Sébastien; Jutzi, Fabio; Noell, Wilfried; de Rooij, Nico F; Wolf, Jean-Pierre

2011-04-11

137

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Nigam, R.; Kosovichev, A. G.

2009-01-01

138

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

DEFF Research Database (Denmark)

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.

Mosekilde, Erik

2011-01-01

139

Operational modes of a ferroelectric LCoS modulator for displaying binary polarization, amplitude, and phase diffraction gratings.  

Science.gov (United States)

We analyze the performance of a ferroelectric liquid crystal on silicon display (FLCoS) as a binary polarization diffraction grating. We analyze the correspondence between the two polarization states emerging from the displayed grating and the polarization and intensity of the diffracted orders generated at the Fourier diffraction plane. This polarization-diffraction analysis leads, in a simple manner, to configurations yielding binary amplitude or binary phase modulation by incorporating an analyzer on the reflected beam. Based on this analysis, we present two useful variations of the polarization configuration. The first is a simplification using a single polarizer, which provides equivalent results for amplitude or phase modulation as the more general operational mode involving two polarizers. The second variation is proposed to compensate the reduction of the diffraction efficiency when the operating wavelength differs from the design one (for which the FLCoS liquid-crystal layer acts as a half-wave plate). In this situation we show how the ideal grating performance can be recovered in spite of the phase-shift mismatch originated by chromatic dispersion. In all cases, we provide experimental results that verify the theoretical analyses. PMID:19458742

Martínez-García, Antonio; Moreno, Ignacio; Sánchez-López, María M; García-Martínez, Pascuala

2009-05-20

140

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

Directory of Open Access Journals (Sweden)

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.

Korman Maria

2011-12-01

 
 
 
 
141

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

DEFF Research Database (Denmark)

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.

Teodorescu, Kinneret; Bouchigny, Sylvain

2011-01-01

142

Correlation between residual stress and plastic strain amplitude during low cycle fatigue of mechanically surface treated austenitic stainless steel AISI 304 and ferritic-pearlitic steel SAE 1045  

Energy Technology Data Exchange (ETDEWEB)

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.

Nikitin, I. [Institute of Materials Engineering, University of Kassel, 34125 Kassel, Hessen (Germany)], E-mail: Ivan.Nikitin@infineon.com; Besel, M. [Institute of Materials Engineering, University of Kassel, 34125 Kassel, Hessen (Germany)

2008-09-15

143

Correlation between residual stress and plastic strain amplitude during low cycle fatigue of mechanically surface treated austenitic stainless steel AISI 304 and ferritic-pearlitic steel SAE 1045  

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

144

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

Science.gov (United States)

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

Kumar, Bharat; Bonvallet, Joseph; Crittenden, Scott

2012-02-01

145

Practical method to limit tip-sample contact stress and prevent wear in amplitude modulation atomic force microscopy.  

Science.gov (United States)

Amplitude modulation atomic force microscopy (AM-AFM) is one of the most popular AFM modes because of the reduced tip-sample interaction, compared to contact mode AFM, and the ability to acquire high-resolution images while interrogating the sample's material composition through phase imaging. Despite the reduced tip-sample interaction, tip and sample wear can occur through gradual atomic scale processes that can significantly accumulate due to the high frequency of the tip-sample interaction and through high intermittent contact stresses. Starting from existing analytical formulations, we introduce a method for selecting an appropriate probe and free oscillation amplitude that avoids exceeding a critical contact stress to minimize tip/sample damage. The approach is presented for the case of both a Hertzian- and a Derjaguin-Müller-Toporov-like tip-sample contact. Stress maps and related simplified formulas are provided that enable one to determine allowable free oscillation amplitudes to stay below a target contact stress for given cantilever and sample parameters (combined into a single "cantilever-sample constant" that we introduce). Experimental results show how sharp silicon tips, either uncoated or coated with diamond-like carbon and silicon nitride, interacting with a hard and wear-resistant sample (ultrananocrystalline diamond) can be preserved while attaining high-quality AM-AFM images by using our proposed scheme. We also show that using our analysis to select parameters that exceed the target contact stress indeed leads to significant tip wear. This method provides AM-AFM users with a better understanding of contact stresses and enables selection of AM-AFM cantilevers and experimental parameters that preserve the tip for long periods of use and prevents the sample from damage. PMID:24131354

Vahdat, Vahid; Carpick, Robert W

2013-11-26

146

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

Science.gov (United States)

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

Epping, W J; Eggermont, J J

1986-01-01

147

The effects of adsorbed water layers on the apparent height of nanostructures in ambient amplitude modulation atomic force microscopy  

Science.gov (United States)

Ambient amplitude modulation atomic force microscopy (AM AFM) is one of the most broadly used techniques as it is versatile and can provide measurements of single nanostructures routinely. Nevertheless, the technique typically measures an apparent height of nanostructures that does not coincide with the true height. Here, we carry out an exhaustive study of the several possibilities that arise in the presence and in the absence of adsorbed water layers when measuring the height of nanostructures. A method to control whether water layers are perturbed and whether intermittent mechanical contact occurs is provided. We show that the predicted range of apparent heights in the several interaction regimes is as large as the experimental values that are routinely obtained. In one extreme the apparent height might be larger than the true height even when sample deformation occurs. In the other, height reversal might occur even when sample deformation is much smaller than the loss of height. A main mechanism leading to such a broad range of measurements is identified in terms of the presence of water layers and the long range character of the resulting forces. In short, due to these long range effects, the gap in separation in the two amplitude branches, i.e., the attractive and the repulsive regimes, might be an order of magnitude larger in the presence of water than in its absence.

Santos, Sergio; Verdaguer, Albert; Chiesa, Matteo

2012-07-01

148

Multiple transmitter performance with appropriate amplitude modulation for free-space optical communication.  

Science.gov (United States)

The propagation of a free-space optical communications signal through atmospheric turbulence experiences random fluctuations in intensity, including signal fades, which negatively impact the performance of the communications link. The gamma-gamma probability density function is commonly used to model the scintillation of a single beam. One proposed method to reduce the occurrence of scintillation-induced fades at the receiver plane involves the use of multiple beams propagating through independent paths, resulting in a sum of independent gamma-gamma random variables. Recently an analytical model for the probability distribution of irradiance from the sum of multiple independent beams was developed. Because truly independent beams are practically impossible to create, we present here a more general but approximate model for the distribution of beams traveling through partially correlated paths. This model compares favorably with wave-optics simulations and highlights the reduced scintillation as the number of transmitted beams is increased. Additionally, a pulse-position modulation scheme is used to reduce the impact of signal fades when they occur. Analytical and simulated results showed significantly improved performance when compared to fixed threshold on/off keying. PMID:21857696

Tellez, Jason A; Schmidt, Jason D

2011-08-20

149

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

Scientific Electronic Library Online (English)

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

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

150

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

CERN Document Server

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

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

2013-01-01

151

Despeckle Filtering for Multiscale Amplitude-Modulation Frequency-Modulation (AM-FM) Texture Analysis of Ultrasound Images of the Intima-Media Complex.  

Science.gov (United States)

The intima-media thickness (IMT) of the common carotid artery (CCA) is widely used as an early indicator of cardiovascular disease (CVD). Typically, the IMT grows with age and this is used as a sign of increased risk of CVD. Beyond thickness, there is also clinical interest in identifying how the composition and texture of the intima-media complex (IMC) changed and how these textural changes grow into atherosclerotic plaques that can cause stroke. Clearly though texture analysis of ultrasound images can be greatly affected by speckle noise, our goal here is to develop effective despeckle noise methods that can recover image texture associated with increased rates of atherosclerosis disease. In this study, we perform a comparative evaluation of several despeckle filtering methods, on 100 ultrasound images of the CCA, based on the extracted multiscale Amplitude-Modulation Frequency-Modulation (AM-FM) texture features and visual image quality assessment by two clinical experts. Texture features were extracted from the automatically segmented IMC for three different age groups. The despeckle filters hybrid median and the homogeneous mask area filter showed the best performance by improving the class separation between the three age groups and also yielded significantly improved image quality. PMID:24734038

Loizou, C P; Murray, V; Pattichis, M S; Pantziaris, M; Nicolaides, A N; Pattichis, C S

2014-01-01

152

Rapid transport of nano-particles in amplitude modulated rf discharges for depositing porous ultra-low-k films  

Science.gov (United States)

We have proposed a novel one-step method for synthesizing nano-particle composite porous low-k films. For the method, nano-particles as nano-building blocks and radicals as adhesives are produced in reactive discharge plasmas; both of them are transported to a substrate; and eventually nano-particles are co-deposited there together with radicals. Size of nano-particles is controlled by the duration of pulse rf discharge; their rapid transport of a velocity more than 60 cm/s is realized by pulse rf discharges with an amplitude modulation (AM) of the discharge voltage. The deposition rate with AM is 0.65 nm/s, which is 7 times as high as that without AM, while dielectric constant k = 1.1-1.4 and porosity = 60-63% of the films with AM are nearly equal to those without AM. Therefore deposition of porous low-k films using pulse rf discharges with AM is a promising method for increasing the deposition rate without varying the properties of films.

Iwashita, S.; Morita, M.; Koga, K.; Shiratani, M.

2008-03-01

153

Rapid transport of nano-particles in amplitude modulated rf discharges for depositing porous ultra-low-k films  

International Nuclear Information System (INIS)

We have proposed a novel one-step method for synthesizing nano-particle composite porous low-k films. For the method, nano-particles as nano-building blocks and radicals as adhesives are produced in reactive discharge plasmas; both of them are transported to a substrate; and eventually nano-particles are co-deposited there together with radicals. Size of nano-particles is controlled by the duration of pulse rf discharge; their rapid transport of a velocity more than 60 cm/s is realized by pulse rf discharges with an amplitude modulation (AM) of the discharge voltage. The deposition rate with AM is 0.65 nm/s, which is 7 times as high as that without AM, while dielectric constant k = 1.1-1.4 and porosity = 60-63% of the films with AM are nearly equal to those without AM. Therefore deposition of porous low-k films using pulse rf discharges with AM is a promising method for increasing the deposition rate without varying the properties of films

154

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

Science.gov (United States)

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

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

2014-08-22

155

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

Directory of Open Access Journals (Sweden)

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.

P. A. Janakiraman

2010-01-01

156

Sleep restriction attenuates amplitudes and attentional modulation of pain-related evoked potentials, but augments pain ratings in healthy volunteers.  

Science.gov (United States)

The experiment investigated the impact of sleep restriction on pain perception and related evoked potential correlates (laser-evoked potentials, LEPs). Ten healthy subjects with good sleep quality were investigated in the morning twice, once after habitual sleep and once after partial sleep restriction. Additionally, we studied the impact of attentional focussing on pain and LEPs by directing attention to (intensity discrimination) or away from the stimulus (mental arithmetic). Laser stimuli directed to the hand dorsum were rated as 30% more painful after sleep restriction (49+/-7 mm) than after a night of habitual sleep (38+/-7 mm). A significant interaction between attentional focus and sleep condition suggested that attentional focusing was less distinctive under sleep restriction. Intensity discrimination was preserved. In contrast, the amplitude of the early parasylvian N1 of LEPs was significantly smaller after a night of partial sleep restriction (-36%, ppartial sleep restriction. We propose, that sleep reduction leads to an impairment of activation in the ascending pathway (leading to reduced LEPs). In contradistinction, pain perception was boosted, which we attribute to lack of pain control distinct from classical descending inhibition, and thus not affecting the projection pathway. Sleep-restricted subjects exhibit reduced attentional modulation of pain stimuli and may thus have difficulties to readily attend to or disengage from pain. PMID:19864066

Tiede, Wiebke; Magerl, Walter; Baumgärtner, Ulf; Durrer, Benno; Ehlert, Ulrike; Treede, Rolf-Detlef

2010-01-01

157

Explanation and correction of false step heights in amplitude modulation atomic force microscopy measurements on alkane films  

International Nuclear Information System (INIS)

We use a prototypical alkane film (n-C32H66 or C32) adsorbed on a SiO2 surface to compare step heights measured by amplitude modulation atomic force microscopy (AM-AFM) with those measured in the contact mode. The C32 film exhibits layers in which the molecules are oriented with their long axis parallel to the SiO2 surface followed by partial layers of perpendicular molecules. We show that step heights measured in the AM and contact modes agree in all cases except where the step is between a surface formed by a layer of parallel molecules and one of perpendicular molecules. In this case, the AM mode gives a false step height that is as much as 20% lower than that measured in the contact mode and inferred from synchrotron X-ray specular reflectivity measurements. We propose that the weaker van der Waals forces between the AFM tip and a perpendicular layer compared to a parallel layer causes this discrepancy. We show how to correct the false step height by using the approximately linear relationship observed between phase angle (cantilever oscillation relative to the drive signal) and cantilever height measured in an approach curve

158

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

International Nuclear Information System (INIS)

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

159

Factorization of Mellin amplitudes  

CERN Document Server

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.

Gonçalves, Vasco; Trevisani, Emilio

2014-01-01

160

Experimental demonstration of 10 Gb/s multi-level carrier-less amplitude and phase modulation for short range optical communication systems.  

Science.gov (United States)

Carrier-less amplitude and phase (CAP) modulation can be a good candidate for short range optical communications for considerable computational complexity reduction and simple system structure. In this paper, a detailed investigation on the digital filters in CAP modulation system is presented. An adaptive equalizer based on cascaded multi-modulus algorithm (CMMA) is used for the demodulation at the receiver. The impact of digital filter taps on system performance is investigated through comprehensive simulations and a 10 Gb/s CAP16 modulation system is demonstrated experimentally. The BER performance for different length of fiber link is measured. Compared with back-to-back (BTB) transmissions, 2 dB and 3.5 dB receiver power penalty are observed at BER of 10(-3) for 20 km and 40 km fiber link respectively. It clearly demonstrates the feasibility of the CAP16 modulation for the short range transmission systems. PMID:23482215

Tao, Li; Wang, Yiguang; Gao, Yuliang; Lau, Alan Pak Tao; Chi, Nan; Lu, Chao

2013-03-11

 
 
 
 
161

Gatekeeper residues in the major curlin subunit modulate bacterial amyloid fiber biogenesis.  

Science.gov (United States)

Amyloid fibers are filamentous protein structures commonly associated with neurodegenerative diseases. Unlike disease-associated amyloids, which are the products of protein misfolding, Escherichia coli assemble membrane-anchored functional amyloid fibers called curli. Curli fibers are composed of two proteins, CsgA and CsgB. In vivo, the polymerization of the major curli subunit protein, CsgA, is dependent on CsgB-mediated nucleation. The amyloid core of CsgA features five imperfect repeats (R1-R5), and R1 and R5 govern CsgA responsiveness to CsgB nucleation and self-seeding by CsgA fibers. Here, the specificity of bacterial amyloid nucleation was probed, revealing that certain aspartic acid and glycine residues inhibit the intrinsic aggregation propensities and nucleation responsiveness of R2, R3, and R4. These residues function as "gatekeepers" to modulate CsgA polymerization efficiency and potential toxicity. A CsgA molecule lacking gatekeeper residues polymerized in vitro significantly faster than wild-type CsgA and polymerized in vivo in the absence of the nucleation machinery, resulting in mislocalized fibers. This uncontrolled polymerization was associated with cytotoxicity, suggesting that incorrectly regulated CsgA polymerization was detrimental to the cell. PMID:19966296

Wang, Xuan; Zhou, Yizhou; Ren, Juan-Jie; Hammer, Neal D; Chapman, Matthew R

2010-01-01

162

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

Science.gov (United States)

Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6 m telescope, under programme LP185.D-0056. Based on observations obtained with the HERMES spectrograph attached to the 1.2 m Mercator telescope, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientific (FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland, and the Thüringer Landessternwarte Tautenburg, Germany. Based on observations obtained with the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU).

Aerts, C.; Simón-Díaz, S.; Catala, C.; Neiner, C.; Briquet, M.; Castro, N.; Schmid, V. S.; Scardia, M.; Rainer, M.; Poretti, E.; Pápics, P. I.; Degroote, P.; Bloemen, S.; Østensen, R. H.; Auvergne, M.; Baglin, A.; Baudin, F.; Michel, E.; Samadi, R.

2013-09-01

163

Dependence of Modulation Amplitude on Electron Density in Unidirectional Lateral Superlattices: The Effect of the Thickness of the Two-dimensional Electron Gas  

CERN Document Server

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| roughly an order of magnitude larger for the former method. The result is interpreted in terms of the rate, dE_1/d(delta E_c), of the change in the first subband level E_1 in response to the variation of the conduction-band edge delta E_c above the heterointerface. The rate crucially depends on the thickness of the 2DEG.

Endo, A; Endo, Akira; Iye, Yasuhiro

2005-01-01

164

High-Speed Phase-Modulation Atomic Force Microscopy in Constant-Amplitude Mode Capable of Simultaneous Measurement of Topography and Energy Dissipation  

Science.gov (United States)

We have developed high-speed phase-modulation atomic force microscopy (PM-AFM) in a constant-amplitude (CA) mode. Using this imaging mode, we have theoretically demonstrated that energy dissipation due to tip-sample interaction can be obtained from the excitation amplitude of a cantilever. Moreover, we have found that the photothermal excitation method is better than the acoustic excitation method for cantilever oscillation in liquids. For the first time, we have demonstrated that a homebuilt high-speed PM-AFM in the CA mode has the capability to simultaneously measure the topography and energy dissipation with a material-specific contrast for a PS/PIB polymer-blend film.

Li, Yan Jun; Kobayashi, Naritaka; Nomura, Hikaru; Naitoh, Yoshitaka; Kageshima, Masami; Sugawara, Yasuhiro

2008-07-01

165

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

CERN Document Server

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

Thanassoulas, C; Verveniotis, G

2010-01-01

166

Polarimetry as a valid means to reduce optical noise in underwater 3D imaging by means of amplitude-modulated laser optical radar systems.  

Science.gov (United States)

We report the results of a series of underwater imaging experiments in the visible, carried out at ENEA (Frascati, Rome) by using a bistatic, amplitude-modulated laser optical radar system. In these experiments, polarimetry is used for minimizing the water backscattering signal and improving the accuracy of phase measurements directly related to distance. The presented technique enables one to obtain 3D images of underwater real scenes characterized by high quality, space resolution, and contrast. The results are of remarkable importance for applications in the 3D imaging of submerged objects, such as submarine archaeological sites. PMID:19823520

De Dominicis, L; Ferri de Collibus, M; Fornetti, G; Francucci, M; Guarneri, M; Nuvoli, M; Paglia, E; Ricci, R

2009-07-15

167

Calcium Input Frequency, Duration and Amplitude Differentially Modulate the Relative Activation of Calcineurin and CaMKII  

Digital Repository Infrastructure Vision for European Research (DRIVER)

NMDA receptor dependent long-term potentiation (LTP) and long-term depression (LTD) are two prominent forms of synaptic plasticity, both of which are triggered by post-synaptic calcium elevation. To understand how calcium selectively stimulates two opposing processes, we developed a detailed computational model and performed simulations with different calcium input frequencies, amplitudes, and durations. We show that with a total amount of calcium ions kept constant, high frequencies of calci...

Li, Lu; Stefan, Melanie I.; Le Nove?re, Nicolas

2012-01-01

168

A comparison of single-sideband, suppressed-carrier and double-sideband, full-carrier amplitude modulation  

Science.gov (United States)

The spectral economy of SSB (single-sideband, suppressed-carrier modulation) in comparison with conventional AM has long been recognized. However, the use of SSB, particularly for data transmission, has been limited by the large peak envelope excursions caused by pulse-like waveforms. Even in the transmission of analog signals, such as speech or music, undesirable peaks can be encountered. SSB and AM signals are analyzed using a waveform that can be varied in shape from a spike through a sine wave to a square wave by varying a parameter. The average sideband powers and the peak envelope powers are then calculated and compared. It is shown that the ratio of average sideband power to peak envelope power for AM is more favorable than that for SSB for squarish modulating signals. However, the ratio for SSB is about 9dB higher than it is for AM for modulating signals ranging in shape from a sine wave to a spike.

Bedrosian, Edward; Sollfrey, William

1986-08-01

169

Design and Construction of a Simple but Efficient and Cost Effective Amplitude Modulated Transmitter Using Locally Available Materials  

Directory of Open Access Journals (Sweden)

Full Text Available This work is an exploration of the design foundation and construction of an AM Transmitter. An AM transmitter controls the transmitting and broadcasting of signals that supports information conveyance in the AM Bandwidth. A brief introduction of the concept of AM transmission is followed by detailed discussion of design and construction. The discussion is organized under the 5 stages of the AM transmitter unit, namely; Power supply, Audio Amplification, carrier wave oscillation, modulation, and the RF Power Amplification Stages.

Aru Okereke Eze

2014-02-01

170

Evolution of Residual Stress and Structure in YSZ/SiO2 Multilayers with Different Modulation Ratios  

Science.gov (United States)

The multilayer (ML) YSZ/SiO2 films with different modulation ratios ranging from 1:3, 4:9, 1:1 to 3:1 (the thickness ratio of the YSZ to SiO2) are deposited on BK7 glass substrates by electron beam evaporation under the same processing conditions. The effect of modulation ratio on the residual stresses and structure are investigated by an optical interferometer and Grazing incidence x-ray diffraction. The results show that the total residual stress in MLs is compressive and decreases to tensile when the modulation ratio is changed from 1:3 to 3:1. The YSZ films are of cubic phase structure and the SiO2 films are amorphous in all the MLs. The change of residual stress in these MLs can be attributed to the variation of an individual layer?s stress with thickness, which indicates that adjusting the thickness ratio of two materials is an effective measure for depositing near-zero stress MLs.

Xiao, Qi-Ling; Hu, Guo-Hang; He, Hong-Bo; Shao, Jian-Da

2013-02-01

171

Evolution of Residual Stress and Structure in YSZ/SiO2 Multilayers with Different Modulation Ratios  

International Nuclear Information System (INIS)

The multilayer (ML) YSZ/SiO2 films with different modulation ratios ranging from 1:3, 4:9, 1:1 to 3:1 (the thickness ratio of the YSZ to SiO2) are deposited on BK7 glass substrates by electron beam evaporation under the same processing conditions. The effect of modulation ratio on the residual stresses and structure are investigated by an optical interferometer and Grazing incidence x-ray diffraction. The results show that the total residual stress in MLs is compressive and decreases to tensile when the modulation ratio is changed from 1:3 to 3:1. The YSZ films are of cubic phase structure and the SiO2 films are amorphous in all the MLs. The change of residual stress in these MLs can be attributed to the variation of an individual layer?s stress with thickness, which indicates that adjusting the thickness ratio of two materials is an effective measure for depositing near-zero stress MLs

172

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

CERN Document Server

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.

Zhang, Jie-Fang; Meng, Jianping; Wu, Lei; Malomed, Boris A

2010-01-01

173

Distributed auditory cortical representations are modified when non-musicians are trained at pitch discrimination with 40 Hz amplitude modulated tones.  

Science.gov (United States)

Several functional brain attributes reflecting neocortical activity have been found to be enhanced in musicians compared to non-musicians. Included are the N1m evoked magnetic field, P2 and right-hemispheric N1c auditory evoked potentials, and the source waveform of the magnetically recorded 40 Hz auditory steady state response (SSR). We investigated whether these functional brain attributes measured by EEG are sensitive to neuroplastic remodeling in non-musician subjects. Adult non-musicians were trained for 15 sessions to discriminate small changes in the carrier frequency of 40 Hz amplitude modulated pure tones. P2 and N1c auditory evoked potentials were separated from the SSR by signal processing and found to localize to spatially differentiable sources in the secondary auditory cortex (A2). Training enhanced the P2 bilaterally and the N1c in the right hemisphere where auditory neurons may be specialized for processing of spectral information. The SSR localized to sources in the region of Heschl's gyrus in primary auditory cortex (A1). The amplitude of the SSR (assessed by bivariate T2 in 100 ms moving windows) was not augmented by training although the phase of the response was modified for the trained stimuli. The P2 and N1c enhancements observed here and reported previously in musicians may reflect new tunings on A2 neurons whose establishment and expression are gated by input converging from other regions of the brain. The SSR localizing to A1 was more resistant to remodeling, suggesting that its amplitude enhancement in musicians may be an intrinsic marker for musical skill or an early experience effect. PMID:15115745

Bosnyak, Daniel J; Eaton, Robert A; Roberts, Larry E

2004-10-01

174

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

Directory of Open Access Journals (Sweden)

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

A. K. Sinha

175

Dynamic responses of Ar-CO2 and Ar-N2 induction thermal plasmas in pulse amplitude modulation approach  

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

176

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Studies of the structure-function relationship in proteins for which no 3D structure is available are often based on inspection of multiple sequence alignments. Many functionally important residues of proteins can be identified because they are conserved during evolution. However, residues that vary can also be critically important if their variation is responsible for diversity of protein function and improved phenotypes. If too few sequences are studied,...

Li Bin; Gallin Warren J

2005-01-01

177

The production of vasoconstriction-induced residual NO modulates perfusion pressure in rat mesenteric vascular bed.  

Science.gov (United States)

In the presence of nitric oxide synthase (NOS) inhibitors, the contribution of residual NO to endothelium-dependent relaxation induced by chemical agonists acetylcholine and bradykinin has been documented in resistance vessels. However, the contribution of residual NO to the vasodilatation in response to pressure and fluid shear stress is not well understood. In this study, to demonstrate the activity of residual NO, we applied a NO scavenger, hydroxocobalamin (HCX), on the phenylephrine-induced increase in perfusion pressure in the presence of NOS inhibitors, N?-nitro-L-arginine (L-NA) or N?-nitro-L-arginine methyl ester (L-NAME) in the rat perfused mesenteric bed. The perfusion pressure was increased by phenylephrine (1-2 µM), an ?1-adrenoceptor agonist. This increase was augmented by the addition of L-NA or L-NAME. In the presence of any NOS inhibitors, the application of hydroxocobalamin (100 µM) further increased the perfusion pressure. The removal of endothelium by saponin (50 mg/L) and the use of a non-selective protein kinase inhibitor, staurosporine (5 nM), and a tyrosine kinase inhibitor, erbstatin A (30 µM), but not a calmodulin inhibitor, calmidazolium (0.5 µM), inhibited the additional pressor responses induced by L-NA or L-NAME and a combination of either of them with hydroxocobalamine. These findings show that there could be a NOS inhibitor-resistant residual NO production in response to pressure in the rat mesenteric vascular bed. This residual NO production may be associated with the activation of tyrosine kinase and protein kinases, but not calmodulin. Finally, this pressure-induced residual NO exerts a modulatory role against vasoconstriction induced by phenylephrine. PMID:24534887

Seçilmi?, Ma; Ozü, Oy; K?ro?lu, Oe; Singirik, E; Büyükaf?ar, K

2014-11-01

178

Residual third-order dispersion compensation in femtosecond pulses transmission using a phase modulator  

Science.gov (United States)

Using the split-step Fourier method, the nonlinear effects and higher-order dispersion in optical fiber are studied and numerically analyzed. Based on the analysis, the theoretical model of higher-order dispersion compensation with phased modulator is presented, with emphasis on the third-order dispersion. According to the theoretical model, simulation models based on VPItransmission is designed. Finally, experimental schemes are designed, and experiment is finished: 200-fs pulses propagate through a 47-km fiber link, including a 39.8-km SMF (single-mode fiber) and a 6.71-km DCF (dispersion-compensation fiber). In that experiment, the oscillating tails are completely suppressed and the third-order dispersion is successfully compensated with the phase modulator. Moreover, the parameters of modulator are optimized with VPItransmission Modeling.

Zhang, Rui; Yang, Xiaozhou; Cai, Yue; Hu, Weiwei; Zhang, Zhigang

2008-11-01

179

Nonconserved active site residues modulate CheY autophosphorylation kinetics and phosphodonor preference.  

Science.gov (United States)

In two-component signal transduction, response regulator proteins contain the catalytic machinery for their own covalent phosphorylation and can catalyze phosphotransfer from a partner sensor kinase or autophosphorylate using various small molecule phosphodonors. Although response regulator autophosphorylation is physiologically relevant and a powerful experimental tool, the kinetic determinants of the autophosphorylation reaction and how those determinants might vary for different response regulators and phosphodonors are largely unknown. We characterized the autophosphorylation kinetics of 21 variants of the model response regulator Escherichia coli CheY that contained substitutions primarily at nonconserved active site positions D + 2 (CheY residue 59) and T + 2 (CheY residue 89), two residues C-terminal to conserved D57 and T87, respectively. Overall, the CheY variants exhibited a >10(5)-fold range of rate constants (kphos/KS) for reaction with phosphoramidate, acetyl phosphate, or monophosphoimidazole, with the great majority of rates enhanced versus that of wild-type CheY. Although phosphodonor preference varied substantially, nearly all the CheY variants reacted faster with phosphoramidate than acetyl phosphate. Correlation between the increased positive charge of the D + 2 and T + 2 side chains and faster rates indicated electrostatic interactions are a kinetic determinant. Moreover, sensitivities of rate constants to ionic strength indicated that both long-range and localized electrostatic interactions influence autophosphorylation kinetics. The increased nonpolar surface area of the D + 2 and T + 2 side chains also correlated with an enhanced autophosphorylation rate, especially for reaction with phosphoramidate and monophosphoimidazole. Computer docking suggested that highly accelerated monophosphoimidazole autophosphorylation rates for CheY variants with a tyrosine at position T + 2 likely reflect structural mimicry of phosphotransfer from the sensor kinase histidyl phosphate. PMID:23458124

Thomas, Stephanie A; Immormino, Robert M; Bourret, Robert B; Silversmith, Ruth E

2013-04-01

180

Temperature effects on Microalgal Photosynthesis-Light responses measured by O2 production, Pulse-Amplitude-Modulated Fluorescence, and 14C assimilation  

DEFF Research Database (Denmark)

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.

Hancke, Kasper; Hancke, Torunn

2008-01-01

 
 
 
 
181

A conformationally mobile cysteine residue (Cys-561) modulates Na+ and H+ activation of human CNT3.  

Science.gov (United States)

In humans, the SLC28 concentrative nucleoside transporter (CNT) protein family is represented by three Na+-coupled members; human CNT1 (hCNT1) and hCNT2 are pyrimidine and purine nucleoside-selective, respectively, whereas hCNT3 transports both purine and pyrimidine nucleosides and nucleoside drugs. Belonging to a phylogenetic CNT subfamily distinct from hCNT1/2, hCNT3 also mediates H+/nucleoside cotransport. Using heterologous expression in Xenopus oocytes, we have characterized a cysteineless version of hCNT3 (hCNT3C-). Processed normally to the cell surface, hCNT3C- exhibited hCNT3-like transport properties, but displayed a decrease in apparent affinity specific for Na+ and not H+. Site-directed mutagenesis experiments in wild-type and hCNT3C- backgrounds identified intramembranous Cys-561 as the residue responsible for this altered Na+-binding phenotype. Alanine at this position restored Na+ binding affinity, whereas substitution with larger neutral amino acids (threonine, valine, and isoleucine) abolished hCNT3 H+-dependent nucleoside transport activity. Independent of these findings, we have established that Cys-561 is located in a mobile region of the hCNT3 translocation pore adjacent to the nucleoside binding pocket and that access of p-chloromercuribenzene sulfonate to this residue reports a specific H+-induced conformational state of the protein ( Slugoski, M. D., Ng, A. M. L., Yao, S. Y. M., Smith, K. M., Lin, C. C., Zhang, J., Karpinski, E., Cass, C. E., Baldwin, S. A., and Young, J. D. (2008) J. Biol. Chem. 283, 8496-8507 ). The present investigation validates hCNT3C- as a template for substituted cysteine accessibility method studies of CNTs and reveals a pivotal functional role for Cys-561 in Na+- as well as H+-coupled modes of hCNT3 nucleoside transport. PMID:18621735

Slugoski, Melissa D; Smith, Kyla M; Mulinta, Ras; Ng, Amy M L; Yao, Sylvia Y M; Morrison, Ellen L; Lee, Queenie O T; Zhang, Jing; Karpinski, Edward; Cass, Carol E; Baldwin, Stephen A; Young, James D

2008-09-01

182

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

Science.gov (United States)

To determine whether residual interfraction seminal vesicle (SV) displacement necessitates specific planning target volume (PTV) margins during fiducial-guided intensity modulated radiation therapy (IMRT) of the prostate. A planning computed tomography (CT) scan and 2 subsequent CT scans were prospectively obtained for 20 prostate cancer patients with intraprostatic fiducial markers. After CT registration, SV displacement relative to the prostate was quantified as a function of margin size for both the proximal (1 cm) SV (PSV) and the full SV (FSV). Two IMRT plans were simulated for each patient (prostate + PSV and prostate + FSV) both with a uniform 5-mm PTV margin. Minimum clinical target volume (CTV) dose (D(min)) and the volume of SV receiving 95% of the prescription dose (V(95%)) were assessed during treatment and compared with the initial plan. In all cases, SV displacement with respect to the prostate was greater for the FSV compared with the PSV. To ensure at least 95% geometrical coverage of the CTV for 90% of patients, margins of 5 and 8 mm were required for the PSV and FSV, respectively. Dosimetrically, residual SV displacement had minimal impact on PSV coverage compared with FSV coverage. For the PSV D(min) was ?95% of the prescribed dose in 90% of patients with an overall mean V(95%) of 99.6 ± 0.8%; for the FSV D(min) was ?95% of the prescribed dose in only 45% of patients with a mean V(95%) of 97.9 ± 2.4%. The SVs move differentially from the prostate and exhibit greater variation with increasing distance from the prostate. For plans targeting just the prostate and PSVs, 5-mm PTV expansions are adequate. However, despite daily localization of the prostate, larger PTV margins are required for cases where the intent is to completely cover the FSV. PMID:22189029

Stenmark, Matthew H; Vineberg, Karen; Ten Haken, Randall K; Hamstra, Daniel A; Feng, Mary

2012-01-01

183

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

International Nuclear Information System (INIS)

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

184

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

CERN Document Server

"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.

Hanzo, Lajos

2004-01-01

185

Mutational Insights into the Roles of Amino Acid Residues in Ligand Binding for Two Closely Related Family 16 Carbohydrate Binding Modules  

Energy Technology Data Exchange (ETDEWEB)

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.

Su, Xiaoyun; Agarwal, Vinayak; Dodd, Dylan; Bae, Brian; Mackie, Roderick I.; Nair, Satish K.; Cann, Isaac K.O. (UIUC)

2010-11-22

186

Modulation of Cholesterol and Copper Residue Levels in Muscles and Blood Serum of Finishing Broiler Chickens Fed Copper and Ascorbic Acid Supplements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To study the effect of Copper (Cu) and ascorbic acid supplements on modulation of cholesterol and copper residue content of chicken muscles and blood serum, two hundred and forty finishing Anak broiler chickens of mixed sexes were randomly allotted to four dietary treatment groups with four replication of fifteen birds each. The feeding period was 5 weeks. The response to copper and ascorbic acid were such that dietary supplementation with 250 ppm Cu alone resulted in 30 and 19% reduction in ...

Oso, A. O.; Fafiolu, A. O.; Ajuwon, O. R.; Idowu, O. M. O.; Akinloye, O. A.

2011-01-01

187

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)

188

Mutation of conserved negatively charged residues in the S2 and S3 transmembrane segments of a mammalian K+ channel selectively modulates channel gating.  

Science.gov (United States)

Voltage-gated channel proteins sense a change in the transmembrane electric field and respond with a conformational change that allows ions to diffuse across the pore-forming structure. Site-specific mutagenesis combined with electrophysiological analysis of expressed mutants in amphibian oocytes has previously established the S4 transmembrane segment as an element of the voltage sensor. Here, we show that mutations of conserved negatively charged residues in S2 and S3 of a brain K+ channel, thought of as countercharges for the positively charged residues in S4, selectively modulate channel gating without modifying the permeation properties. Mutations of Glu235 in S2 that neutralize or reverse charge increase the probability of channel opening and the apparent gating valence. In contrast, replacements of Glu272 by Arg or Thr268 by Asp in S3 decrease the open probability and the apparent gating valence. Residue Glu225 in S2 tolerated replacement only by acidic residues, whereas Asp258 in S3 was intolerant to any attempted change. These results imply that S2 and S3 are unlikely to be involved in channel lining, yet, together with S4, may be additional components of the voltage-sensing structure. PMID:7568145

Planells-Cases, R; Ferrer-Montiel, A V; Patten, C D; Montal, M

1995-01-01

189

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1969-07-01

190

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

CERN Document Server

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...

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

2013-01-01

191

11 × 5 × 9.3Gb/s WDM-CAP-PON based on optical single-side band multi-level multi-band carrier-less amplitude and phase modulation with direct detection.  

Science.gov (United States)

We propose and demonstrate a novel WDM-CAP-PON based on optical single-side band (OSSB) multi-level multi-band carrier-less amplitude and phase modulation (MM-CAP). To enable high-speed transmission with simplified optical network unit (ONU)-side digital signal processing, 4-level 5 sub-bands CAP-16 is used here, which is generated by the digital to analogue converter (DAC). Optical single-side band (OSSB) technology is applied to extend the transmission distance against the spectrum fading effect. As a proof of concept, the experiment successfully demonstrates 11 WDM channels, 55 sub-bands, for 55 users with 9.3-Gb/s per user (after removing 7% overhead for forward error correction (FEC)) in the downstream over 40-km SMF. PMID:23938798

Zhang, Junwen; Yu, Jianjun; Li, Fan; Chi, Nan; Dong, Ze; Li, Xinying

2013-08-12

192

Scattering Amplitudes in Gauge Theories  

CERN Document Server

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...

Schubert, Ulrich

2014-01-01

193

Experimental study on MOSFET pulse modulator  

International Nuclear Information System (INIS)

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

194

Modulation of Cholesterol and Copper Residue Levels in Muscles and Blood Serum of Finishing Broiler Chickens Fed Copper and Ascorbic Acid Supplements  

Directory of Open Access Journals (Sweden)

Full Text Available To study the effect of Copper (Cu and ascorbic acid supplements on modulation of cholesterol and copper residue content of chicken muscles and blood serum, two hundred and forty finishing Anak broiler chickens of mixed sexes were randomly allotted to four dietary treatment groups with four replication of fifteen birds each. The feeding period was 5 weeks. The response to copper and ascorbic acid were such that dietary supplementation with 250 ppm Cu alone resulted in 30 and 19% reduction in pectoralis major and biceps femoris muscles cholesterol respectively. Supplementation with 250 ppm Cu + 100 ppm Ascorbic acid resulted in 29 and 12% reduction in muscles cholesterol while inclusion of 100 ppm ascorbic acid alone brought about 4 and 10% reduction in the two muscles respectively. Serum cholesterol reduced by 28% and the addition 100 ppm ascorbic acid reduced this to 26%. Ascorbic acid (100 ppm exerted 12% reduction in serum cholesterol. Ascorbic lowered the hypocholesterolemic potency of copper by about 1-7%. Combination of 100 ppm ascorbic and 250 ppm Cu slowed down rate of weight gain by 11% when compared with 250 ppm Cu alone as supplement, Supplementation with 100 ppm ascorbic alone improved carcass yield by 4% compared to 250 ppm Cu. Metalloprotein enzyme (AST and ALP activities were significantly increased with supplementation. Cu residue was more in biceps femoris than pectoralis major muscle. Above 30% reduction in Cu residue was noticed with addition of ascorbic acid.

A.O. Oso

2011-01-01

195

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-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

196

Algebras for Amplitudes  

CERN Document Server

Tree-level amplitudes of gauge theories are expressed in a basis of auxiliary amplitudes with only cubic vertices. The vertices in this formalism are explicitly factorized in color and kinematics, clarifying the color-kinematics duality in gauge theory amplitudes. The basis is constructed making use of the KK and BCJ relations, thereby showing precisely how these relations underlie the color-kinematics duality. We express gravity amplitudes in terms of a related basis of color-dressed gauge theory amplitudes, with basis coefficients which are permutation symmetric.

Bjerrum-Bohr, N E J; Monteiro, Ricardo; O'Connell, Donal

2012-01-01

197

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

Science.gov (United States)

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

Cockburn, Darrell W; Clarke, Anthony J

2011-05-01

198

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

DEFF Research Database (Denmark)

One industrial process for the production of cellulosic ethanol and or value-added products involves exposing the cellulose content of plant materials by steam explosion in the presence of strong acid, followed by its neutralization and subsequent digestion with a cocktail of cellulolytic enzymes. These enzymes typically have activity optima at slightly acidic or neutral pH and so generating enzymes that are more active and tolerant in more acidic conditions would help to reduce associated costs. Here, we describe the engineering of cellulase A from Cellulomonas fimi as a model to replace residues that were identified as potentially influencing the pH-activity profile of the enzyme based on sequence alignments and analysis of the known three-dimensional structures of other CAZy family 6 glycoside hydrolases with the aim to lower its pH optimum. Twelve specific residues and a sequence of eight were identified and a total of 30 mutant enzymes were generated. In addition to being replaced with natural amino acids, some of the identified residues were substituted with cysteine and subsequently oxidized to cysteinesulfinate. Of the four single amino acid replacements that produced enhancements of activity at acidic pH, three involved the removal of charged groups from the surface of the enzyme. The generation of double mutations provided mixed results but the combination of Glu407?Ala and Tyr321?Phe replacements had an additive effect on the enhancement, reaching a total activity that was 162 of the wild-type level. This study thus illustrated the utility of altering the surface charge properties of the family 6 glycoside hydrolases to enhance activity at low pH and thereby an avenue for further protein engineering. © 2011 The Author Published by Oxford University Press. All rights reserved.

Cockburn, Darrell W.; Clarke, Anthony J.

2011-01-01

199

AQP4 plasma membrane trafficking or channel gating is not significantly modulated by phosphorylation at C-terminal serine residues  

DEFF Research Database (Denmark)

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.

Assentoft, Mette; Larsen, Brian R

2014-01-01

200

Modulation of substrate preference of thermus maltogenic amylase by mutation of the residues at the interface of a dimer.  

Science.gov (United States)

To elucidate the relationship between the substrate size and geometric shape of the catalytic site of Thermus maltogenic amylase, Gly50, Asp109, and Val431, located at the interface of the dimer, were replaced with bulky amino acids. The k(cat)/K(m) value of the mutant for amylose increased significantly, whereas that for amylopectin decreased as compared to that of the wild-type enzyme. Thus, the substituted bulky amino acid residues modified the shape of the catalytic site, such that the ability of the enzyme to distinguish between small and large molecules like amylose and amylopectin was enhanced. PMID:17587692

Park, Sung-Hoon; Kang, Hee-Kwon; Shim, Jae-Hoon; Woo, Eui-Jeon; Hong, Jung-Sun; Kim, Jung-Wan; Oh, Byung-Ha; Lee, Byong Hoon; Cha, Hyunju; Park, Kwan-Hwa

2007-06-01

 
 
 
 
201

Allosteric modulation of a neuronal K+ channel by 1-alkanols is linked to a key residue in the activation gate.  

Science.gov (United States)

The selective inhibition of neuronal Shaw2 K+ channels by 1-alkanols is conferred by the internal S4-S5 loop, a region that also contributes to the gating of voltage-gated K+ channels. Here, we applied alanine scanning mutagenesis to examine the contribution of the S5 and S6 segments to the allosteric modulation of Shaw2 K+ channels by 1-alkanols. The internal section of S6 is the main activation gate of K+ channels. While several mutations in S5 and S6 modulated the inhibition of the channels by 1-butanol and others had no effect, a single mutation at a key site in S6 (P410A) converted this inhibition into a dramatic dose-dependent potentiation (approximately 2-fold at 15 mM and approximately 6-fold at 50 mM). P410 is the second proline in the highly conserved PVP motif that may cause a significant alpha-helix kink. The P410A currents in the presence of 1-butanol also exhibited novel kinetics (faster activation and slow inactivation). Internal application of 15 mM 1-butanol to inside-out patches expressing P410A did not significantly affect the mean unitary currents (approximately 2 pA at 0 mV) or the mean open time (5-6 ms) but clearly increased the opening frequency and open probability (approximately 2- to 4-fold). All effects displayed a fast onset and were fully reversible upon washout. The results suggest that the allosteric modulation of the Shaw2 K+ channel by 1-alkanols depends on a critical link between the PVP motif and activation gating. This study establishes the Shaw2 K+ channel as a robust model to investigate the mechanisms of alcohol intoxication and general anesthesia. PMID:12958027

Harris, Thanawath; Graber, Andrew R; Covarrubias, Manuel

2003-10-01

202

All-optical phase-preserving multilevel amplitude regeneration.  

Science.gov (United States)

The possibility of all-optical phase-preserving amplitude regeneration for star-8QAM is demonstrated using a modified nonlinear optical loop mirror. Experiments show a reduction in amplitude noise on both amplitude levels simultaneously, considering two different types of signal distortions: deterministic low-frequency amplitude modulation and broadband amplitude noise. Furthermore, using this amplitude regeneration, the robustness against nonlinear phase noise from fiber nonlinearity in a transmission line is increased. The scheme suppresses the conversion of amplitude noise to nonlinear phase noise. This is shown for simultaneous amplitude regeneration of the two amplitude states as well as for amplitude regeneration of the high-power states only. If the transmission is limited by nonlinear phase noise, single-level operation at the more critical higher-power state will benefit because of the wider plateau region. Numerical simulations confirm the experimental results. PMID:25401858

Roethlingshoefer, Tobias; Richter, Thomas; Schubert, Colja; Onishchukov, Georgy; Schmauss, Bernhard; Leuchs, Gerd

2014-11-01

203

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

International Nuclear Information System (INIS)

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

204

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

Science.gov (United States)

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.

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

205

An airborne amplitude-modulated 1.57 ?m differential laser absorption spectrometer: simultaneous measurement of partial column-averaged dry air mixing ratio of CO2 and target range  

Directory of Open Access Journals (Sweden)

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.

O. Uchino

2013-02-01

206

Cepheid radial velocity amplitude modulations (Anderson, 2014)  

Science.gov (United States)

A total of 983 radial velocity measurements of the four Cepheids QZ Nor (125), V335 Pup (95), l Car (324), and RS Pup (439) are provided. The measurements are based on observations carried out between April 2011 and February 2014 that were obtained using the Coralie spectrograph, mounted to the Swiss 1.2m Euler telescope located at La Silla Observatory, Chile. For each Cepheid, a table with the barycentric Julian date of observation, radial velocity, and the measurement uncertainty are provided. In addition, a table containing the identifiers, coordinates, and pulsation periods used to phase-fold the data (see the figures in the article) is provided. (5 data files).

Anderson, R. I.

2014-06-01

207

Calculating scattering amplitudes efficiently  

International Nuclear Information System (INIS)

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

208

Design of a compressed air modulator to be used in comprehensive multidimensional gas chromatography and its application in the determination of pesticide residues in grapes.  

Science.gov (United States)

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 (RSD<18.4%), demonstrating that the performance of the total method consisting of a modified Luke extraction method and determination by GCxGC-microECD are satisfactory. This study also showed that the system using a modulator with a double jet of compressed air 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

Pizzutti, Ionara R; Vreuls, René J J; de Kok, André; Roehrs, Rafael; Martel, Samile; Friggi, Caroline A; Zanella, Renato

2009-04-10

209

Nullification of threshold amplitudes  

International Nuclear Information System (INIS)

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

210

Amplitudes, acquisition and imaging  

Energy Technology Data Exchange (ETDEWEB)

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.

Bloor, Robert

1998-12-31

211

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-04-30

212

Connection between the period and the amplitude of the Blazhko effect  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Benko?, J. M.; Szabo?, R.

2014-01-01

213

Experiment of 2.56-Tb/s, polarization division multiplexing return-to-zero 16-ary quadrature amplitude modulation, 25 GHz grid coherent optical wavelength division multiplexing, 800 km transmission based on optical comb in standard single-mode fiber  

Science.gov (United States)

Based on recirculating frequency shifter, we generate 20 high-quality multicarrier optical combs with a tone-to-noise ratio >25 dB. We also experimentally demonstrate 2.56-Tb/s, polarization division multiplexing return-to-zero 16-ary quadrature amplitude modulation, coherent optical wavelength division multiplexing transmission over 800 km standard single-mode fiber with 25-GHz channel spacing, and the spectrum efficiency is 5.1 b/s/Hz.

Tian, Feng; Zhang, Xiaoguang; Xi, Lixia; Stark, Andy; Ralph, Stephen E.; Chang, Gee-kung

2013-11-01

214

Amplitude interference and interferometry  

International Nuclear Information System (INIS)

The performance of the electron beam interformeter are discussed. When the interferometer is based on the observation of an interference pattern the original incident beam has to be well-collimated and the allowable misalignment is small. This allowable misalignment increasing with the angle spread of the incident electron beams a convergent electron beam can be used. The electron interferometer based on amplitude interferences is more advantageous. The amplitude interference may be accomplished through the Fraunhofer diffraction of two coherent beams by a crystal, a convergent electron beam is also used

215

Impact of residual setup error on parotid gland dose in intensity-modulated radiation therapy with or without planning organ-at-risk margin  

Energy Technology Data Exchange (ETDEWEB)

Purpose: To estimate the dosimetric impact of residual setup errors on parotid sparing in head-and-neck (H and N) intensity-modulated treatments and to evaluate the effect of employing an PRV (planning organ-at-risk volume) margin for the parotid gland. Patients and methods: Ten patients treated for H and N cancer were considered. A nine-beam intensity-modulated radiotherapy (IMRT) was planned for each patient. A second optimization was performed prescribing dose constraint to the PRV of the parotid gland. Systematic setup errors of 2 mm, 3 mm, and 5 mm were simulated. The dose-volume histograms of the shifted and reference plans were compared with regard to mean parotid gland dose (MPD), normal-tissue complication probability (NTCP), and coverage of the clinical target volume (V{sub 95%} and equivalent uniform dose [EUD]); the sensitivity of parotid sparing on setup error was evaluated with a probability-based approach. Results: MPD increased by 3.4%/mm and 3.0%/mm for displacements in the craniocaudal and lateral direction and by 0.7%/mm for displacements in the anterior-posterior direction. The probability to irradiate the parotid with a mean dose > 30 Gy was > 50%, for setup errors in cranial and lateral direction and < 10% in the anterior-posterior direction. The addition of a PRV margin improved parotid sparing, with a relative reduction in NTCP of 14%. The PRV margin compensates for setup errors of 3 mm and 5 mm (MPD {<=} 30 Gy in 87% and 60% of cases), without affecting clinical target volume coverage (V{sub 95%} and EUD variations < 1% and < 1 Gy). Conclusion: The parotid gland is more sensitive to craniocaudal and lateral displacements. A setup error of 2 mm guarantees an MPD {<=} 30 Gy in most cases, without adding a PRV margin. If greater displacements are expected/accepted, an adequate PRV margin could be used to meet the clinical parotid gland constraint of 30 Gy, without affecting target volume coverage. (orig.)

Delana, Anna; Menegotti, Loris; Valentini, Aldo [Dept. of Medical Physics, S. Chiara Hospital, APSS Trento (Italy); Bolner, Andrea; Tomio, Luigi; Vanoni, Valentina [Div. of Radiation Oncology, S. Chiara Hospital, APSS Trento (Italy); Lohr, Frank [Dept. of Radiation Oncology, Univ. Medical Center Mannheim, Univ. of Heidelberg, Mannheim (Germany)

2009-07-15

216

Analysis of amplitude and phase coupling in volume holography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work we analyse the complex amplitude response of volume holograms. This analysis suggests a new scheme for encoding complex amplitude wavefront information onto an optical hologram which may prove useful for combining computer-generated holograms (CGH) onto volume holograms. Specifically, we analyse the amplitude and phase modulation associated with a volume phase unslanted transmission grating. Using the expressions given by the Kogelnik's coupled wave theory (KCWT) we find that the...

Ma?rquez Ruiz, Andre?s; Neipp Lo?pez, Cristian; Yaroslavsky, Leonid P.; Gallego Rico, Sergi; Ortun?o Sa?nchez, Manuel; Bele?ndez Va?zquez, Augusto; Pascual Villalobos, Inmaculada

2005-01-01

217

Reinforcing Saccadic Amplitude Variability  

Science.gov (United States)

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…

Paeye, Celine; Madelain, Laurent

2011-01-01

218

Amplitude and Ascoli analysis  

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.)

219

Measurement of Small One-Bond Proton-Carbon Residual Dipolar Coupling Constants in Partially Oriented 13C Natural Abundance Oligosaccharide Samples: Analysis of Heteronuclear 1JCH-Modulated Spectra with the BIRD Inversion Pulse  

Science.gov (United States)

Two 2D J-modulated HSQC-based experiments were designed for precise determination of small residual dipolar one-bond carbon-proton coupling constants in 13C natural abundance carbohydrates. Crucial to the precision of a few hundredths of Hz achieved by these methods was the use of long modulation intervals and BIRD pulses, which acted as semiselective inversion pulses. The BIRD pulses eliminated effective evolution of all but 1JCH couplings, resulting in signal modulation that can be described by simple modulation functions. A thorough analysis of such modulation functions for a typical four-spin carbohydrate spin system was performed for both experiments. The results showed that the evolution of the 1H- 1H and long-range 1H- 13C couplings during the BIRD pulses did not necessitate the introduction of more complicated modulation functions. The effects of pulse imperfections were also inspected. While weakly coupled spin systems can be analyzed by simple fitting of cross peak intensities, in strongly coupled spin systems the evolution of the density matrix needs to be considered in order to analyse data accurately. However, if strong coupling effects are modest the errors in coupling constants determined by the "weak coupling" analysis are of similar magnitudes in oriented and isotropic samples and are partially cancelled during dipolar coupling calculation. Simple criteria have been established as to when the strong coupling treatment needs to be invoked.

Pham, Tran Nghia; Liptaj, Tibor; Bromek, Krystyna; Uhrín, Dušan

2002-08-01

220

Light Meson Distribution Amplitudes  

CERN Document Server

We calculated the first two moments of the light-cone distribution amplitudes for the pseudoscalar mesons ($\\pi$ and $K$) and the longitudinally polarised vector mesons ($\\rho$, $K^*$ and $\\phi$) as part of the UKQCD and RBC collaborations' $N_f=2+1$ domain-wall fermion phenomenology programme. These quantities were obtained with a good precision and, in particular, the expected effects of $SU(3)$-flavour symmetry breaking were observed. Operators were renormalised non-perturbatively and extrapolations to the physical point were made, guided by leading order chiral perturbation theory. The main results presented are for two volumes, $16^3\\times 32$ and $24^3\\times 64$, with a common lattice spacing. Preliminary results for a lattice with a finer lattice spacing, $32^3\\times64$, are discussed and a first look is taken at the use of twisted boundary conditions to extract distribution amplitudes.

Arthur, R; Brommel, D; Donnellan, M A; Flynn, J M; Juttner, A; de Lima, H Pedroso; Rae, T D; Sachrajda, C T; Samways, B

2010-01-01

 
 
 
 
221

CAMAC amplitude analyzer with improved loading ability  

International Nuclear Information System (INIS)

An amplitude analyzer on the base of the autonomous controller intended for analog and analog-to-digital processing of signals from semiconducting detectors is described. Analog signal processing is carried out by a processor with time-dependent parameters constructed on the base of two CAMAC moduli. The first module represents an amplifier with the gain factor from 2 to 103. The second module is a multifunctional device including controlled reshaper and shaping filter, an inspector of overlappings, an amplitude-time converter as well as the control circuit and the intermodulus exchange of logic signals. Software permits to present data in linear and logarithmic scale, to determine peak duration at the levels of 0.1 and 0.5 as well as the position of their center of gravity and square with deduction of background

222

Universal boundary reflection amplitudes  

CERN Document Server

For all affine Toda field theories we propose a new type of generic boundary bootstrap equations, which can be viewed as a very specific combination of elementary boundary bootstrap equations. These equations allow to construct generic solutions for the boundary reflection amplitudes, which are valid for theories related to all simple Lie algebras, that is simply laced and non-simply laced. We provide a detailed study of these solutions for concrete Lie algebras in various representations.

Castro-Alvaredo, O A; Castro-Alvaredo, Olalla; Fring, Andreas

2003-01-01

223

Constitutive activity modulation of human metabotropic glutamate 5a receptors in HEK293 cells: a role for key amino-terminal cysteine residues  

Science.gov (United States)

Several combinations of cysteine to serine mutations at positions 57, 93, 99 and 129 in the extracellular N-terminal domain of human metabotropic 5a (hmGlu5a) receptors were produced and expressed in HEK293 cells. Quisqualic acid-induced intracellular calcium ([Ca2+]i) mobilization and inositol phosphates (IP) accumulation revealed an apparent increased efficacy and decreased potency for hmGlu5a mutants C57S, C99S and C57/99S, as well as a total loss of function for the mutant C57/93/99/129S. [3H]Quisqualate saturation analysis revealed mutants C57S, C99S, C57/99S and the tetramutant C57/93/99/129S to have unchanged KD but reduced Bmax values. [3H]MPEP saturation analysis on the same membrane preparations revealed no difference in KD for any mutant, but a decrease in Bmax value for the C57/93/99/129S receptor. Inverse agonism of MPEP at hmGlu5a receptors was partially reduced by mutation C57S, significantly reduced by C99S and C57/99S mutations and totally abolished in the tetramutant. We confirmed the surface expression of all the mutated receptors using [3H]MPEP binding analysis on whole cells. However, Bmax values were increased for mutant C57S, C99S, and C57/99S but decreased in the C57/93/99/129S receptor. The 24?h preincubation of cells expressing hmGlu5a receptors with 1??M MPEP followed by extensive washing dramatically increased the wild-type receptor efficacy to quisqualate, to the same levels seen with C57/99S receptors. MPEP preincubation did not affect C57/99S function. We conclude that cysteines 57 and 99 are key residues necessary for modulating hmGlu5a receptor function. PMID:15700023

Muhlemann, Andreas; Diener, Catherine; Fischer, Christophe; Piussi, Jenny; Stucki, Andy; Porter, Richard H

2005-01-01

224

Fusing gauge theory tree amplitudes into loop amplitudes  

CERN Document Server

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

Bern, Z; Dunbar, D C; Kosower, D A; Bern, Z; Dixon, L; Dunbar, D C; Kosower, D A

1994-01-01

225

Fusing gauge theory tree amplitudes into loop amplitudes  

International Nuclear Information System (INIS)

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

226

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2010-09-23

227

Universal boundary reflection amplitudes  

International Nuclear Information System (INIS)

For all affine Toda field theories we propose a new type of generic boundary bootstrap equations, which can be viewed as a very specific combination of elementary boundary bootstrap equations. These equations allow to construct general solutions for the boundary reflection amplitudes, which are valid for theories related to all simple Lie algebras, that is simply laced and non-simply laced. We provide a detailed study of these solutions for concrete Lie algebras in various representations. The boundary bootstrap equations relating different types of exited boundary states are not automatically solved by our expressions

228

Universal boundary reflection amplitudes  

Energy Technology Data Exchange (ETDEWEB)

For all affine Toda field theories we propose a new type of generic boundary bootstrap equations, which can be viewed as a very specific combination of elementary boundary bootstrap equations. These equations allow to construct general solutions for the boundary reflection amplitudes, which are valid for theories related to all simple Lie algebras, that is simply laced and non-simply laced. We provide a detailed study of these solutions for concrete Lie algebras in various representations. The boundary bootstrap equations relating different types of exited boundary states are not automatically solved by our expressions.

Castro-Alvaredo, Olalla; Fring, Andreas E-mail: a.fring@city.ac.uk

2004-03-29

229

Portable pulse modulator  

International Nuclear Information System (INIS)

The 60 kg portable pulse modulator of 800 kW pulse power (pulse amplitude is 18 kV, pulse width-30 ?s, repetition frequency-150 Hz) is described. The specific feature of the modulator - the absence of a power transformer. The conclusion is drawn that the modulator is reliable and efficient in operation

230

Time-amplitude converter  

International Nuclear Information System (INIS)

It is normal in high energy physics to measure the time of flight of a particle in order to determine its mass. This can be done by the method which consists in transforming the time measurement into an analysis of amplitude, which is easier; a time-amplitude converter has therefore been built for this purpose. The apparatus here described uses a double grid control tube 6 BN 6 whose resolution time, as measured with a pulse generator, is 5 x 10-11 s. The analysis of the response of a particle counter, made up of a scintillator and a photomultiplier, indicates that a time of resolution of 5 x 10-10 s. can be obtained. A time of this order of magnitude is obtained experimentally with the converter. This converter has been used in the study of the time of flight of particles in a secondary beam of the accelerator Saturne. It has thus been possible to measure the energy spectrum of ?-mesons, of protons, and of deutons emitted from a polyethylene target bombarded by 1,4 and 2 GeV protons. (author)

231

Fatigue crack growth under variable amplitude loading  

Science.gov (United States)

Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.

Sidawi, Jihad A.

1994-09-01

232

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-04-30

233

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

Science.gov (United States)

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.

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

234

Dual Amplitude-Width PPM for Free Space Optical Systems  

Directory of Open Access Journals (Sweden)

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.

Mehdi Rouissat

2012-04-01

235

Forward masking of frequency modulation.  

Science.gov (United States)

Forward masking of sinusoidal frequency modulation (FM) was measured with three types of maskers: FM, amplitude modulation (AM), and a masker created by combining the magnitude spectrum of an FM tone with random component phases. For the signal FM rates used (5, 20, and 40 Hz), an FM masker raised detection thresholds in terms of frequency deviation by a factor of about 5 relative to without a masker. The AM masker produced a much smaller effect, suggesting that FM-to-AM conversion did not contribute substantially to the FM forward masking. The modulation depth of an FM masker had a nonmonotonic effect, with maximal masking observed at an intermediate value within the range of possible depths, while the random-phase FM masker produced less masking, arguing against a spectrally-based explanation for FM forward masking. Broad FM-rate selectivity for forward masking was observed for both 4-kHz and 500-Hz carriers. Thresholds measured as a function of the masker-signal delay showed slow recovery from FM forward masking, with residual masking for delays up to 500 ms. The FM forward-masking effect resembles that observed for AM [Wojtczak and Viemeister (2005). J. Acoust. Soc. Am. 188, 3198-3210] and may reflect modulation-rate selective neural adaptation to FM. PMID:23145618

Byrne, Andrew J; Wojtczak, Magdalena; Viemeister, Neal F

2012-11-01

236

Renormalization of Massless Feynman Amplitudes in Configuration Space  

CERN Document Server

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.

Nikolov, Nikolay M

2013-01-01

237

Renormalization of massless Feynman amplitudes in configuration space  

Science.gov (United States)

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.

Nikolov, Nikolay M.; Stora, Raymond; Todorov, Ivan

2014-05-01

238

Generator of stable amplitude spectroscopy pulses  

International Nuclear Information System (INIS)

A generator aimed at energy spectrum calibration and testing of electronics is described. The device is performed as a CAMAC 2M module and consists of a current pulses generator and charge sensitive amplifier. Both the self-oscillation regime and primary launched regime are possible. The output frequency can vary from 20 to 200 Hz. The maximal amplitude of single pulse is 5 V for a high-resistance load and 2.5 V for 50 ?. A stable amplitude of spectroscopic pulses (0.01%/oC) is insured. It is possible to use the device as a generator of double pulses, delay can vary from 80 ns to 100 ?s between pulses in the pair in this case. (author)

239

Unitarized pion-nucleon scattering amplitude from inverse amplitude method  

International Nuclear Information System (INIS)

In a recent work on low energy pion-nucleon scattering, instead of using chiral perturbation theory (ChPT) amplitude, we started from a pion-nucleon soft-pion result and used elastic unitarity directly as a dynamical constraint to construct first-order unitarity corrected amplitudes. The resulting amplitudes are crossing symmetric but, as the ChPT ones, satisfy only approximate unitarity relation. In the present work, we reconsider our approach and we apply the inverse amplitude method (IAM) in order to access the energy resonance region. We present the resulting S- and P-wave phase shifts that are shown to be in qualitative agreement with experimental data

240

Large Amplitude Oscillations in Prominences  

CERN Document Server

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...

Tripathi, D; Jain, R

2009-01-01

 
 
 
 
241

Connection between the period and the amplitude of the Blazhko effect  

CERN Document Server

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.

Benk?, J M

2014-01-01

242

Amplitude-digital converter with impulsing circuit  

International Nuclear Information System (INIS)

The authors describe an amplitude digital converter with logarithmic response. The converter has two functional units. The first, located in or near the housing of the photomultiplier, converts the short negative pulse from the photomultiplier into a train of pulses of standard height and frequency. The second, placed in a standard CAMAC module, consists of a differential receiver, switch, counter, and commutator. Input pulses have a width of 0.3 microseconds and a height of 150 microvolts - 10 V. Conversion discreteness is 10% and the counter has seven bits. Conversion time is less than 128 microseconds. The error is less than 10% for an ambient temperature of +50 to -300C

243

Fringe free holographic measurements of large amplitude vibrations  

CERN Document Server

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.

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

2010-01-01

244

On the Period-Amplitude and Amplitude-Period Relationships  

Science.gov (United States)

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.

Wilson, Robert M.; Hathaway, David H.

2008-01-01

245

Tyrosine 50 at the subunit interface of dimeric human glutathione transferase P1-1 is a structural key residue for modulating protein stability and catalytic function.  

Science.gov (United States)

The dimer interface in human GSTP1-1 has been altered by site-directed mutagenesis of Tyr50. It is shown that the effects of some mutations of this single amino acid residue are as detrimental for enzyme function as mutations of Tyr8 in the active site. The dimeric structure is a common feature of the soluble glutathione transferases and the structural lock-and-key motif contributing to the subunit-subunit interface is well conserved in classes alpha, mu, and pi. The key residue Tyr50 in GSTP1-1 was replaced with 5 different amino acids with divergent properties and the mutant proteins expressed and characterized. Mutant Y50F is an improved variant, with higher thermal stability and higher catalytic efficiency than the wild-type enzyme. The other mutants studied are also dimeric proteins, but have lower stabilities and catalytic activities that are reduced by a factor of 10(2)-10(4) from the wild-type value. Mutants Y50L and Y50T are characterized by a markedly increased K(M) value for GSH, while the effect is mainly due to decreased k(cat) values for mutants Y50A and Y50R. In conclusion, residue 50 in the interface governs both structural stability and catalytic function. PMID:10777681

Stenberg, G; Abdalla, A M; Mannervik, B

2000-04-29

246

Optical modulation transfer by molecular modulation  

International Nuclear Information System (INIS)

Modulation features in the frequency domain can be transferred from an amplitude-modulated laser field to a nonmodulated one by a strong Raman coupling, which is based on refractive index control with a strong Raman coherence established with two sufficiently intense laser fields slightly off the two-photon Raman resonance of a selected Raman mode. Numerical simulations show that modulation transfers between the driving lasers, such as transfers from ultraviolet to extreme ultraviolet and from infrared to middle infrared lasers, can be realized in gaseous Raman media. This provides an efficient way to extend the optical modulation range beyond the transparent ranges of commercial modulators. Modulation features can also be transferred from a low-intensity driving laser to a high-intensity one, which ensures a direct application to modulate lasers with high intensities beyond the damage thresholds of standard modulators

247

Evolution kernels from splitting amplitudes  

International Nuclear Information System (INIS)

We recalculate the next-to-leading order Altarelli-Parisi kernel using a method which relates it to the splitting amplitudes describing the collinear factorization properties of scattering amplitudes. The method breaks up the calculation of the kernel into individual pieces which have an independent physical interpretation

248

Evolution Kernels from Splitting Amplitudes  

CERN Document Server

We recalculate the next-to-leading order Altarelli-Parisi kernel using a method which relates it to the splitting amplitudes describing the collinear factorization properties of scattering amplitudes. The method breaks up the calculation of the kernel into individual pieces which have an independent physical interpretation.

Kosower, D A; Kosower, David A.; Uwer, Peter

2003-01-01

249

The pulsed amplitude unit for the SLC  

International Nuclear Information System (INIS)

There is a recurring requirement in the SLC for the control of devices such as magnets, phase shifters, and attenuators on a beam-by-beam basis. The Pulsed Amplitude Unit (PAU) is a single width CAMAC module developed for this purpose. It provides digitally programmed analog output voltages on a beam-by-beam basis. Up to 32 preprogrammed values of output voltage are available from the single analog output of the module, and any of these values can be associated with any of the 256 possible SLC beam definitions. A 12-bit Analog-to-Digital converter (ADC) digitizes an analog input signal at the appropriate beam time and stores it in a buffer memory. This feature is normally used to monitor the response of the device being controlled by the PAU at each beam time. Initial application of the PAU at is as part of the system that controls the output of Klystorns in the SLC. The PAU combines several different functions in a single module. In order to accommodate these functions in a single width CAMAC module, field programmed logic is used extensively. Field Programmable Logic Arrays, Programmed Array Logic, and a Field Programmable Logic Sequencer are employed

250

Residual stresses  

International Nuclear Information System (INIS)

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

251

Amplitude path corrections for regional phases in China  

Energy Technology Data Exchange (ETDEWEB)

The authors investigate the effectiveness of amplitude path corrections for regional phases on seismic event discrimination and magnitude estimation. Waveform data from digital stations in China for regional, shallow (< 50 km) events were obtained from the IRIS Data Management Center (DMC) for years 1986 to 1996 using the USGS Preliminary Determination of Epicenters (PDE) and the Chinese State Seismological Bureau (SSB) catalogs. For each event, the amplitudes for each regional phase (P{sub n}, P{sub g}, S{sub n}, L{sub g}) were measured, as well as the P{sub g} and L{sub g} coda. Measured amplitudes were corrected for source scaling using estimates of m{sub b} and for distance using a power law that accounts for attenuation and spreading. The amplitude residuals were interpolated and mapped as 2-D amplitude correction surfaces. The authors employ several methods to create the amplitude correction surfaces: a waveguide method, and two interpolation methods (Baysian kriging and a circular moving window mean smoother). They explore the sensitivities of the surfaces to the method and to regional propagation, and apply these surfaces to correct amplitude data to reduce scatter in discrimination ratios and magnitude estimates.

Phillips, W.S.; Velasco, A.A.; Taylor, S.R.; Randall, G.E.

1998-12-31

252

Cavity enhanced terahertz modulation  

International Nuclear Information System (INIS)

We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%

253

Cavity enhanced terahertz modulation  

Energy Technology Data Exchange (ETDEWEB)

We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%.

Born, N., E-mail: norman.born@physik.uni-marburg.de [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States); Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany); Scheller, M.; Moloney, J. V. [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States); Koch, M. [Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany)

2014-03-10

254

Ultrasoft amplitudes in hot QCD  

International Nuclear Information System (INIS)

By using the Boltzmann equation describing the relaxation of colour excitations in the QCD plasma, we obtain effective amplitudes for the ultrasoft colour fields carrying momenta of order g2T. These amplitudes are of the same order in g as the hard thermal loops (HTL), which they generalize by including the effects of the collisions among the hard particles. The ultrasoft amplitudes share many of the remarkable properties of the HTL's: they are gauge invariant, obey simple Ward identities, and, in the static limit, reduce to the usual Debye mass for the electric fields. However, unlike the HTL's, which correspond effectively to one-loop diagrams, the ultrasoft amplitudes resum an infinite number of diagrams of the bare perturbation theory. By solving the linearized Boltzmann equation, we obtain a formula for the colour conductivity which accounts for the contributions of the hard and soft modes beyond the leading logarithmic approximation

255

Approximating chiral SU(3) amplitudes  

Energy Technology Data Exchange (ETDEWEB)

We construct large-N{sub c} 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 N{sup 3}LO 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 F{sub 0}, the meson decay constant in the chiral SU(3) limit, that is more precise than all presently available determinations. (orig.)

Ecker, G.; Neufeld, H. [University of Vienna, Faculty of Physics, Vienna (Austria); Masjuan, P. [Johannes Gutenberg-Universitaet, Institut fuer Kernphysik, Mainz (Germany)

2014-02-15

256

Amplitude and frequency readout overlay  

Science.gov (United States)

Amplitude and frequency readout overlay simplifies the interpretation of oscillograph traces for full scale deflections of one inch. The overlay increases accuracy in data interpretation and saves time in analyzing oscillograph records.

Fitch, A. E.

1968-01-01

257

Residual stresses  

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.)

258

Large amplitude oscillations in prominences  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Tripathi, D.; Isobe, H.; Jain, R.

2009-01-01

259

Pion photoproduction and ?N ? ? amplitudes  

International Nuclear Information System (INIS)

The authors review a dynamical model for the pion photoproduction on the nucleon. With the model, they explore sensitivities of observables to the E2 (or E1+) multipole amplitude in the ?N ? ? transition. It will be demonstrated that the cross section with polarized photons has a significant sensitivity to the E2 amplitude. The model prediction will be compared with the most recent LEGS data. 15 refs., 7 figs

260

Sensitivity to changes in amplitude envelope  

Science.gov (United States)

Detection of a brief increment in a tonal pedestal is less well predicted by energy-detection (e.g., Macmillan, 1973; Bonnel and Hafter, 1997) than by sensitivity to changes in the stimulus envelope. As this implies a mechanism similar to an envelope extractor (Viemeister, 1979), sinusoidal amplitude modulation was used to mask a single ramped increment (10, 45, or 70 ms) added to a 1000-ms pedestal with carrier frequency (cf)=477 Hz. As in informational masking (Neff, 1994) and ``modulation-detection interference'' (Yost and Sheft, 1989), interference occurred with masker cfs of 477 and 2013 Hz. While slight masking was found with modulation frequencies (mfs) from 16 to 96 Hz, masking grew inversely with still lower mfs, being greatest for mf=4 Hz. This division is reminiscent of that said to separate sensations of ``roughness'' and ``beats,'' respectively (Terhardt, 1974), with the latter also being related to durations associated with auditory groupings in music and speech. Importantly, this result held for all of the signal durations and onset-offset ramps tested, suggesting that an increment on a pedestal is treated as a single auditory object whose detection is most difficult in the presence of other objects (in this case, ``beats'').

Gallun, Erick; Hafter, Ervin R.; Bonnel, Anne-Marie

2002-05-01

 
 
 
 
261

Amino acid residues that flank core peptide epitopes and the extracellular domains of CD4 modulate differential signaling through the T cell receptor.  

Science.gov (United States)

Hen egg lysozyme 52-61-specific CD4+ T cells responded by interleukin 2 (IL-2) secretion to any peptide containing this epitope regardless of length of NH2- and COOH-terminal composition. However, CD4- variants could only respond to peptides containing the two COOH-terminal tryptophans at positions 62 and 63. Substitutions at these positions defined patterns of reactivity that were specific for individual T cells inferring a T cell receptor (TCR)-based phenomenon. Thus, the fine specificity of major histocompatibility complex (MHC)-peptide recognition by the TCR was dramatically affected by CD4 and the COOH-terminal peptide composition. Peptides that failed to induce IL-2 secretion in the CD4- variants nevertheless induced strong tyrosine phosphorylation of CD3 zeta. Thus, whereas the TCR still recognized and bound to the MHC class II-peptide complex resulting in protein phosphorylation, this interaction failed to induce effective signal transduction manifested by IL-2 secretion. This provides a clear example of differential signaling mediated by peptides known to be naturally processed. In addition, the external domains of CD4, rather than its cytoplasmic tail, were critical in aiding TCR recognition of all peptides derived from a single epitope. These data suggest that the nested flanking residues, which are present on MHC class II but not class I bound peptides, are functionally relevant. PMID:7515103

Vignali, D A; Strominger, J L

1994-06-01

262

A lysine residue in the fingers subdomain of T7 DNA polymerase modulates the miscoding potential of 8-oxo-7,8-dihydroguanosine.  

Science.gov (United States)

8-oxo-7,8-dihydroguanosine (8oG) is a highly mutagenic DNA lesion that stably pairs with adenosine, forming 8oG(syn).dA(anti) Hoogsteen base pairs. DNA polymerases show different propensities to insert dCMP or dAMP opposite 8oG, but the molecular mechanisms that determine faithful or mutagenic bypass are poorly understood. Here, we report kinetic and structural data providing evidence that, in T7 DNA polymerase, residue Lys536 is responsible for attenuating the miscoding potential of 8oG. The Lys536Ala polymerase shows a significant increase in mutagenic 8oG bypass versus wild-type polymerase, and a crystal structure of the Lys536Ala mutant reveals a closed complex with an 8oG(syn).dATP mismatch in the polymerase active site, in contrast to the unproductive, open complex previously obtained by using wild-type polymerase. We propose that Lys536 acts as a steric and/or electrostatic filter that attenuates the miscoding potential of 8oG by normally interfering with the binding of 8oG in a syn conformation that pairs with dATP. PMID:16271888

Brieba, Luis G; Kokoska, Robert J; Bebenek, Katarzyna; Kunkel, Thomas A; Ellenberger, Tom

2005-11-01

263

Phasor-Difference Method for Measuring the Amplitude and the Phase of Small-Amplitude Vibrations with TV Holography.  

Science.gov (United States)

A new, to the author's knowledge, method for time-averaged TV holography measurements of small-amplitude vibrations is presented. In time-averaged TV holography with sinusoidal phase modulation of the reference arm of the interferometer, two phasors describe the object vibration and the modulation of the reference arm. By inversion of the squared zero-order Bessel function of the first kind, it is possible to measure the distance between these two phasors. The distances from an object-vibration phasor to a number of known reference phasors are measured to determine the amplitude and the phase of the object vibration. The method is demonstrated by the measurement of a vibration mode of a circular metal disk. The results are compared with theoretical data and with data obtained by a commonly used method in phase-modulated TV holography. PMID:18286020

Rustad, R

1998-08-10

264

Phasor-Difference Method for Measuring the Amplitude and the Phase of Small-Amplitude Vibrations with TV Holography  

Science.gov (United States)

A new, to the author s knowledge, method for time-averaged TV holography measurements of small-amplitude vibrations is presented. In time-averaged TV holography with sinusoidal phase modulation of the reference arm of the interferometer, two phasors describe the object vibration and the modulation of the reference arm. By inversion of the squared zero-order Bessel function of the first kind, it is possible to measure the distance between these two phasors. The distances from an object-vibration phasor to a number of known reference phasors are measured to determine the amplitude and the phase of the object vibration. The method is demonstrated by the measurement of a vibration mode of a circular metal disk. The results are compared with theoretical data and with data obtained by a commonly used method in phase-modulated TV holography.

Rustad, Rolf

1998-08-01

265

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

LENUS (Irish Health Repository)

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.

Adamson, Justus

2012-02-01

266

Mapping Pn amplitude spreading and attenuation in Asia  

Energy Technology Data Exchange (ETDEWEB)

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.

Yang, Xiaoning [Los Alamos National Laboratory; Phillips, William S [Los Alamos National Laboratory; Stead, Richard J [Los Alamos National Laboratory

2010-12-06

267

N=4 scattering amplitudes and the deformed Graßmannian  

Science.gov (United States)

Some time ago the general tree-level scattering amplitudes of N=4 Super Yang-Mills theory were expressed as certain Graßmannian contour integrals. These remarkable formulas allow to clearly expose the super-conformal, dual super-conformal, and Yangian symmetries of the amplitudes. Using ideas from integrability it was recently shown that the building blocks of the amplitudes permit a natural multi-parameter deformation. However, this approach had been criticized by the observation that it seemed impossible to reassemble the building blocks into Yangian-invariant deformed non-MHV amplitudes. In this note we demonstrate that the deformations may be succinctly summarized by a simple modification of the measure of the Graßmannian integrals, leading to a Yangian-invariant deformation of the general tree-level amplitudes. Interestingly, the deformed building blocks appear as residues of poles in the spectral parameter planes. Given that the contour integrals also contain information on the amplitudes at loop-level, we expect the deformations to be useful there as well. In particular, applying meromorphicity arguments, they may be expected to regulate all notorious infrared divergences. We also point out relations to Gelfand hypergeometric functions and the quantum Knizhnik-Zamolodchikov equations.

Ferro, Livia; ?ukowski, Tomasz; Staudacher, Matthias

2014-12-01

268

Scattering amplitudes and Wilson loops in twistor space  

Energy Technology Data Exchange (ETDEWEB)

This paper reviews the recent progress in twistor approaches to Wilson loops, amplitudes and their duality for N=4 super-Yang-Mills. Wilson loops and amplitudes are derived from first principles using the twistor action for maximally supersymmetric Yang-Mills theory. We start by deriving the MHV rules for gauge theory amplitudes from the twistor action in an axial gauge in twistor space, and show that this gives rise to the original momentum space version given by Cachazo, Svrcek and Witten. We then go on to obtain from these the construction of the momentum twistor space loop integrand using (planar) MHV rules and show how it arises as the expectation value of a holomorphic Wilson loop in twistor space. We explain the connection between the holomorphic Wilson loop and certain light-cone limits of correlation functions. We give a brief review of other ideas in connection with amplitudes in twistor space: twistor-strings, recursion in twistor space, the Grassmannian residue formula for leading singularities and amplitudes as polytopes. This paper is an invited review for a special issue of Journal of Physics A: Mathematical and Theoretical devoted to 'Scattering amplitudes in gauge theories'. (review)

Adamo, Tim; Mason, Lionel [Mathematical Institute, 24-29 St. Giles' , Oxford OX1 3LB (United Kingdom); Bullimore, Mathew [Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP (United Kingdom); Skinner, David, E-mail: adamo@maths.ox.ac.uk [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2 L 2Y5 (Canada)

2011-11-11

269

Topological amplitudes in string theory  

International Nuclear Information System (INIS)

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

270

A Regge Model for Nucleon-Nucleon Scattering Amplitudes  

Science.gov (United States)

We present a model to calculate nucleon-nucleon (NN) scattering amplitudes, at laboratory kinetic energies greater than 1.3 GeV. The model, based on Regge theory, is fully relativistic, and exhibits full spin dependence. We relate the Regge exchanges to the Fermi invariants, which gives an organized and simplified method to incorporate Regge exchanges into the NN scattering. An added benefit is that all spin dependence is explicitly dealt with. The parameters in the model are from the Regge trajectories, which are obtained from the meson spectrum, and the residues. We employ phenomenological residues, which we determine by fitting our model to total and differential cross section data, and the SAID helicity amplitudes. Preliminary results are presented.

Ford, William; van Orden, J. Wallace

2010-11-01

271

Multidimensional signal modulation and/or demodulation for data communications  

Science.gov (United States)

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.

Smith, Stephen F. (London, TN); Dress, William B. (Camas, WA)

2008-03-04

272

Variable amplitude fatigue crack growth behavior - a short overview  

International Nuclear Information System (INIS)

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

273

Master equations for master amplitudes  

Energy Technology Data Exchange (ETDEWEB)

The general lines of the derivation and the main properties of the master equations for the master amplitudes associated to a given Feynman graph are recalled. Some results for the 2-loop self mass graph with 4 propagators are presented. (author) 5 refs, 1 fig

Caffo, M. [INFN, Sezione di Bologna, Bologna (Italy)]|[Dipartimento di Fisica, Universita di Bologna, Bologna (Italy); Czyz, H. [Institute of Physics, University of Silesia, Katowice (Poland); Laporta, S. [Dipartimento di Fisica, Universita di Bologna, Bologna (Italy); Remiddi, E. [Dipartimento di Fisica, Universita di Bologna, Bologna (Italy)]|[INFN, Sezione di Bologna, Bologna (Italy)

1998-10-01

274

Distribution amplitudes of pseudoscalar mesons  

Energy Technology Data Exchange (ETDEWEB)

We present results for the first two moments of the distribution amplitudes of pseudoscalar mesons. Using two flavors of non-perturbatively improved clover fermions and non-perturbative renormalization of the matrix elements we perform both chiral and continuum extrapolations and compare with recent results from models and experiments. (orig.)

Braun, V.M.; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)

2006-10-15

275

Distribution amplitudes of vector mesons  

Energy Technology Data Exchange (ETDEWEB)

Results are presented for the lowest moment of the distribution amplitude for the K{sup *} vector meson. Both longitudinal and transverse moments are investigated. We use two flavours of O(a) improved Wilson fermions, together with a non-perturbative renormalisation of the matrix element. (orig.)

Braun, V.M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Broemmel, D. [Deutsches Elektronen-Synchrotron, Hamburg (Germany); Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

2007-11-15

276

Scattering amplitudes in gauge theories  

Energy Technology Data Exchange (ETDEWEB)

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.

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

277

Complete Determination of Reaction Amplitudes  

Science.gov (United States)

The reaction amplitudes for a+b?c+d, with arbitrary spins jv, are completely determined if one carries out measurements of a subset of final state spin correlation parameters t{q_c qd {kc kd } ( s ; ) where the index ‘s’ denotes appropriate initial spin preparations.

Ramachandran, G.; Sandhya, S. N.

278

K anti K amplitude analyses  

International Nuclear Information System (INIS)

A review is presented of amplitude analyses of the K anti K system produced in reactions of the type ?/sup +-/N ? K anti KN. These analyses establish the existence of a new S-wave K anti K state at a mass of approximately 1300 MeV, having isospin 0 and a slow phase variation

279

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

Science.gov (United States)

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

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

2014-09-01

280

Implementation of Phase-only Modulation Utilizing a Twisted Nematic Liquid Crystal Spatial Light Modulator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Twisted nematic liquid crystal spatial light modulators, (SLM) are widely used for amplitude modulation of light. The technique for measuring phase and amplitude modulation introduced by a twisted nematic cell is not new but the novelty here is that after characterisation of a Holoeye LC2002 TNLC device we were able to identify specific conditions that allow for its use as a pure 180 degree or more, phase modulator with little or no amplitude modulation at 514.5 nm laser wavelength. The phase...

Mahmud, Mohammad; Naydenova, Izabela; Toal, Vincent

2008-01-01

 
 
 
 
281

High Amplitude Secondary Mass Drive  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-07-06

282

Observing rapid quasi-wave ionospheric disturbance using amplitude charts  

Science.gov (United States)

Data from vertical (quasi-vertical) sounding are traditionally used for determining a number of ionospheric parameters such as critical frequencies of E and F layers, peaks of these layers, and for reconstructing electron density profiles. In this respect, radio sounding is not used to its full capacity. Modern ionosondes provide additional information encoded in ionospheric echoes, including information on reflected-signal amplitude. The time dependence of the amplitude-frequency characteristic of reflected signal has been named "amplitude chart" (A-chart). Ionosondes used by the ISTP SB RAS Geophysical Observatory for constructing A-charts employ the frequency-modulated continuous-wave (FMCW) signal in a range 1.3-15 MHz. One-minute sounding interval allows a more detailed study of dynamic processes in the ionosphere. The ionosonde has a direct digital synthesizer and direct sampling receiver without automatic gain control (AGC). The absence of AGC and the high dynamic range enable determination of the relative field strength at a receiving point and registration of relative long-term variations in reflected-signal amplitude over the entire range of operating frequencies of the ionosonde. We have revealed that the passage of travelling ionospheric disturbances (TID) along with height-frequency distortion modulates amplitude characteristics of signal. The characteristic depth of the modulation reaches 40 dB. The pronounced alternate vertical stripes typical for A-charts are likely to be associated with focusing properties of TID. In order to examine the space-time structure of TID able to induce such a focusing of the radio waves, we performed ray tracing simulations. We used geometrical-optics approximation, took magneto-ionic effects into account and prescribed electron density to be a stratified electron density profile on which an undulating disturbance was superimposed. This work was supported by the RFBR grant ?14-05-00259-?.

Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey

283

Amplitude dropout in coupled lasers  

International Nuclear Information System (INIS)

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

284

Infinities within graviton scattering amplitudes  

CERN Document Server

We present unitarity as a method for determining the infinities present in graviton scattering amplitudes. The infinities are a combination of IR and UV. By understanding the soft singularities we may extract the UV infinities and relate these to counter-terms in the effective action. As an demonstration of this method we rederive the UV infinities present at one-loop when gravity is coupled to matter.

Dunbar, D C

1995-01-01

285

Phase variation of hadronic amplitudes  

International Nuclear Information System (INIS)

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

286

Residual basins  

International Nuclear Information System (INIS)

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

287

Quantitative analysis by X-ray fractography of fatigue fractured surface under variable amplitude loading  

International Nuclear Information System (INIS)

X-ray fractography is a method of analysing the causes of accidental fracture of machine components or structures. Almost all of the previous research on this problem has been carried out using constant amplitude fatigue tests. However, the actual loads on components and structures are usually of variable amplitudes. In this study, X-ray fractography was applied to fatigue fractured surfaces produced by variable amplitude loading. Fatigue tests were carried out on Ni-Cr-Mo steel CT specimens under the conditions of repeated, two-step and multiple-step loading. Residual stresses were measured on the fatigue fractured surface by an X-ray diffraction method. The relationships between residual stress and stress intensity factor or crack propagation rate were studied. They were discussed in terms of the quantitative expressions under constant amplitude loading, proposed by the authors in previous papers. The main results obtained were as follows : (1) It was possible to estimate the crack propagation rate of the fatigue fractured surface under variable amplitude loading by using the relationship between residual stress and stress intensity factor under constant amplitude loading. (2) The compressive residual stress components on the fatigue fractured surface correspond with cyclic softening of the material rather than with compressive plastic deformation at the crack tip. (author)

288

Quadratic constraints in amplitude analysis  

Energy Technology Data Exchange (ETDEWEB)

The quadratic constraints among bilinear products of reaction amplitudes for a reaction with arbitrary spins are discussed in terms of the experimental observables. While the specific form of these constraints may be quite lengthy, the optimal formalism of polarization phenomena exhibits the structure of these constraints transparently and gives a systematic procedure to calculate them. Some general features of these constraints are exhibited which are useful for planning experiments. Such features can be recognized without the lengthy calculations, with the help of a diagrammatic analog combined with the transparent structure of the optimal formalism.

Moravcsik, M.J.

1983-01-01

289

Quadratic constraints in amplitude analysis  

Energy Technology Data Exchange (ETDEWEB)

The quadratic constraints among bilinear products of reaction amplitudes for a reaction with arbitrary spins are discussed in terms of the experimental observables. While the specific form of these constraints may be quite lengthy, the optimal formalism of polarization phenomena exhibits the structure of these constraints transparently and gives a systematic procedure to calculate them. Some general features of these constraints are exhibited which are useful for planning experiments. Such features can be recognized without lengthy calculations, with the help of a diagrammatic analog combined with the transparent structure of the optimal formalism.

Moravcsik, M.J.

1984-06-01

290

Superstring amplitudes and contact interactions  

International Nuclear Information System (INIS)

We show that scattering amplitudes computed from light-cone superstring field theory are divergent at tree level. The divergences can be eliminated, and supersymmetry restored, by the addition of certain counter terms to the light-cone Hamiltonian. These counter terms have the form of local contact interactions, whose existence we had previously deduced on grounds of vacuum stability, and closure of the super-Poincare algebra. The quartic contact interactions required in Type I and Type IIB superstring theories are constructed in detail. (orig.)

291

Complete determination of reaction amplitudes  

Energy Technology Data Exchange (ETDEWEB)

The reaction amplitudes for a + b ..-->.. c + d, with arbitrary spins j/sub v/, are completely determined if one carries out measurements of a subset of final state spin correlation parameters t/sub q/c/sub //sup k/sub c///sub q/d/sub //sup k/sub d//(s) where the index 's' denotes appropriate initial spin preparations.

Ramachandran, G.; Sandhya, S.N.

1988-09-01

292

The modulation instability revisited  

Science.gov (United States)

The modulational instability (or “Benjamin-Feir instability”) has been a fundamental principle of nonlinear wave propagation in systems without dissipation ever since it was discovered in the 1960s. It is often identified as a mechanism by which energy spreads from one dominant Fourier mode to neighboring modes. In recent work, we have explored how damping affects this instability, both mathematically and experimentally. Mathematically, the modulational instability changes fundamentally in the presence of damping: for waves of small or moderate amplitude, damping (of the right kind) stabilizes the instability. Experimentally, we observe wavetrains of small or moderate amplitude that are stable within the lengths of our wavetanks, and we find that the damped theory predicts the evolution of these wavetrains much more accurately than earlier theories. For waves of larger amplitude, neither the standard (undamped) theory nor the damped theory is accurate, because frequency downshifting affects the evolution in ways that are still poorly understood.

Segur, H.; Henderson, D. M.

2007-08-01

293

Multilevel Modulation formats for Optical Communication  

DEFF Research Database (Denmark)

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

Jensen, Jesper Bevensee

2008-01-01

294

Augmented Recursion For One-loop Amplitudes  

International Nuclear Information System (INIS)

We present a semi-recursive method for calculating the rational parts of one-loop amplitudes when recursion produces double poles. We illustrate this with the graviton scattering amplitude M1-loop(1-,2+,3+,4+,5+).

295

Constructing Amplitudes from Their Soft Limits  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-12-09

296

Augmented Recursion For One-loop Amplitudes  

CERN Document Server

We present a semi-recursive method for calculating the rational parts of one-loop amplitudes when recursion produces double poles. We illustrate this with the graviton scattering amplitude M^{1-loop}(1-, 2+, 3+, 4+, 5+).

Dunbar, David C; Perkins, Warren B

2010-01-01

297

Similarities of gauge and gravity amplitudes  

CERN Document Server

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.

Bjerrum-Bohr, N E J; Ita, H; Dunbar, David C.; Ita, Harald

2006-01-01

298

Determination of backward pion nucleon scattering amplitudes  

International Nuclear Information System (INIS)

Backward C(sup(+-))?N amplitudes are determined from ?N?N? and NantiN?2? differential cross sections in such a way that they are consistent with the analyticity properties and information of the unphysical ???NantiN amplitudes. Combining the result with forward C(sup(+-)) amplitudes positive and negative parity resonances are extracted. An error analysis of the amplitudes is performed. (author)

299

Frequency-modulation spectroscopy of rubidium atoms with an AlGaAs diode laser.  

Science.gov (United States)

Frequency-modulation (FM) spectroscopy has been performed on the D(2) transitions of rubidium atoms with an AlGaAs diode laser at 780 nm. Doppler-broadened hyperfine-structure transitions of (85)Rb and (87)Rb were resolved with no residual amplitude-modulation-induced background signal by modulating the injection current of the laser diode at a low frequency (20-50 MHz) compared with the Doppler width. To obtain Doppler-free spectra, we combined FM spectroscopy with saturation spectroscopy. The results show that the FM spectroscopy technique is sensitive and should be useful for high-resolution spectroscopy, although the resolution was instrument limited and unusual double peaks were observed. PMID:19741897

Nakanishi, S; Ariki, H; Itoh, H; Kondo, K

1987-11-01

300

Holonomy-flux spinfoam amplitude  

CERN Document Server

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

Perini, Claudio

2012-01-01

 
 
 
 
301

Amplitude control of quantum interference  

CERN Document Server

Usually, the oscillations of interference effects are controlled by relative phases. We show that varying the amplitudes of quantum waves, for instance by changing the reflectivity of beam splitters, can also lead to quantum oscillations and even to Bell violations of local realism. We first study theoretically a generalization of the Hong-Ou-Mandel experiment to arbitrary source numbers and beam splitter transmittivity. We then consider a Bell type experiment with two independent sources, and find strong violations of local realism for arbitrarily large source number $N$; for small $N$, one operator measures essentially the relative phase of the sources and the other their intensities. Since, experimentally, one can measure the parity of the number of atoms in an optical lattice more easily than the number itself, we assume that the detectors measure parity.

Mullin, W J

2011-01-01

302

Amplitude control of quantum interference  

Science.gov (United States)

Usually, the oscillations of interference effects are controlled by relative phases. We show that varying the amplitudes of quantum waves, for instance by changing the reflectivity of beam splitters, can also lead to quantum oscillations and even to Bell violations of local realism. We first study theoretically a generalization of the Hong-Ou-Mandel experiment to arbitrary source numbers and beam-splitter transmittivity. We then consider a Bell-type experiment with two independent sources and find strong violations of local realism for arbitrarily large source number N; for small N, one operator measures essentially the relative phase of the sources and the other their intensities. Since, experimentally, one can measure the parity of the number of atoms in an optical lattice more easily than the number itself, we assume that the detectors measure parity.

Mullin, W. J.; Laloë, F.

2012-02-01

303

Quantum mechanics without probability amplitudes  

International Nuclear Information System (INIS)

First steps are taken toward a formulation of quantum mechanics which avoids the use of probability amplitudes and is expressed entirely in terms of observable probabilities. Quantum states are represented not by state vectors or density matrices but by ''probability tables,'' which contain only the probabilities of the outcomes of certain special measurements. The rule for computing transition probabilities, normally given by the squared modulus of the inner product of two state vectors, is re-expressed in terms of probability tables. The new version of the rule is surprisingly simple, especially when one considers that the notion of complex phases, so crucial in the evaluation of inner products, is entirely absent from the representation of states used here

304

Higher Codimension Singularities Constructing Yang-Mills Tree Amplitudes  

CERN Document Server

Yang-Mills tree-level amplitudes contain singularities of codimension one like collinear and multi-particle factorizations, codimension two such as soft limits, as well as higher codimension singularities. Traditionally, BCFW-like deformations with one complex variable were used to explore collinear and multi-particle channels. Higher codimension singularities need more complex variables to be reached. In this paper, along with a discussion on higher singularities and the role of the global residue theorem in this analysis, we specifically consider soft singularities. This is done by extending Risager's deformation to a $\\mathbb C^2$-plane, i.e., two complex variables. The two-complex-dimensional deformation is then used to recursively construct Yang-Mills tree amplitudes.

Rajabi, Sayeh

2011-01-01

305

Calculation of pulse amplitude in nuclear magnetic logging  

International Nuclear Information System (INIS)

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

306

47 CFR 2.201 - Emission, modulation, and transmission characteristics.  

Science.gov (United States)

...angle-modulated during the period of the pulse Q —Which is a combination...following modes: amplitude, angle, pulse W (7) Cases not otherwise...coded into quantized form (e.g. pulse code modulation) should be designated...

2010-10-01

307

Quantum Amplitude Amplification and Estimation  

CERN Document Server

Consider a Boolean function $\\chi: X \\to \\{0,1\\}$ that partitions set $X$ between its good and bad elements, where $x$ is good if $\\chi(x)=1$ and bad otherwise. Consider also a quantum algorithm $\\mathcal A$ such that $A \\ket{0} = \\sum_{x\\in X} \\alpha_x \\ket{x}$ is a quantum superposition of the elements of $X$, and let $a$ denote the probability that a good element is produced if $A \\ket{0}$ is measured. If we repeat the process of running $A$, measuring the output, and using $\\chi$ to check the validity of the result, we shall expect to repeat $1/a$ times on the average before a solution is found. *Amplitude amplification* is a process that allows to find a good $x$ after an expected number of applications of $A$ and its inverse which is proportional to $1/\\sqrt{a}$, assuming algorithm $A$ makes no measurements. This is a generalization of Grover's searching algorithm in which $A$ was restricted to producing an equal superposition of all members of $X$ and we had a promise that a single $x$ existed such tha...

Brassard, G; Mosca, M; Tapp, A; Brassard, Gilles; Hoyer, Peter; Mosca, Michele; Tapp, Alain

2000-01-01

308

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 correlations, but shows only a weak dependence on temperature between 0 and 300 K

309

Is the effect of tinnitus on auditory steady-state response amplitude mediated by attention?  

Directory of Open Access Journals (Sweden)

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.

EugenDiesch

2012-05-01

310

Understanding and Ameliorating Non-Linear Phase and Amplitude Responses in AMCW Lidar  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 othe...

Godbaz, John P.; Dorrington, Adrian A.; Cree, Michael J.

2011-01-01

311

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

International Nuclear Information System (INIS)

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

312

Enhancing Chinese tone recognition by manipulating amplitude envelope: Implications for cochlear implants  

Science.gov (United States)

Tone recognition is important for speech understanding in tonal languages such as Mandarin Chinese. Cochlear implant patients are able to perceive some tonal information by using temporal cues such as periodicity-related amplitude fluctuations and similarities between the fundamental frequency (F0) contour and the amplitude envelope. The present study investigates whether modifying the amplitude envelope to better resemble the F0 contour can further improve tone recognition in multichannel cochlear implants. Chinese tone and vowel recognition were measured for six native Chinese normal-hearing subjects listening to a simulation of a four-channel cochlear implant speech processor with and without amplitude envelope enhancement. Two algorithms were proposed to modify the amplitude envelope to more closely resemble the F0 contour. In the first algorithm, the amplitude envelope as well as the modulation depth of periodicity fluctuations was adjusted for each spectral channel. In the second algorithm, the overall amplitude envelope was adjusted before multichannel speech processing, thus reducing any local distortions to the speech spectral envelope. The results showed that both algorithms significantly improved Chinese tone recognition. By adjusting the overall amplitude envelope to match the F0 contour before multichannel processing, vowel recognition was better preserved and less speech-processing computation was required. The results suggest that modifying the amplitude envelope to more closely resemble the F0 contour may be a useful approach toward improving Chinese-speaking cochlear implant patients' tone recognition. .

Luo, Xin; Fu, Qian-Jie

2004-12-01

313

Inhibition of synaptic transmission and G protein modulation by synthetic CaV2.2 Ca2+ channel peptides  

Science.gov (United States)

Abstract Modulation of presynaptic voltage-dependent Ca2+ channels is a major means of controlling neurotransmitter release. The CaV2.2 Ca2+ channel subunit contains several inhibitory interaction sites for G?? subunits, including the amino terminal (NT) and I–II loop. The NT and I–II loop have also been proposed to undergo a G protein-gated inhibitory interaction, whilst the NT itself has also been proposed to suppress CaV2 channel activity. Here, we investigate the effects of an amino terminal (CaV2.2[45–55]) ‘NT peptide’ and a I–II loop alpha interaction domain (CaV2.2[377–393]) ‘AID peptide’ on synaptic transmission, Ca2+ channel activity and G protein modulation in superior cervical ganglion neurones (SCGNs). Presynaptic injection of NT or AID peptide into SCGN synapses inhibited synaptic transmission and also attenuated noradrenaline-induced G protein modulation. In isolated SCGNs, NT and AID peptides reduced whole-cell Ca2+ current amplitude, modified voltage dependence of Ca2+ channel activation and attenuated noradrenaline-induced G protein modulation. Co-application of NT and AID peptide negated inhibitory actions. Together, these data favour direct peptide interaction with presynaptic Ca2+ channels, with effects on current amplitude and gating representing likely mechanisms responsible for inhibition of synaptic transmission. Mutations to residues reported as determinants of Ca2+ channel function within the NT peptide negated inhibitory effects on synaptic transmission, Ca2+ current amplitude and gating and G protein modulation. A mutation within the proposed QXXER motif for G protein modulation did not abolish inhibitory effects of the AID peptide. This study suggests that the CaV2.2 amino terminal and I–II loop contribute molecular determinants for Ca2+ channel function; the data favour a direct interaction of peptides with Ca2+ channels to inhibit synaptic transmission and attenuate G protein modulation. PMID:21521766

Bucci, Giovanna; Mochida, Sumiko; Stephens, Gary J

2011-01-01

314

Higher-order solitons in amplitude-disordered waveguide arrays  

Science.gov (United States)

We investigate the existence and stability of different families of spatial solitons in optical waveguide arrays whose amplitudes obey a disordered distribution. The competition between focusing nonlinearity and linearly disordered refractive index modulation results in the formation of spatial localized nonlinear states. Solitons originating from Anderson modes with few nodes are robust during propagation. While multi-peaked solitons with in-phase neighboring components are completely unstable, multipole-mode solitons whose neighboring components are out-of-phase can propagate stably in wide parameter regions provided that their power exceeds a critical value. Our findings, thus, provide the first example of stable higher-order nonlinear states in disordered systems.

Liu, Hai-Dong; Jin, Hong-Zhen; Dong, Liang-Wei

2014-10-01

315

Nonlinear frequency shift of finite-amplitude electrostatic surface waves  

International Nuclear Information System (INIS)

The problem concerning the appropriate form for the nonlinear frequency shift arising from slow density modulations of electrostatic surface waves in a semi-infinite unmagnetized plasma is reconsidered. The spatial dependence of the wave amplitude normal to the surface is kept general in order to allow for possible nonlinear attenuation behaviour of the surface waves. It is found that if the frequency shift is expressed as a function of the density and its gradient then the result is identical with that of Zhelyazkov, I. Proceedings International Conference on Plasma Physics, Kiev, 1987, Vol. 2, p. 694, who assumed a linear exponential attenuation behaviour. (author)

316

Nonlinear frequency shift of finite-amplitude electrostatic surface waves  

Energy Technology Data Exchange (ETDEWEB)

The problem concerning the appropriate form for the nonlinear frequency shift arising from slow density modulations of electrostatic surface waves in a semi-infinite unmagnetized plasma is reconsidered. The spatial dependence of the wave amplitude normal to the surface is kept general in order to allow for possible nonlinear attenuation behaviour of the surface waves. It is found that if the frequency shift is expressed as a function of the density and its gradient then the result is identical with that of Zhelyazkov, I. Proceedings International Conference on Plasma Physics, Kiev, 1987, Vol. 2, p. 694, who assumed a linear exponential attenuation behaviour. (author).

Stenflo, L. (Umeaa Univ. (Sweden). Dept. of Theoretical Plasma Physics); Yu, M.Y. (Bochum Univ. (Germany, F.R.))

1989-04-01

317

On analytical properties of multiple production amplitudes  

International Nuclear Information System (INIS)

Local analytical properties of amplitudes 2?3 and 2?4 are studied. The amplitudes are shown to be analytical functions of total and partial energies at fixed momentum transfers in the neighbourhood of any physical point on the energy shell 14 (for the 2?3 case) and 242 (for the 2?4 case) boundary values are expressed through the amplitudes of real processes

318

Minimal Basis for Gauge Theory Amplitudes  

CERN Document Server

Identities based on monodromy for integrations in string theory are used to derive relations between different color ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)! amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.

Bjerrum-Bohr, N E J; Vanhove, Pierre

2009-01-01

319

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

Directory of Open Access Journals (Sweden)

Full Text Available In task-switching paradigms, performance is better when repeating the same task than when alternating between tasks (switch cost and when repeating a task alone rather than intermixed with another task (mixing cost. These costs remain even after extensive practice and when task cues enable advanced preparation (residual costs. Moreover, residual RT mixing cost has been consistently shown to increase with age. Residual switch and mixing costs modulate the amplitude of the stimulus-locked P3b. This mixing effect is disproportionately larger in older adults who also prepare more for and respond more cautiously on these ‘mixed’ repeat trials (Karayanidis et al., 2011. In this study, we examine stimulus-locked and response-locked P3 and lateralized readiness potentials to identify whether residual switch and mixing cost arise from the need to control interference at the level of stimulus processing or response processing. Residual mixing cost was associated with control of stimulus-level interference, whereas residual switch cost was also associated with a delay in response selection. In older adults, the disproportionate increase in mixing cost was associated with greater interference at the level of decision-response mapping and response programming for repeat trials in mixed-task blocks. We argue that, together with evidence of greater proactive control and more cautious responding for these trials, these findings suggest that older adults strategically recruit greater proactive and reactive control to overcome increased susceptibility to post-stimulus interference. This interpretation is consistent with recruitment of compensatory strategies to compensate for reduced repetition benefit rather than an overall decline on cognitive flexibility.

FriniKarayanidis

2014-04-01

320

Investigation of the maximum amplitude increase from the Benjamin-Feir instability  

CERN Document Server

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.

Karjanto, N; Peterson, P

2011-01-01

 
 
 
 
321

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

CERN Document Server

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

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

2006-01-01

322

DVCS amplitude with kinematical twist-3 terms  

CERN Document Server

We compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude we include the operators of twist-3 which appear as total derivatives of twist-2 operators. Our results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. We find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.

Radyushkin, A V

2000-01-01

323

Amplitude structure of off-shell processes  

Energy Technology Data Exchange (ETDEWEB)

The structure of M matrices, or scattering amplitudes, and of potentials for off-shell processes is discussed with the objective of determining how one can obtain information on off-shell amplitudes of a process in terms of the physical observables of a larger process in which the first process is embedded. The procedure found is inevitably model dependent, but within a particular model for embedding, a determination of the physically measurable amplitudes of the larger process is able to yield a determination of the off-shell amplitudes of the embedded process.

Fearing, H.W.; Goldstein, G.R.; Moravcsik, M.J.

1984-06-01

324

Intrinsic-Normal-Ordered Vertex Operators from the Multiloop N-Tachyon Amplitude.  

Science.gov (United States)

We construct vertex operators for arbitrary mass level states of the closed bosonic string. Starting from a generalization of the Koba-Nielsen amplitude which is suitable for an arbitrary genus Riemann surface, we read the vertex operators from the residu...

G. Aldazabal, C. Nunez, M. Bonini, R. Iengo

1987-01-01

325

Secondary threshold amplitudes for sinuous streak breakdown  

Science.gov (United States)

The nonlinear stability of laminar sinuously bent streaks is studied for the plane Couette flow at Re = 500 in a nearly minimal box and for the Blasius boundary layer at Re?*=700. The initial perturbations are nonlinearly saturated streamwise streaks of amplitude AU perturbed with sinuous perturbations of amplitude AW. The local boundary of the basin of attraction of the linearly stable laminar flow is computed by bisection and projected in the AU - AW plane providing a well defined critical curve. Different streak transition scenarios are seen to correspond to different regions of the critical curve. The modal instability of the streaks is responsible for transition for AU = 25%-27% for the considered flows, where sinuous perturbations of amplitude below AW ? 1%-2% are sufficient to counteract the streak viscous dissipation and induce breakdown. The critical amplitude of the sinuous perturbations increases when the streamwise streak amplitude is decreased. With secondary perturbations amplitude AW ? 4%, breakdown is induced on stable streamwise streaks with AU ? 13%, following the secondary transient growth scenario first examined by Schoppa and Hussain [J. Fluid Mech. 453, 57 (2002)]. A cross-over, where the critical amplitude of the sinuous perturbation becomes larger than the amplitude of streamwise streaks, is observed for streaks of small amplitude AU < 5%-6%. In this case, the transition is induced by an initial transient amplification of streamwise vortices, forced by the decaying sinuous mode. This is followed by the growth of the streaks and final breakdown. The shape of the critical AU - AW curve is very similar for Couette and boundary layer flows and seems to be relatively insensitive to the nature of the edge states on the basin boundary. The shape of this critical curve indicates that the stability of streamwise streaks should always be assessed in terms of both the streak amplitude and the amplitude of spanwise velocity perturbations.

Cossu, Carlo; Brandt, Luca; Bagheri, Shervin; Henningson, Dan S.

2011-07-01

326

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

International Nuclear Information System (INIS)

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

327

BCFW construction of the Veneziano amplitude  

Energy Technology Data Exchange (ETDEWEB)

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

Fotopoulos, Angelos, E-mail: foto@to.infn.it [Dipartimento di Fisica Teorica dell Universita di Torino and INFN Sezione di Torino, via P. Giuria 1, I-10125 Torino (Italy)

2011-06-10

328

?- and K-meson Bethe-Salpeter amplitudes  

International Nuclear Information System (INIS)

Independent of assumptions about the form of the quark-quark scattering kernel K, we derive the explicit relation between the flavor-nonsinglet pseudoscalar-meson Bethe-Salpeter amplitude ?H and the dressed-quark propagator in the chiral limit. In addition to a term proportional to ?5, ?H necessarily contains qualitatively and quantitatively important terms proportional to ?5?·P and ?5?·kk·P, where P is the total momentum of the bound state. The axial-vector vertex contains a bound state pole described by ?H, whose residue is the leptonic decay constant for the bound state. The pseudoscalar vertex also contains such a bound state pole and, in the chiral limit, the residue of this pole is related to the vacuum quark condensate. The axial-vector Ward-Takahashi identity relates these pole residues, with the Gell-Mann endash Oakes endash Renner relation a corollary of this identity. The dominant ultraviolet asymptotic behavior of the scalar functions in the meson Bethe-Salpeter amplitude is fully determined by the behavior of the chiral limit quark mass function, and is characteristic of the QCD renormalization group. The rainbow-ladder Ansatz for K, with a simple model for the dressed-quark-quark interaction, is used to illustrate and elucidate these general results. The model preserves the one-loop renormalization group structure of QCD. The numerical studies also provide a means of exploring procedures for solving the Bethe-Salpeter equation without a three-dimensional reduction. copyright 1997 The American Physical Society

329

New relations for gauge-theory amplitudes  

International Nuclear Information System (INIS)

We present an identity satisfied by the kinematic factors of diagrams describing the tree amplitudes of massless gauge theories. This identity is a kinematic analog of the Jacobi identity for color factors. Using this we find new relations between color-ordered partial amplitudes. We discuss applications to multiloop calculations via the unitarity method. In particular, we illustrate the relations between different contributions to a two-loop four-point QCD amplitude. We also use this identity to reorganize gravity tree amplitudes diagram by diagram, offering new insight into the structure of the Kawai-Lewellen-Tye (KLT) relations between gauge and gravity tree amplitudes. This insight leads to similar but novel relations. We expect this to be helpful in higher-loop studies of the ultraviolet properties of gravity theories.

330

Magnetospheric chorus - Amplitude and growth rate  

Science.gov (United States)

A new study of the amplitude of magnetospheric chorus with 1966-1967 data from the Stanford University/Stanford Research Institute VLF receivers on Ogo 1 and Ogo 3 has confirmed the band-limited character of magnetospheric chorus in general and the double-banding of near-equatorial chorus. Chorus amplitude tended to be inversely correlated with frequency, implying lower intensities at lower L values. Individual chorus emissions often showed a characteristic amplitude variation, with rise times of 10 to 300 ms, a short duration at peak amplitude, and decay times of 100 to 3000 msec. Growth was often approximately exponential, with rates from 200 to nearly 2000 dB/sec. Rate of change of frequency was found in many cases to be independent of emission amplitude, in agreement with the cyclotron feedback theory of chorus (Helliwell, 1967, 1970).

Burtis, W. J.; Helliwell, R. A.

1975-01-01

331

Modulation compression for short wavelength harmonic generation  

International Nuclear Information System (INIS)

Laser modulator is used to seed free electron lasers. In this paper, we propose a scheme to compress the initial laser modulation in the longitudinal phase space by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C, where C is the compression factor of the first bunch compressor. Such a compressed energy modulation can be directly used to generate short wavelength current modulation with a large bunching factor.

332

Effect of Modulation Error on All Optical Fiber Current Transformers  

Directory of Open Access Journals (Sweden)

Full Text Available 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 voltage variation could affect the output accuracies significantly. This might be some references on the investigation for practical applications of AOFCTs.

Zhengping Wang

2012-12-01

333

Amplitude-dependent internal friction in high purity molybdenum; single crystals in the temperature range 5.9 - 300 K  

International Nuclear Information System (INIS)

Amplitude and temperature dependences of internal friction in molybdenum single crystals of the orientations , , , are studied. The residual resistance ratio of the samples is (1-2)x105. The measurements are carried out at the frequency of 88 kHz in the temperature range 5.9 - 300 K. It has been established that at high temperatures the amplitude-dependent internal friction is due to the process of thermally activated dislocation unpinning from the pinning centres. At low temperatures a maximum is found in the amplitude dependences the height of which decreases with decreasing temperature, but its position does not depend on the temperature. In the same amplitude range a saturation region appears in the modulus defect amplitude dependences. Such a behaviour of the high-amplitude internal friction at low temperatures can not be explained in the framework of the theories present

334

Attitude Maneuvers of CTS-like Spacecraft Using PD based Constant-Amplitude Inputs  

Directory of Open Access Journals (Sweden)

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.

Edward Halawa

2012-01-01

335

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

336

Understanding and Ameliorating Non-Linear Phase and Amplitude Responses in AMCW Lidar  

Directory of Open Access Journals (Sweden)

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.

John P. Godbaz

2011-12-01

337

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

CERN Document Server

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

Szabados, László

2011-01-01

338

Regge amplitudes with crossing and unitarity  

International Nuclear Information System (INIS)

A new crossing symmetric. Sommerfeld-Watson transformation is reported that produces an amplitude which moreover has the expected Regge asymptotic behaviour and the correct support of the Mandelstam double spectral functions

339

Open String Amplitudes in Various Gauges  

CERN Document Server

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.

Fuji, H; Suzuki, H; Fuji, Hiroyuki; Nakayama, Shinsaku; Suzuki, Hisao

2007-01-01

340

Analytic continuation of dual Feynman amplitudes  

International Nuclear Information System (INIS)

A notion of dual Feynman amplitude is introduced and a theorem on the existence of analytic continuation of this amplitude from the convergence domain to the whole complex is proved. The case under consideration corresponds to massless power propagators and the analytic continuation is constructed on the propagators powers. Analytic continuation poles and singular set of external impulses are found explicitly. The proof of the theorem on the existence of analytic continuation is based on the introduction of ?-representation for dual Feynman amplitudes. In proving, the so-called ''trees formula'' and ''trees-with-cycles formula'' are established that are dual by formulation to the trees and 2-trees formulae for usual Feynman amplitudes. (Auth.)

 
 
 
 
341

MHV-Vertices for Gravity Amplitudes  

CERN Document Server

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.

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

342

Transition amplitudes within the stochastic quantization scheme  

International Nuclear Information System (INIS)

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

343

Scattering amplitude for a screened Coulomb potential  

Energy Technology Data Exchange (ETDEWEB)

The scattering amplitude for an exponentially screened Coulomb potential is calculated exactly. The Born approximation is shown to differ sensibly from the exact result near O/sup 0/. Some physical consequences of this fact are discussed.

Bendiscioli, G.; Lodi Rizzini, E.; Rotondi, A.; Venaglioni, A. (Pavia Univ. (Italy). Ist. di Fisica Nucleare)

1981-05-23

344

Amplitude distribution of eigenfunctions in mixed systems  

International Nuclear Information System (INIS)

We study the amplitude distribution of irregular eigenfunctions in systems with mixed classical phase space. For an appropriately restricted random wave model, a theoretical prediction for the amplitude distribution is derived and a good agreement with numerical computations for the family of limacon billiards is found. The natural extension of our result to more general systems, e.g. with a potential, is also discussed. (author)

345

Transmission amplitudes from Bethe ansatz equations  

CERN Document Server

We consider the Heisenberg spin chain in the presence of integrable spin defects. Using the Bethe ansatz methodology, we extract the associated transmission amplitudes, that describe the interaction between the particle-like excitations displayed by the models and the spin impurity. In the attractive regime of the XXZ model, we also derive the breather's transmission amplitude. We compare our findings with earlier relevant results in the context of the sine-Gordon model.

Doikou, Anastasia

2012-01-01

346

Heterotic Approach to the Nucleon Distribution Amplitude  

CERN Document Server

We give an in-depth analysis of the determination procedure of the recently proposed heterotic nucleon distribution amplitude which hybridizes the best features of the Chernyak-Ogloblin-Zhitnitsky and the Gari-Stefanis models. With respect to the QCD sum-rule constraints, optimized versions of these amplitudes are derived in terms of which a "hybridity" angle can be introduced to systematically classify all models.

Bergmann, M J

1994-01-01

347

The neutron scattering amplitude of uranium  

International Nuclear Information System (INIS)

Reanalysis of six different sets of neutron diffraction data for UO2 leads to a value of the neutron scattering amplitude ratio of bsub(u)/b0 = 1.451(2) and hence a value for the neutron scattering amplitude of uranium of bsub(u) = 0.842(2) x 10-12 cm (assuming b0 = 0.5805(11) x 10-12 cm). (author)

348

Effective gluon interactions from superstring disk amplitudes  

Energy Technology Data Exchange (ETDEWEB)

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)

Oprisa, D.

2006-05-15

349

Computation of one-loop gluon amplitudes  

International Nuclear Information System (INIS)

A numerical approach for the computation of QCD one-loop gluon amplitudes in pure gauge theory is presented. Using generalized unitarity, we compute the coefficients of the occuring scalar one-loop integrals. As basic ingredient, the Berends-Giele recursion is used to construct on-shell tree amplitudes. The performance of the program is explored and the algorithms of the implemented methods are explained.

350

Nucleon distribution amplitudes from lattice QCD  

CERN Document Server

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 MSbar 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.

Göckeler, Meinulf; Kaltenbrunner, Thomas; Nakamura, Yoshifumi; Pleiter, Dirk; Rakow, Paul E L; Schäfer, Andreas; Schierholz, Gerrit; Stüben, Hinnerk; Warkentin, Nikolaus; Zanotti, James M

2008-01-01

351

Nucleon distribution amplitudes from lattice QCD  

International Nuclear Information System (INIS)

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.)

352

Color-flow decomposition of QCD amplitudes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We introduce a new color decomposition for multi-parton amplitudes in QCD, free of fundamental-representation matrices and structure constants. This decomposition has a physical interpretation in terms of the flow of color, which makes it ideal for merging with shower Monte-Carlo programs. The color-flow decomposition allows for very efficient evaluation of amplitudes with many quarks and gluons, many times faster than the standard color decomposition based on fundamental-re...

Maltoni, F.; Paul, K.; Stelzer, T.; Willenbrock, S.

2002-01-01

353

AMPLITUDE DEPENDENCE OF TIME OF FLIGHT  

International Nuclear Information System (INIS)

Machida found in tracking studies [Shinji Machida, presentation at the FFAG05 Workshop, Kyoto University Research Reactor Institute, Osaka, Japan, 5-9 December 2005] that the time of flight in a linear non-scaling FFAG depended on the transverse amplitude of the particles. I compute a relationship between the transverse amplitude dependence of the time of flight and the variation of tune with energy and explain its physical origin

354

Waveform Sampler CAMAC Module  

Energy Technology Data Exchange (ETDEWEB)

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 ..mu..s conversion time and stored in an on-board memory accessible through CAMAC.

Freytag, D.R.; Haller, G.M.; Kang, H.; Wang, J.

1985-09-01

355

Waveform Sampler CAMAC Module  

International Nuclear Information System (INIS)

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

356

Waveform sampler CAMAC module  

International Nuclear Information System (INIS)

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

357

Online tracking of instantaneous frequency and amplitude of dynamical system response  

Science.gov (United States)

This paper presents a sliding-window tracking (SWT) method for accurate tracking of the instantaneous frequency and amplitude of arbitrary dynamic response by processing only three (or more) most recent data points. Teager-Kaiser algorithm (TKA) is a well-known four-point method for online tracking of frequency and amplitude. Because finite difference is used in TKA, its accuracy is easily destroyed by measurement and/or signal-processing noise. Moreover, because TKA assumes the processed signal to be a pure harmonic, any moving average in the signal can destroy the accuracy of TKA. On the other hand, because SWT uses a constant and a pair of windowed regular harmonics to fit the data and estimate the instantaneous frequency and amplitude, the influence of any moving average is eliminated. Moreover, noise filtering is an implicit capability of SWT when more than three data points are used, and this capability increases with the number of processed data points. To compare the accuracy of SWT and TKA, Hilbert-Huang transform is used to extract accurate time-varying frequencies and amplitudes by processing the whole data set without assuming the signal to be harmonic. Frequency and amplitude trackings of different amplitude- and frequency-modulated signals, vibrato in music, and nonlinear stationary and non-stationary dynamic signals are studied. Results show that SWT is more accurate, robust, and versatile than TKA for online tracking of frequency and amplitude.

Frank Pai, P.

2010-05-01

358

Amplitude regeneration of RZ-DPSK signals in single-pump fiber-optic parametric amplifiers  

DEFF Research Database (Denmark)

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.

Peucheret, Christophe; Lorenzen, Michael Rodas

2009-01-01

359

Learning Modules for an Electronics Curriculum  

Science.gov (United States)

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

2009-08-14

360

Vector Modulator for Phase Shifting in Passive Beamforming Wireless Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes vector modulator for changing the phase of a signal in passive beamforming system. Vector modulator is used to perform a phase shift function with added benefit of amplitude control. It is used to improve the directivity of RF waves in Wireless systems. Vector modulator is implemented for a center frequency of 902.5 MHz. The simulation is performed for individual blocks of the vector modulator and for vector modulator with JFET and MOSFET as controlling device in the varia...

P.Sampath,; Gunavathi, K.

2010-01-01

 
 
 
 
361

Regge analysis of the {pi}{pi} scattering amplitude  

Energy Technology Data Exchange (ETDEWEB)

The theoretical predictions for the subtraction constants lead to a very accurate dispersive representation of the {pi}{pi} scattering amplitude below 0.8 GeV. The extension of this representation up to the maximum energy of validity of the Roy equations (1.15 GeV) requires a more precise input at high energies. In this paper we determine the trajectories and residues of the leading Regge contributions to the {pi}{pi} amplitude (Pomeron, f and {rho}), using factorization, phenomenological parametrizations of the {pi}N and NN total cross sections at high energy, and a set of sum rules which connect the high and low energy properties of {pi}{pi} scattering. We find that nonleading Regge terms are necessary in order to achieve a smooth transition from the partial waves to the Regge representation at or below 2 GeV. We obtain thus a Regge representation consistent both with the experimental information at high energies and the Roy equations for the partial waves with l{<=}4. The uncertainties in our result for the Regge parameters are sizable, but in the solutions of the Roy equations these only manifest themselves above the K anti K threshold. (orig.)

Caprini, I. [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, Magurele (Romania); Colangelo, G.; Leutwyler, H. [University of Bern, Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Bern (Switzerland)

2012-02-15

362

RESIDUATED WEAK LATTICES  

Directory of Open Access Journals (Sweden)

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

M. BASHEER AHAMED

2010-12-01

363

Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly  

CERN Document Server

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.

Nikolov, Nikolay M; Todorov, Ivan

2013-01-01

364

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.

365

Modulation techniques  

Science.gov (United States)

Bandwidth efficient digital modulation techniques, proposed for use on and/or applied to satellite channels, are reviewed. In a survey of recent works on digital modulation techniques, the performance of several schemes operating in various environments are compared. Topics covered include: (1) quadrature phase shift keying; (2) offset - QPSK and MSK; (3) combined modulation and coding; and (4) spectrally efficient modulation techniques.

Schilling, D. L.

1982-01-01

366

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

367

On Arbitrary Phases in Quantum Amplitude Amplification  

CERN Document Server

We consider the use of arbitrary phases in quantum amplitude amplification which is a generalization of quantum searching. We prove that the phase condition in amplitude amplification is given by $\\tan(\\phi/2)=\\tan(\\phi/2)(1-2a)$, where $\\phi$ and $\\phi$ are the phases used and where $a$ is the success probability of the given algorithm. Thus the choice of phases depends nontrivially and nonlinearly on the success probability. Utilizing this condition, we give methods for constructing quantum algorithms that succeed with certainty and for implementing arbitrary rotations. We also conclude that phase errors of order up to $\\frac{1}{\\sqrt{a}}$ can be tolerated in amplitude amplification.

Hoyer, P

2000-01-01

368

Spectral Amplitude Coding (SAC)-OCDMA Network with 8DPSK  

Science.gov (United States)

Optical code division multiple access (OCDMA) technique is required to meet the increased demand for high speed, large capacity communications in optical networks. In this paper, the transmission performance of a spectral amplitude coding (SAC)-OCDMA network is investigated when a conventional single-mode fiber (SMF) is used as the transmission link using 8DPSK modulation. The DW has a fixed weight of two. Simulation results reveal that the transmission distance is limited mainly by the fiber dispersion when high coding chip rate is used. For a two-user SAC-OCDMA network operating with 2 Gbit/s data rate and two wavelengths for each user, the maximum allowable transmission distance is about 15 km.

Aldhaibani, A. O.; Aljunid, S. A.; Fadhil, Hilal A.; Anuar, M. S.

2013-09-01

369

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)

370

Elastic Amplitudes and Observables in pp Scattering  

CERN Document Server

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.

Ferreira, Erasmo; Kohara, Anderson Kendi

2014-01-01

371

High energy multi-gluon exchange amplitudes  

International Nuclear Information System (INIS)

We examine perturbative high energy n-gluon exchange amplitudes calculated in the Coulomb gauge. If n exceeds the minimum required by the t-channel quantum numbers, such amplitudes are non-leading in lns. We derive a closed system of coupled integral equations for the corresponding two-particle n-gluon vertices, obtained by summing the leading powers of ln(N ? psup(?)), where psup(?) is the incident momentum and Nsup(?) the gauge-defining vector. Our equations are infra-red finite, provided the external particles are colour singlets. (author)

372

Massive QCD amplitudes at higher orders  

International Nuclear Information System (INIS)

We consider the factorization properties of on-shell QCD amplitudes with massive partons in the limit when all kinematical invariants are large compared to the parton mass and discuss the structure of their infrared singularities. The dimensionally regulated soft poles and the large collinear logarithms of the parton masses exponentiate to all orders. Based on this factorization a simple relation between massless and massive scattering amplitudes in gauge theories can be established. We present recent applications of this relation for the calculation of the two-loop virtual QCD corrections to the hadro-production of heavy quarks. (orig.)

373

String scattering amplitudes from Dyson gas  

Energy Technology Data Exchange (ETDEWEB)

In this note we review the relation between the open string rolling tachyon background and a classical two-dimensional Coulomb gas on a circle - the Dyson gas. Open string n-point amplitudes directly relate to adding external charges on the Dyson gas ensemble. By calculating the grand canonical partition function of the Dyson with external charges we find an approximation formula for the string amplitude. This note is based on the work with M. Jaervinen and Esko Keski-Vakkuri, eprint (arXiv:0806.1491).

Jokela, Niko [Helsinki Institute of Physics and Department of Physics, P.O. Box 64, FIN-00014 University of Helsinki (Finland); Department of Physics, Technion, Haifa 32000 (Israel); Department of Mathematics and Physics, University of Haifa at Oranim, Tivon 36006 (Israel)

2009-07-15

374

String scattering amplitudes from Dyson gas  

International Nuclear Information System (INIS)

In this note we review the relation between the open string rolling tachyon background and a classical two-dimensional Coulomb gas on a circle - the Dyson gas. Open string n-point amplitudes directly relate to adding external charges on the Dyson gas ensemble. By calculating the grand canonical partition function of the Dyson with external charges we find an approximation formula for the string amplitude. This note is based on the work with M. Jaervinen and Esko Keski-Vakkuri, eprint (arXiv:0806.1491).

375

Residual stress reduction and fatigue strength improvement by controlling welding pass sequences  

Energy Technology Data Exchange (ETDEWEB)

The effects of residual stress on fatigue strength at a weld toe in a multi-pass fillet weld joint were evaluated. The residual stresses in the weld joints were varied by controlling the sequence of welding passes. The residual stress at the weld toe was 80 MPa in the specimen whose last welding pass was on the main plate side, but it was 170 MPa in the specimen whose last pass was on the attachment side. The fatigue strength was nearly the same at high stress amplitude for both specimens, but the fatigue strength of the specimen whose last weld pass on the main plate was higher than that of the other specimen at low stress amplitude. This difference is due to the magnitude of the initial residual stress and the relaxation of the residual stress under fatigue cycling. The effects of the residual stress were shown in a modified Goodman diagram, in which residual stress is treated as a mean stress.

Mochizuki, Masahito; Hattori, Toshio; Nakakado, Kimiaki

2000-01-01

376

Abelian modules  

Directory of Open Access Journals (Sweden)

Full Text Available In this note, we introduce abelian modules as a generalization of abelian rings. Let R be an arbitrary ring with identity. A module M is called abelian if, for any m Î M and any a Î R, any idempotent e Î R, mae=mea. We prove that every reduced module, every symmetric module, every semicommutative module and every Armendariz module is abelian. For an abelian ring R, we show that the module MR is abelian iff M[x]R[x] is abelian. We produce an example to show that M[x, ?] need not be abelian for an abelian module M and an endomorphism ? of the ring R. We also prove that if the module M is abelian, then M is p.p.-module iff M[x] is p.p.-module, M is Baer module iff M[x] is Baer module, M is p.q.-Baer module iff M[x] is p.q.-Baer module.

S. Hal?c?o?lu

2009-08-01

377

Spatial Terahertz Modulator  

Science.gov (United States)

Terahertz (THz) technology is a developing and promising candidate for biological imaging, security inspection and communications, due to the low photon energy, the high transparency and the broad band properties of the THz radiation. However, a major encountered bottleneck is lack of efficient devices to manipulate the THz wave, especially to modulate the THz wave front. A wave front modulator should allow the optical or electrical control of the spatial transmission (or reflection) of an input THz wave and hence the ability to encode the information in a wave front. Here we propose a spatial THz modulator (STM) to dynamically control the THz wave front with photo-generated carriers. A computer generated THz hologram is projected onto a silicon wafer by a conventional spatial light modulator (SLM). The corresponding photo-generated carrier spatial distribution will be induced, which forms an amplitude hologram to modulate the wave front of the input THz beam. Some special intensity patterns and vortex beams are generated by using this method. This all-optical controllable STM is structure free, high resolution and broadband. It is expected to be widely used in future THz imaging and communication systems.

Xie, Zhenwei; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Akalin, Tahsin; Zhang, Yan

2013-11-01

378

Attenuation of ground-motion spectral amplitudes in southeastern Australia  

Science.gov (United States)

A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for southeastern Australia (SEA). Events were recorded from 1993 to 2004 and range in size from moment magnitude 2.0 ??? M ??? 4.7. The decay of vertical-component Fourier spectral amplitudes is modeled by trilinear geometrical spreading. The decay of low-frequency spectral amplitudes can be approximated by the coefficient of R-1.3 (where R is hypocentral distance) within 90 km of the seismic source. From approximately 90 to 160 km, we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and Moho discontinuities. In this hypocentral distance range, geometrical spreading is approximately R+0.1. Beyond 160 km, low-frequency seismic energy attenuates rapidly with source-receiver distance, having a geometrical spreading coefficient of R-1.6. The associated regional seismic-quality factor can be expressed by the polynomial: log Q(f) = 3.66 - 1.44 log f + 0.768 (log f)2 + 0.058 (log f)3 for frequencies 0.78 ??? f ??? 19.9 Hz. Fourier spectral amplitudes, corrected for geometrical spreading and anelastic attenuation, are regressed with M to obtain quadratic source scaling coefficients. Modeled vertical-component displacement spectra fit the observed data well. Amplitude residuals are, on average, relatively small and do not vary with hypocentral distance. Predicted source spectra (i.e., at R = 1 km) are consistent with eastern North American (ENA) Models at low frequencies (f less than approximately 2 Hz) indicating that moment magnitudes calculated for SEA earthquakes are consistent with moment magnitude scales used in ENA over the observed magnitude range. The models presented represent the first spectral ground-motion prediction equations develooed for the southeastern Australian region. This work provides a useful framework for the development of regional ground-motion relations for earthquake hazard and risk assessment in SEA.

Allen, T.I.; Cummins, P.R.; Dhu, T.; Schneider, J.F.

2007-01-01

379

Development of an electro-optic super modulator  

International Nuclear Information System (INIS)

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

380

Intrinsic normal-ordered vertex operators from the multiloop N-tachyon amplitude  

Energy Technology Data Exchange (ETDEWEB)

We construct vertex operators for arbitrary mass level states of the closed bosonic string. Starting from a generalization of the Koba-Nielsen amplitude which is suitable for an arbitrary genus Riemann surface, we read the vertex operators from the residues of the poles for the intermediate states. Since the original expression is metric independent and normal ordered without the need of inventing any regularization scheme, our vertex operators also possess these properties. We discuss their general features.

Aldazabal, G.; Bononi, M.; Iengo, R.; Nunez, C.

1987-12-10

 
 
 
 
381

Intrinsic-normal-ordered vertex operators from the multiloop N-tachyon amplitude  

International Nuclear Information System (INIS)

We construct vertex operators for arbitrary mass level states of the closed bosonic string. Starting from a generalization of the Koba-Nielsen amplitude which is suitable for an arbitrary genus Riemann surface, we read the vertex operators from the residues of the poles for the intermediate states. Since the original expression is metric independent and normal ordered without the need of inventing any regularization scheme, our vertex operators also possess these properties. We discuss their general features. (author). 17 refs

382

Grassmannians for scattering amplitudes in 4d $\\mathcal{N}=4$ SYM and 3d ABJM  

CERN Document Server

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.

Elvang, Henriette; Keeler, Cynthia; Lam, Thomas; Olson, Timothy M; Roland, Samuel B; Speyer, David E

2014-01-01

383

Particle distribution modification by low amplitude modes  

International Nuclear Information System (INIS)

Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven eigenmodes and reversed shear Alfven eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

384

The pion-pion scattering amplitude  

CERN Document Server

We obtain reliable $\\pi\\pi$ scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy ($s^{1/2}\\leq1.42 {\\rm GeV}$) phase shifts and inelasticities with expressions that incorporate analyticity and unitarity. In particular, for the S wave with isospin~0, we discuss in detail several sets of experimental data. This provides low energy partial wave amplitudes that summarize the known experimental information. Then, we impose Regge behaviour as follows from factorization and experimental data for the imaginary parts of the scattering amplitudes at higher energy, and check fulfillment of dispersion relations up to 0.925 GeV. This allows us to improve our fits. The ensuing $\\pi\\pi$ scattering amplitudes are then shown to verify dispersion relations up to 1.42 GeV, as well as $s - t - u$ crossing sum rules and other consistency conditions. The improved parametrizations therefore provi...

Peláez, J R

2004-01-01

385

Particle Distribution Modification by Low Amplitude Modes  

International Nuclear Information System (INIS)

Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

386

Amplitude Frequency Response Measurement: A Simple Technique  

Science.gov (United States)

A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

Satish, L.; Vora, S. C.

2010-01-01

387

Periods, amplitudes, and luminosities of red supergiants  

International Nuclear Information System (INIS)

The periods of 22 red supergiants have been determined using the results of electrophotometric observations. The period-luminosity-spectrum and amplitude-luminosity-spectrum dependences for the red supergiants have been obtained. The masses and luminosities of these stars are estimated

388

Kaon decay amplitudes using staggered fermions  

Energy Technology Data Exchange (ETDEWEB)

A status report is given of an attempt, using staggered fermions to calculate the real and imaginary parts of the amplitudes for K ..-->.. ..pi pi..,. Semi-quantitative results are found for the imaginary parts, and these suggest that epsilon' might be smaller than previously expected in the standard model.

Sharpe, S.R.

1986-12-01

389

Kaon decay amplitudes using staggered fermions  

International Nuclear Information System (INIS)

A status report is given of an attempt, using staggered fermions to calculate the real and imaginary parts of the amplitudes for K ? ??,. Semi-quantitative results are found for the imaginary parts, and these suggest that ?' might be smaller than previously expected in the standard model

390

Calculating real Delbrueck amplitudes on parallel processors  

International Nuclear Information System (INIS)

Calculation of the real Delbrueck scattering amplitudes is parallelized by concurrent evaluation of 20 four-dimensional integrals. Two approaches were used: (a) a farm of master and workers tasks, and (b) the Cubix concept of parallelization. We discuss load balancing, timing and the efficiency of the implementation. (orig.)

391

Amplitude squeezed fiber Bragg grating solitons  

CERN Document Server

Quantum fluctuations of optical fiber Bragg grating solitons are investigated numerically by the back-propagation method. It is found for the first time that the bandgap effects of the grating act as a nonlinear filter and cause the soliton to be amplitude squeezed. The squeezing ratio saturates after a certain grating length and the fundamental Bragg soliton produces the optimal squeezing ratio.

Lee, R K; Lee, Ray-Kuang; Lai, Yinchieh

2004-01-01

392

Particle Distribution Modification by Low Amplitude Modes  

Energy Technology Data Exchange (ETDEWEB)

Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

R.B. White, N. Gorelenkov, W.W. Heidbrink, and M.A. Van Zeeland

2009-08-28

393

Ward Identities for Amplitudes with Reggeized Gluons  

CERN Document Server

Starting from the effective action of high energy QCD we derive Ward identities for Green's functions of reggeized gluons. They follow from the gauge invariance of the effective action, and allow to derive new representations of amplitudes containing physical particles as well as reggeized gluons. We explicitly demonstrate their validity for the BFKL kernel, and we present a new derivation of the kernel.

Bartels, J; Vacca, G P

2012-01-01

394

Yield Estimation from Surface-wave Amplitudes  

Science.gov (United States)

Surface-wave amplitudes from explosion sources show less variation for a given event han body wave amplitudes, so it is natural to expect that yield estimates derived from surface waves will be more accurate than yield estimates derived from body waves. However, yield estimation from surface waves is complicated by the presence of tectonic strain release, which acts like one or more earthquake sources superimposed on top of the explosion. Moment-tensor inversion can be used to remove the tectonic component of the surface waves, however moment-tensor inversion for shallow sources is inherently non-unique so the explosion isotropic moment cannot be determined with the necessary accuracy by this means. Explosions on an island or near a mountain slope can exhibit anomalous surface waves similar to those caused by tectonic strain release. These complications cause yield estimates derived from surface waves to be less accurate than yield estimates from body waves recorded on a well-calibrated network with good coverage. Surface-wave amplitudes can be expressed as a surface-wave magnitude Ms, which is defined as the logarithm of the amplitude plus a distance correction, or as a path corrected spectral magnitude, log M'0, which is derived from the surface-wave spectrum. We derive relations for Ms vs. yield and log M'0 vs. yield for a large data set and estimate the accuracy of these estimates.

Stevens, J. L.; Murphy, J. R.

395

Modulation of whistlers  

Science.gov (United States)

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).

Sivokon', V. P.; Bogdanov, V. V.; Druzhin, G. I.; Cherneva, N. V.; Kubyshkin, A. V.; Sannikov, D. V.; Agranat, I. V.

2014-11-01

396

Investigation of the modulation between EEG alpha waves and slow/fast delta waves in children in different depths of Desflurane anesthesia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objectives: Investigation of the amplitude modulation of alpha-band EEG oscillations (i.e., grouping of alpha-band activities) by delta-band EEG activities in various depths of anesthesia (DOA). Methods: This modulation, which is a sort of phase dependent amplitude modulation, is studied in 10 children in various depths of Desflurane anesthesia. Two parameters are defined to quantify the modulation: strength of modulation (SOM) and phase of modulation (POM). SOM indicates to what extent delta...

Molaee-ardekani, Behnam; Shamsollahi, Mohammad Bagher; Tirel, Olivier; Vosoughi-vahdat, Bijan; Wodey, Eric; Senhadji, Lotfi

2010-01-01

397

Crack propagation under variable amplitude loading  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Experience shows that a damage induced by a given cycle is dependent on the loading history. In this regard, the objective of this paper is to study and describe the phenomenology of the loading history on crack propagation. Different loading configuration has been considered for fatigue crack propa [...] gation of XC38 steel; overload cycles followed by underload and vice versa were considered during propagation. Measure of crack opening has been made using compliance method. It is shown that the main parameters which cause retardation are the residual compressive stresses and the crack closure. The finite element modeling is used to calculate the evolution of residual stress profiles before and after application of the overload-underload cycle. It corroborates the hypotheses on the mechanisms behind, including those proposed on the residual stresses at the crack tip.

Miloudi, Abdelkader; Zemri, Mokhtar; Benguediab, Mohamed; Mazari, Mohamed; Amrouche, Abdelwaheb.

1161-11-01

398

Crack propagation under variable amplitude loading  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Experience shows that a damage induced by a given cycle is dependent on the loading history. In this regard, the objective of this paper is to study and describe the phenomenology of the loading history on crack propagation. Different loading configuration has been considered for fatigue crack propa [...] gation of XC38 steel; overload cycles followed by underload and vice versa were considered during propagation. Measure of crack opening has been made using compliance method. It is shown that the main parameters which cause retardation are the residual compressive stresses and the crack closure. The finite element modeling is used to calculate the evolution of residual stress profiles before and after application of the overload-underload cycle. It corroborates the hypotheses on the mechanisms behind, including those proposed on the residual stresses at the crack tip.

Miloudi, Abdelkader; Zemri, Mokhtar; Benguediab, Mohamed; Mazari, Mohamed; Amrouche, Abdelwaheb.

399

Modulational instability of obliquely modulated ion-acoustic waves in a two-electron-temperature plasma  

International Nuclear Information System (INIS)

The unstable domain in the (k,phi) plane for oblique modulation of ion-acoustic waves, in a two-electron-temparature plasma, is investigated using the KBM perturbation technique. It is shown that, in a collisionless plasma, the maximum growth rate for the modulational instability, for large carrier-wave amplitudes (a0 > or approx. 0.1), exceeds the electron Landau damping rate for sufficiently oblique modulation. (author)

400

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)

 
 
 
 
401

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

402

Transition amplitudes in de Sitter space  

Science.gov (United States)

Maldacena has shown that the wavefunction of the universe in de Sitter space can be viewed as the partition function of a conformal field theory. In this paper, we investigate this approach to the dS/CFT correspondence in further detail. We emphasize that massive bulk fields are dual to two primary operators on the boundary, which encode information about the two independent behaviors of bulk expectation values at late times. An operator statement of the duality is given, and it is shown that the resulting boundary correlators can be interpreted as transition amplitudes from the Bunch-Davies vacuum to an excited state in the infinite future. We also explain how these scattering amplitudes can be used to compute late-time Bunch-Davies expectation values, and comment on the effects of anomalies in the dual CFT on such expectation values.

Dodelson, Matthew

2012-08-01

403

Transition Amplitudes in de Sitter Space  

CERN Document Server

Maldacena has shown that the wavefunction of the universe in de Sitter space can be viewed as the partition function of a conformal field theory. In this paper, we investigate this approach to the dS/CFT correspondence in further detail. We emphasize that massive bulk fields are dual to two primary operators on the boundary, which encode information about the two independent behaviors of bulk expectation values at late times. An operator statement of the duality is given, and it is shown that the resulting boundary correlators can be interpreted as transition amplitudes from the Bunch-Davies vacuum to an excited state in the infinite future. We also explain how these scattering amplitudes can be used to compute late-time Bunch-Davies expectation values, and comment on the effects of anomalies in the dual CFT on such expectation values.

Dodelson, Matthew

2012-01-01

404

Planar scattering amplitudes from Wilson loops  

International Nuclear Information System (INIS)

We derive an expression for parton scattering amplitudes of planar gauge theory in terms of sums of Wilson loops. We study in detail the example of Yang-Mills theory with an adjoint Higgs field. The expression exhibits the T-duality performed by Alday and Maldacena in the AdS dual as a Fourier transform in loop space. When combined with the AdS/CFT correspondence for Wilson loops and a strong coupling argument for the dominance of 1PI diagrams, this leads to a derivation of the Alday-Maldacena holographic prescription for scattering amplitudes in terms of momentum Wilson loops. The formula leads to a conjecture for a relationship between position-space and momentum-space Wilson loops in N = 4 SYM at finite coupling.

405

Source amplitudes for active exterior cloaking  

Science.gov (United States)

The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the infinite region exterior to a set of circles defined by the relative positions of the sources. The results provide a direct solution to the inverse problem of determining the source amplitudes. They also define a broad class of non-radiating discrete sources.

Norris, Andrew N.; Amirkulova, Feruza A.; Parnell, William J.

2012-10-01

406

Limit on the pion distribution amplitude  

CERN Document Server

The pion distribution amplitude (DA) can be related to the fundamental QCD Green's functions as a function of the quark self-energy and the quark-pion vertex, which in turn are associated with the pion wave function through the Bethe-Salpeter equation. Considering the extreme hard asymptotic behavior in momentum space allowed for a pseudoscalar wave function, which is limited by its normalization condition, we compute the pion DA and its second moment. From the resulting amplitude, representing the field theoretical upper limit on the DA behavior, we calculate the photon-pion transition form factor $F_{\\pi\\gamma\\gamma^{\\ast}}(Q^{2})$. The resulting upper limit on the pion transition form factor is compared with existing data published by CLEO, BaBar and Belle collaborations.

Luna, E G S

2014-01-01

407

Automatic generation of quarkonium amplitudes in NRQCD  

International Nuclear Information System (INIS)

We present a simple method to automatically evaluate arbitrary tree-level amplitudes involving the production or decay of a heavy quark pair Q Q-bar in a generic 2S+1LJ[1,8], S- or P-wave state, i.e., the leading short distance coefficients appearing in the NRQCD factorization formalism. Our approach is based on extracting the relevant contributions from the open heavy quark-antiquark amplitudes through an expansion with respect to the quark-antiquark relative momentum and the application of suitable color and spin projectors. To illustrate the capabilities of the method and its implementation in MadGraph a few applications to quarkonium collider phenomenology are presented

408

Integrable spin chains and scattering amplitudes  

Energy Technology Data Exchange (ETDEWEB)

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.)

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

409

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)

410

Integrable spin chains and scattering amplitudes  

CERN Document Server

In this review we show that the multi-particle scattering amplitudes in N=4 SYM at large Nc and in the multi-Regge kinematics for some physical regions have the high energy behavior appearing from the contribution of the Mandelstam cuts in the complex angular momentum plane of the corresponding t-channel partial waves. These Mandelstam cuts or Regge cuts are resulting from gluon composite states in the adjoint representation of the gauge group SU(Nc). In the leading logarithmic approximation (LLA) their contribution to the six point amplitude is in full agreement with the known two-loop result. The Hamiltonian for the Mandelstam states constructed from n gluons in LLA coincides with the local Hamiltonian of an integrable open spin chain. We construct the corresponding wave functions using the integrals of motion and the Baxter-Sklyanin approach.

Bartels, J; Prygarin, A

2011-01-01

411

Scattering Equations and String Theory Amplitudes  

CERN Document Server

Scattering equations for tree-level amplitudes are viewed in the context of string theory. As a result of the comparison we are led to define a new dual model which coincides with string theory in both the small and large $\\alpha'$ limit, and whose solution is found algebraically on the surface of solutions to the scattering equations. Because it has support only on the scattering equations, it can be solved exactly, yielding a simple resummed model for $\\alpha'$-corrections to all orders. We use the same idea to generalize scattering equations to amplitudes with fermions and any mixture of scalars, gluons and fermions. In all cases checked we find exact agreement with known results.

Bjerrum-Bohr, N E J; Tourkine, P; Vanhove, P

2014-01-01

412

Source amplitudes for active exterior cloaking  

International Nuclear Information System (INIS)

The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the infinite region exterior to a set of circles defined by the relative positions of the sources. The results provide a direct solution to the inverse problem of determining the source amplitudes. They also define a broad class of non-radiating discrete sources. (paper)

413

Progress toward combined phase and amplitude demodulation fluorescence lifetime measurements by flow cytometry  

Science.gov (United States)

A phase-sensitive flow cytometer has been developed to quantify fluorescence lifetimes directly as a parameter in real time on particles and cells labeled with fluorophores. This instrument combines flow cytometry and frequency-domain fluorescence lifetime spectroscopy measurement principles to provide unique features for making excited-state lifetime measurements. Cells are analyzed as they intersect a high- frequency, intensity-modulated (sine wave) laser excitation beam. Fluorescence signals are processed by analog phase comparator measurement electronics to provide output signals proportional to the sine and cosine of the phase difference between the modulated signal input and a steady state reference signal. The ratios, which are proportional to the lifetimes, are displayed as frequency distributions histograms. In this study we present the underlying theory to measure fluorescence lifetimes by both phase shift and amplitude demodulation. Prototype analog amplitude demodulation electronics have been constructed and are being tested using simulated signals, fluorescent microspheres, and cells labeled with fluorescent probes.

Steinkamp, John A.; Parson, Jimmie D.; Keij, Jan F.

1998-04-01

414

A scattering matrix approach to quantum pumping: beyond the small-AC-driving-amplitude limit  

Science.gov (United States)

In the adiabatic and weak-modulation quantum pump, net electron flow is driven from one reservoir to another by absorbing or emitting an energy quantum ?? from or to the reservoirs. This paper considers high-order dependence of the scattering matrix on the time. Non-sinusoidal behaviour of strong pumping is revealed. The relation between the pumped current and the ac driving amplitude varies from power of 2, 1 to 1/2 when stronger modulation is exerted. Open experimental observation can be interpreted by multi-energy-quantum-related processes.

Zhu, Rui

2010-12-01

415

Automatic generation of tree level helicity amplitudes  

Science.gov (United States)

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.

Stelzer, T.; Long, W. F.

1994-11-01

416

Automatic generation of tree level helicity amplitudes  

CERN Document Server

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.

Stelzer, T

1994-01-01

417

Effective actions and topological string amplitudes  

International Nuclear Information System (INIS)

It is discussed how, in type II strings compactified on a Calabi-Yau manifold, the one-loop threshold corrections to gravitational couplings admit generalizations at an arbitrary loop order g, which connect ordinary string amplitudes to the topological string partition function Fg, obtained by twisting the internal N=2 theory. The recently studied holomorphic anomaly of Fg has then a natural interpretation in terms of non localities in the effective four dimensional field theory. (author). 11 refs

418

Squeezed vacuum from amplitude squeezed states.  

Science.gov (United States)

Squeezed vacuum permits adjustment of its relative phase to a chosen signal. If the signal is used as the probe in an interferometric measurement, the signal-to-noise ratio can be improved. We propose a system that generates squeezed vacuum, which consists of a laser diode that produces amplitude squeezed states and is phaselocked to a coherent signal, and an alternate system consisting of two phase-locked laser diodes. PMID:19777019

Lai, Y; Haus, H A; Yamamoto, Y

1991-10-01

419

Ward identities for amplitudes with reggeized gluons  

Energy Technology Data Exchange (ETDEWEB)

Starting from the effective action of high energy QCD we derive Ward identities for Green's functions of reggeized gluons. They follow from the gauge invariance of the effective action, and allow to derive new representations of amplitudes containing physical particles as well as reggeized gluons. We explicitly demonstrate their validity for the BFKL kernel, and we present a new derivation of the kernel.

Bartles, J. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Universidad Tecnica Federico Santa Maria, Valparaiso (Chile). Dept. de Fisica; Lipatov, L.N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; St. Petersburg Nuclear Physics Institute (Russian Federation); Vacca, G.P. [INFN, Sezione di Bologna (Italy)

2012-05-15

420

Annulus amplitude of FZZT branes revisited  

CERN Document Server

We revisit the annulus amplitude of FZZT branes with general matter sectors (r,s) using the recent development of matrix model and minimal Liouville gravity. Following the boundary description of the 1-matrix model and bulk resonance transformation between primary operators we find the consistency of the brane decomposition into (1,1)-branes. We also investigate the corresponding results obtained directly from the minimal Liouville gravity and demonstrate the perfect agreement with the matrix results.

Oh, Jae-Hyuk; Rim, Chaiho

2011-01-01