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1

Residual Amplitude Modulation in Interferometric Gravitational Wave Detectors  

CERN Document Server

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

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

2013-01-01

2

Amplitude Modulator Chassis  

Energy Technology Data Exchange (ETDEWEB)

The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.

Erbert, G

2009-09-01

3

Alternating-phase focusing with amplitude modulation  

Energy Technology Data Exchange (ETDEWEB)

We have previously developed a model of alternating-phase focusing (APF) applicable to ion linacs comprised of short independently controlled cavities. The main beam dynamical aspects of APF are adequately described by four parameters: Equilibrium synchronous phase, phase modulation amplitude, length of APF period, and incremental energy gain. In this paper we report on an extension of the analysis to include simultaneous modulation of the accelerating field amplitude. Two additional parameters are included: Relative phase between the amplitude and phase modulation and magnitude of the amplitude modulation. The effects of amplitude modulation on the stable regions and longitudinal acceptance are discussed.

Sagalovsky, L.; Delayen, J.R.

1993-08-01

4

Amplitude modulation of wind turbine noise  

CERN Document Server

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

Makarewicz, Rufin

2013-01-01

5

Amplitude-modulated fiber-ring laser  

DEFF Research Database (Denmark)

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

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

2000-01-01

6

Forward masking of amplitude modulation: Basic characteristics  

Science.gov (United States)

In this study we demonstrate an effect for amplitude modulation (AM) that is analogous to forward making of audio frequencies, i.e., the modulation threshold for detection of AM (signal) is raised by preceding AM (masker). In the study we focused on the basic characteristics of the forward-masking effect. Functions representing recovery from AM forward masking measured with a 150-ms 40-Hz masker AM and a 50-ms signal AM of the same rate imposed on the same broadband-noise carrier, showed an exponential decay of forward masking with increasing delay from masker offset. Thresholds remained elevated by more than 2 dB over an interval of at least 150 ms following the masker. Masked-threshold patterns, measured with a fixed signal rate (20, 40, and 80 Hz) and a variable masker rate, showed tuning of the AM forward-masking effect. The tuning was approximately constant across signal modulation rates used and consistent with the idea of modulation-rate selective channels. Combining two equally effective forward maskers of different frequencies did not lead to an increase in forward masking relative to that produced by either component alone. Overall, the results are consistent with modulation-rate selective neural channels that adapt and recover from the adaptation relatively quickly.

Wojtczak, Magdalena; Viemeister, Neal F.

2005-11-01

7

Amplitude Modulation Effects in Cardiac Signals  

CERN Multimedia

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

8

Amplitude and phase modulation of Moessbauer radiation  

International Nuclear Information System (INIS)

An expression has been obtained for spectral intensity of the Moessbauer radiation periodically modulated by transmitting through time-alternating layers with different complex refraction indices. The effect of modulation parameters on the spectral distribution of modulated radiation is analysed. It has been shown that interference should take place in the process of photon transmission from a source to an absorber through different ''time channels''.

1975-01-01

9

Relative Sideband Amplitudes Versus Modulation Index for Common Functions Using Frequency and Phase Modulation.  

Science.gov (United States)

The equations defining the amplitude of sidebands resulting from either frequency modulation or phase modulation by either square wave, sine wave, sawtooth or triangular modulating functions are presented. Spectral photographs and computer generated table...

F. Stocklin

1973-01-01

10

Parasitic amplitude modulation of stabilized CO/sub 2/ lasers  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation was made of parasitic amplitude modulation in a CO/sub 2/ laser with intracavity frequency modulation. This effect was due to periodic misalignment of the laser cavity during operation of a piezoelectric ceramic modulator. A method for controlling and minimizing the parasitic modulation was developed. Relationships were derived for the shift of the stabilized frequency due to such parasitic amplitude modulation and estimates were obtained for the case of a stabilized CO/sub 2//OsO/sub 4/ laser. It was found that the parasitic modulation could give rise to a dependence of the stabilized frequency on the phase relationships in the case of phase-sensitive detection in an automatic frequency control system of the laser.

Bazarov, E.; Gerasimov, G.; Gubin, V.; Starostin, N.; Fomin, V.

1981-07-01

11

Imaging cobalt nanoparticles by amplitude modulation atomic force microscopy: comparison between low and high amplitude solutions  

International Nuclear Information System (INIS)

In many situations of interest amplitude modulation AFM is characterized by the coexistence of two solutions with different physical properties. Here, we compare the performance of those solutions in the imaging of cobalt nanoparticles. We show that imaging with the high amplitude solution implies an irreversible deformation of the nanoparticles while repeated imaging with the low solution does not produce noticeable changes in the nanoparticles. Theoretical simulations show that the maximum tip-surface force in the high amplitude solution is about 14 nN while in the low amplitude solution is about -4 nN. We attribute the differences in the high and low amplitude images to the differences in the exerted forces on the sample.

2003-01-01

12

Amplitude Modulated Sinusoidal Signal Decomposition for Audio Coding  

DEFF Research Database (Denmark)

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

Christensen, M. G.; Jacobson, A.

2006-01-01

13

Cantilever dynamics in amplitude modulation AFM: continuous and discontinuous transitions  

International Nuclear Information System (INIS)

Transitions between the attractive and the repulsive force regimes for amplitude modulation atomic force microscopy (AFM) can be either discontinuous, with a corresponding jump in amplitude and phase, or continuous and smooth. During the transitions, peak repulsive and average forces can be up to an order of magnitude higher when these are discrete. Under certain circumstances, for example, when the tip radius is relatively large (e.g. R > 20-30 nm) and for high cantilever free amplitudes (e.g. A0 > 40-50 nm), the L state can be reached with relatively low set-points only (e.g. Asp/A0

2010-07-14

14

CARRIER-FREQUENCY HARMONIZATION STRUCTURE FOR ENHANCED AMPLITUDE MODULATION FUNCTION  

Directory of Open Access Journals (Sweden)

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

B.V.Subba Rao; P. Satyanarayanna

2013-01-01

15

Tailoring quantum superpositions with linearly polarized amplitude-modulated light  

CERN Multimedia

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

16

Effects of dust on amplitude modulation of kinetic Alfven waves  

International Nuclear Information System (INIS)

Effects of dust on the amplitude modulation of two possible types of kinetic Alfven waves, modified and dust kinetic Alfven waves, in a magnetized dusty plasma have been investigated. The appropriate nonlinear dispersion relations of the amplitude modulation predict that the carrier kinetic Alfven waves are modulationally unstable for long wave-length perturbations. It has been found that the parameter ? plays a significant role on the amplitude modulation of the waves, where ? is the ratio of the equilibrium number densities of the ions and the electrons and is a measure of the charge carried by the dust component. The maximum growth rate of the modulational instability increases with the parameter ?, whereas, the range of the perpendicular component of the modulation wavenumber K perpendicular to of the unstable wave remains almost constant for the case of dust kinetic Alfven waves. On the other hand, the maximum growth rate is almost constant with ?, while the range of K perpendicular to of the unstable wave drastically decreases for the case of modified kinetic Alfven waves. (orig.)

2001-01-01

17

Modulated Amplitude Waves in Collisionally Inhomogeneous Bose-Einstein Condensates  

CERN Multimedia

We investigate the dynamics of an effectively one-dimensional Bose-Einstein condensate (BEC) with the scattering length $a$ subjected to a spatially periodic modulation, $a=a(x) = a(x + L)$. This "collisionally inhomogeneous" BEC is described by a Gross-Pitaevskii (GP) equation with a nonlinearity coefficient that is a periodic function of $x$. We transform this GP equation into a constant-nonlinearity GP equation with an effective potential and study a class of the latter's extended wave solutions. For small inhomogeneities, the effective potential takes a form reminiscent of a superlattice, and the amplitude dynamics of the BEC's coherent structures are described by a nonlinear generalized Ince equation. In the small-amplitude limit, we use averaging to construct modulated amplitude wave (MAW) solutions, whose stability we subsequently examine using both numerical simulations of the original GP equation and fixed point computations with the MAWs as numerically exact solutions. We show that "on-site" solutio...

Porter, M A; Malomed, B A; Frantzeskakis, D J; Porter, Mason A.; Malomed, Boris A.

2006-01-01

18

Amplitude Modulation of Atomic Wavefunctions - Final Technical Report  

Energy Technology Data Exchange (ETDEWEB)

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

Cooke, William E.

2001-08-01

19

Flexible quadrature amplitude modulation with semiconductor optical amplifier and electroabsorption modulator.  

UK PubMed Central (United Kingdom)

Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a low-complexity modulator based on a semiconductor optical amplifier and electroabsorption modulator. Flexible amplitude/phase format transmission is achieved. The applicability of octary QAM for coherent optical access networks with sustainable 3 Gb/s per-user bandwidth is investigated for a long reach of 100 km, and its compatibility with a potentially high split is verified.

Schrenk B; Dris S; Bakopoulos P; Lazarou I; Voigt K; Zimmermann L; Avramopoulos H

2012-08-01

20

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

International Nuclear Information System (INIS)

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

1980-11-07

 
 
 
 
21

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

Energy Technology Data Exchange (ETDEWEB)

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

Kang, H.

1980-10-01

22

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

2013-01-01

23

Modulated amplitude waves in Bose-Einstein condensates.  

UK PubMed Central (United Kingdom)

We analyze spatiotemporal 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 MA; Cvitanovi? P

2004-04-01

24

Modulated amplitude waves in Bose-Einstein condensates  

International Nuclear Information System (INIS)

We analyze spatiotemporal 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.

2004-01-01

25

Quantifying dielectrophoretic nanoparticle response to amplitude modulated input signal  

International Nuclear Information System (INIS)

[en] A new experimental system and theoretical model have been developed to systematically quantify and analyse the movement of nanoparticles subjected to continuously pulsed, or amplitude modulated, dielectrophoretic (DEP) input signal. Modulation DEP-induced concentration fluctuations of fluorescently labelled 0.5 µm and 1.0 µm diameter latex nanospheres, localized near castellated electrode edges, were quantified using real-time fluorescence microscope dielectrophoretic spectroscopy. Experimental measurements show that the fluorescence fluctuations decrease as the modulation frequency increases-in agreement with model predictions. The modulation frequency was varied from 25 × 10-3 to 25 Hz and the duty-cycle ratios ranged from zero to unity. Two new parameters for characterizing DEP nanoparticle transport are defined: the modulation frequency bandwidth and the optimal duty-cycle ratio. The ‘on/off’ modulation bandwidth, for micrometre scale movement, was measured to be 0.6 Hz and 1.0 Hz for 1.0 µm and 0.5 µm diameter nanospheres, respectively. At these cut-off frequencies very little movement of the nanospheres could be microscopically observed. Optimal fluorescence fluctuations, for modulation frequencies ranging from 0.25 to 1.0 Hz, occurred for duty-cycle ratio values ranging from 0.3 to 0.7-agreeing with theory. The results are useful for automated DEP investigations and associated technologies.

2012-09-12

26

Linear dispersive pre-defined peak amplitude modulation of spectrally modulated Airy-based pulses.  

UK PubMed Central (United Kingdom)

Spectrally modulated Airy-based pulses peak amplitude modulation (PAM) in linear dispersive media is investigated, designed, and numerically simulated. As it is shown here, it is possible to design the spectral modulation of the initial Airy-based pulses to obtain a pre-defined PAM profile as the pulse propagates. Although optical pulses self-amplitude modulation is a well-known effect under non-linear propagation, the designed Airy-based pulses exhibit PAM under linear dispersive propagation. This extraordinary linear propagation property can be applied in many kinds of dispersive media, enabling its use in a broad range of experiments and applications.

Preciado MA

2013-06-01

27

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

28

Simultaneous amplitude and phase modulation by a discrete phase-only filter.  

UK PubMed Central (United Kingdom)

We propose a simultaneous amplitude and phase modulation method by a discrete phase-only filter. The proposed amplitude-phase filter can be realized by a discrete phase modulation of the diffractive optical element as well as a continuous phase modulation of the liquid crystal spatial light modulator. The fabricated amplitude-phase filter that has the six phase modulation levels shows a transfer efficiency of 75% regardless of the polarization state of the incident light. By using the proposed amplitude-phase filter, we demonstrate a temporal waveform conversion from sech(2) to super-Gaussian, which requires both amplitude and phase modulations.

Goto H; Konishi T; Itoh K

2009-03-01

29

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.

1993-01-01

30

Modulated Amplitude Waves in Bose-Einstein Condensates  

CERN Multimedia

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

31

Oblique amplitude modulation of dust-acoustic plasma waves  

CERN Document Server

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 criteria depend on the angle $\\theta$ between the modulation and propagation directions. Explicit expressions for the instability rate and threshold have been obtained in terms of the dispersion laws of the system. The possibility and conditions for the existence of different types of localized excitations have also been discussed.

Kourakis, I

2004-01-01

32

Oblique Amplitude Modulation of Dust-Acoustic Plasma Waves  

International Nuclear Information System (INIS)

[en] 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 criteria depend on the angle ? between the modulation and propagation directions. Explicit expressions for the instability rate and threshold have been obtained in terms of the dispersion laws of the system. The possibility and conditions for the existence of different types of localized excitations have also been discussed

2004-01-01

33

Oblique Amplitude Modulation of Dust-Acoustic Plasma Waves  

Energy Technology Data Exchange (ETDEWEB)

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 criteria depend on the angle {theta} between the modulation and propagation directions. Explicit expressions for the instability rate and threshold have been obtained in terms of the dispersion laws of the system. The possibility and conditions for the existence of different types of localized excitations have also been discussed.

Kourakis, I.; Shukla, P.K. [Ruhr-Univ., Bochum (Germany). Inst. fuer Theoretische Physik IV

2004-03-01

34

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)

1992-01-01

35

Semi-classical estimate of the residues of the scattering amplitude for long-range potentials  

International Nuclear Information System (INIS)

[en] In this paper, we study the residue of the scattering amplitude for the Schroedinger operator with long-range perturbation of the Laplacian, in the case where there are resonances exponentially close to the real axis. If the resonances are simple and under a separation condition, one proves that the residue of the scattering amplitude associated with a resonance ? is bounded by C(h)|Im ?|. Here C(h) denotes an explicit constant depending polynomially on h-1 and the number of resonances in a fixed box. This generalizes a recent result of Stefanov concerning compactly supported perturbations and isolated resonances

2003-04-18

36

Semi-classical estimate of the residues of the scattering amplitude for long-range potentials  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we study the residue of the scattering amplitude for the Schroedinger operator with long-range perturbation of the Laplacian, in the case where there are resonances exponentially close to the real axis. If the resonances are simple and under a separation condition, one proves that the residue of the scattering amplitude associated with a resonance {xi} is bounded by C(h)|Im {xi}|. Here C(h) denotes an explicit constant depending polynomially on h{sup -1} and the number of resonances in a fixed box. This generalizes a recent result of Stefanov concerning compactly supported perturbations and isolated resonances.

Michel, Laurent [Departement de Mathematiques Appliquees, Universite Bordeaux I, 351, Cours de la Liberation, 33405 Talence (France)

2003-04-18

37

Spatial spin resonance of polarized neutrons in amplitude-modulated magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

The spatial spin resonance of polarized neutrons is investigated in a system of two magnetic fields, the configurations of an amplitude-modulated field alternating in space and a guide field with a gradient. The case of sine-cosine modulation is considered. It is shown that amplitude modulation of the guide magnetic field allows one to change the line width of the resonator smoothly up to {Delta}{lambda}/{lambda}=0.3. (orig.).

Grigoriev, S.V. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Runov, V.V. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Okorokov, A.I. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Tretyakov, A.D. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Gubin, O.A. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Kopitsa, G.P. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Runova, M.K. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation)

1997-04-21

38

Intra and intersubject variability in auditory steady-state response amplitude with high modulation rates to 1000 Hz amplitude modulated and tone pip stimuli.  

UK PubMed Central (United Kingdom)

OBJECTIVE: This study set out to provide further information on how high modulation/stimulus rates affect the auditory steady-state response (ASSR) amplitude for a 1000-Hz tone, and how this effect varies between individuals. Both sinusoidal amplitude modulated tones and tone pip stimuli were investigated. DESIGN: Modulation/stimulus rates were 70, 80, and 90 Hz and the peak to peak stimulus levels were matched for the two different types of stimuli, at 90.5 dBSPLppe. STUDY SAMPLE: The study was carried out on fourteen normally-hearing adults (9 males and 5 females) RESULTS: Overall the ASSR amplitude to the two types of stimuli was similar. In general there was an increasing response amplitude between rates of 70 and 90 Hz; The relationship between the amplitude of the response and the modulation /stimulus rate varied considerably between subjects. CONCLUSIONS: Optimum stimulus rates based on group data may not give the best rate in a significant proportion of subjects. Currently tone pip ABR is the primary method used in assessing hearing in babies. Finding a way of avoiding suboptimal stimulus rates for '80-Hz' ASSR in babies will improve the likelihood of ASSR being seen as an alternative.

Foster M; Stevens J; Brennan S

2013-07-01

39

Method for assessing the amplitude modulation of the stationary planetary waves  

Directory of Open Access Journals (Sweden)

Full Text Available This short-communication presents a new method for assessing the amplitude modulation of the stationary planetary waves (SPWs). The suggested procedure allows estimating the contribution of the amplitude modulated SPWs to the field of the zonally travelling planetary waves. The root of the method consists in calculating of a quantity that is analogous to 2-D Lomb-Scargle amplitude spectrum and also the relative error of the approximation. The amplitude "spectra" of the SPWs give information about the period(s) of modulation, while the relative errors - define the coefficient(s) of modulation. The suggested method is applied to the UKMO temperature data for the Arctic winter of 2004–2005.

P. Mukhtarov; D. Pancheva; B. Andonov

2009-01-01

40

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

Directory of Open Access Journals (Sweden)

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

K. Baumgärtel

2013-01-01

 
 
 
 
41

Periodic self-accelerating beams by combined phase and amplitude modulation in the Fourier space.  

UK PubMed Central (United Kingdom)

We propose and demonstrate the generation of periodic self-accelerating beams through both phase and amplitude modulation in the Fourier space. For small amplitude variations, an accelerating beam still follows a smooth convex trajectory, which can be traced by acting on the spectral phase only. However, large modulations such as those generated from the Heaviside function with a zero amplitude distribution partially modify the convex trajectory due to the appearance of straight-line paths. Furthermore, periodic self-accelerating beams along convex trajectories are realized by employing an array of "spectral wells" in both the paraxial and nonparaxial regimes.

Hu Y; Bongiovanni D; Chen Z; Morandotti R

2013-09-01

42

Amplitude modulator of radio frequency system for 1.3 GeV Electron Synchrotron  

International Nuclear Information System (INIS)

[en] The amplitude modulator for the 8F68 VHF high power tetrode tube has been designed and constructed. The modulator was constructed with solid components such as transistors and integrated circuits. In case of changing circuit elements of the modulator to solid components from tubes, many attentions are paid for preventing the noise and the over load, due to connection between the low power circuits (modulator) and high power circuits (VHF amplifier). The new modulator is constructed with taking careful consideration into selection of the method of the power control and the protection system. (auth.)

1977-01-01

43

Constant Amplitude Modulation for Wireless Channels at 60 GHz  

UK PubMed Central (United Kingdom)

The aim of this thesis was to simulate the performance of an equalized GaussianMinimum Shift Keying (GMSK) signal for indoor applications at 60 GHz frequencyband, with noise and Intersymbol interference (ISI). A Decision Feedback Equalizer(DFE) was designed to cope with the ISI and noise. The system aims at a data rate of271 Mbits/s. The binary GMSK modulation has normalized bandwidth BT = 0.3,memory length L = 3 and modulation index h = .A bit error rate (BER) performance lower than 10-4at E b / N o = 17 dB was achievedusing a DFE with 18 feedforward taps and 32 feedback taps. We did not find any otherDFE that performed better than that. The channel used for simulations has 39 symbolspaced taps with rms delay spread # RMS # 24 ns. We used the Saleh-Valenzuela model tosimulate the indoor channel.We used burst equalization with packet size equal to 20 kbits. The training sequencelength was equal to 1000 bits. Variations of frame size showed that a 40 kbits framecould be considered with slightly worse performance.iiAcknowledgments:I am very thankful to my supervisor, Tommy Svensson, for his valuable consultationand support throughout this thesis work. Thanks Tommy for paving the road of mywork during the last 5 months.I would also like to sincerely express my gratitude to my examiner, Prof. ArneSvensson.Many thanks go to all the Ph.D. students at the Signals and Systems Department whohelped me answering my constant doubts. Specially, I would like to thank SorourFalahati and Maxime Flament for their support.I take this opportunity to express my indebtedness to the Stint Foundation, whosponsored my studies here in Sweden. Special thanks go to Mr. Gustavo Perrusquia andto Angelica Martensson from the International office...

Jos Aloysio; Souza Jnior; Tommy Svensson; Arne Svensson

44

The effect of temporal asymmetry on amplitude modulation detection using pure-tone carriers (L).  

UK PubMed Central (United Kingdom)

The effect of temporal asymmetry on amplitude modulation detection was studied using sawtooth modulators with rising (ramped) or falling (damped) temporal envelopes within each period of modulation. For pure-tone carriers, damped modulation was more detectable than ramped modulation for a 5-kHz carrier (by a threshold difference of 3.2 dB on average) but not for a 1-kHz carrier. The threshold difference obtained at 5 kHz between the ramped and damped modulators was consistent across modulation rates (8-128 Hz). This carrier frequency dependence suggests that the effect of temporally asymmetry on modulation detection originates from envelope-based, within-channel mechanisms.

Shen Y; Lentz JJ

2011-11-01

45

Basic causes of amplitude modulation in climatic/weather parameters  

International Nuclear Information System (INIS)

The continuous interaction between the Earth's spinning motion and energy from the Sun gives rise to some (heat) energy oscillations in the Earth-atmosphere system (Njau, 1985a; 1985b; 1986a; 1986b). Recent results of large scale analysis of East African climatic records have proved that these oscillations significantly link the Sun to climatic/weather variations by systematically modulating key climatic/weather parameters like rainfall and air temperature (Njau, 1987a; 1987b; 1987c; 1987e; 1987f). In this paper, we re-develop the latter proof using a very different approach based upon theoretical analysis. The analysis has confirmed a general law suggested earlier (Njau, 1987d), that, with an exception of the diurnal cycle, any permanent cycle in the net solar energy incident upon a given part of the Earth-Atmosphere system gives rise to a quasi-permanent cycle whose period is approximately twice that of the former. Quasi-biennial as well as double sunspot cycles are shown to be a possible result of this general law. (author). 35 refs, 1 fig., 2 tabs.

1987-01-01

46

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

International Nuclear Information System (INIS)

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

2004-01-01

47

Optimization of magnetic field sweep and field modulation amplitude for continuous-wave EPR oximetry.  

UK PubMed Central (United Kingdom)

For continuous-wave electron paramagnetic resonance spectroscopy, what settings of magnetic field sweep width and field modulation amplitude yield the best accuracy in estimated linewidth? Statistical bounds on estimation error presented in this work provide practical guidance: set the sweep width and modulation amplitude to 8 and 4 times the half-width half-maximum linewidth, ?, respectively. For unknown linewidths in the range [?(min),?(max)] the worst-case estimation error is minimized by using settings designed for ?(max). The analysis assumes a Lorentzian lineshape and a constant modulation amplitude across the extent of the irradiated paramagnetic probe. The analytical guidelines are validated using L-band spectroscopy with a particulate LiNc-BuO probe.

Palmer J; Potter LC; Ahmad R

2011-04-01

48

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.

1192-01-00

49

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

Energy Technology Data Exchange (ETDEWEB)

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

Ow, Y.S., E-mail: g0601170@nus.edu.s [Physics Department, National University of Singapore, Lower Kent Ridge Road, Singapore 119260 (Singapore); Breese, M.B.H.; Leng, Y.R.; Azimi, S.; Teo, E.J. [Physics Department, National University of Singapore, Lower Kent Ridge Road, Singapore 119260 (Singapore); Sun, X.W. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

2010-05-01

50

Characterizing Alzheimer's Disease Severity via Resting-Awake EEG Amplitude Modulation Analysis  

Science.gov (United States)

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

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

2013-01-01

51

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

Science.gov (United States)

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

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

2013-08-27

52

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

UK PubMed Central (United Kingdom)

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

Fraga FJ; Falk TH; Kanda PA; Anghinah R

2013-01-01

53

Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus.  

UK PubMed Central (United Kingdom)

Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (?5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation frequency are (95% CI) 11.6% (10.0-13.1) for PL units, 9.8% (8.2-11.5) for CT units, and 10.8% (8.4-13.2) for CS units. The most sensitive guinea-pig VCN single unit AM detection thresholds are similar to human psychophysical performance (?3% AM), while the mean neurometric thresholds approach whole animal behavioural performance (?10% AM).

Sayles M; Füllgrabe C; Winter IM

2013-07-01

54

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; David Martínez-Martín; Mariano Cuenca; John Melcher; Arvind Raman; Julio Gómez-Herrero

2012-01-01

55

Possible Control of Sugarbeet Pathogen Sclerotium rolfsii Sacc. By Elf Amplitude Modulated Waves  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of extremely low frequency (ELF) amplitude modulated (AM) square waves in the frequency range 0.5 to 20 Hz on the S. rolfsii activity was studied. The effect of time of exposure to ELF AM waves on the linear growth and biomass gain of the fungus in vivo and in vitro w...

Mohamed A. Rizk

56

Stationary modulated-amplitude waves in the 1-D complex Ginzburg-Landau equation  

CERN Document Server

We reformulate the one-dimensional complex Ginzburg-Landau equation as a fourth order ordinary differential equation in order to find stationary spatially-periodic solutions. Using this formalism, we prove the existence and stability of stationary modulated-amplitude wave solutions. Approximate analytic expressions and a comparison with numerics are given.

Lan, Y; Cvitanovic, P; Lan, Yueheng; Garnier, Nicolas; Cvitanovic, Predrag

2002-01-01

57

Amplitude-modulated sinusoidal microchannels for observing adaptability in C. elegans locomotion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we present a movement-based assay to observe adaptability in Caenorhabditis elegans locomotion behavior. The assay comprises a series of sinusoidal microchannels with a fixed wavelength and modulating (increasing or decreasing) amplitude. The channel width is comparable to the body di...

Parashar, Archana; Lycke, Roy; Carr, John A.; Pandey, Santosh

58

VERY LOW FREQUENCY 16 HZ AMPLITUDE MODULATED ELECTROMAGNETIC RADIATION INCREASES CALCIUM EFFLUX FROM THE FROG HEART  

Science.gov (United States)

The effects of continuous and amplitude-modulated radiofrequency electromagnetic waves on calcium efflux from 45Ca preloaded frog hearts were examined. rog hearts, electrically stimulated at their natural beating frequency, were exposed for 30 min to 240 MHz radiowaves in a Crawf...

59

Optimal Reception of 64 Quadrature Amplitude Modulation in High-Speed Downlink Packet Access  

Digital Repository Infrastructure Vision for European Research (DRIVER)

High-speed downlink packet access (HSDPA) is a feature introduced to the universal mobile telecommunications system (UMTS) in 2002. It allows data rates of up to 14.4 Mbps in the downlink. In 2007 new features were standardized to HSDPA, including 64 Quadrature Amplitude Modulation (64-QAM). 64-QAM...

Pitkänen, Sampo

60

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

UK PubMed Central (United Kingdom)

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

Ribeiro NS; Cavacalcante AL; Gallep CM; Conforti E

2010-12-01

 
 
 
 
61

Theoretical design of amplitude-modulated pulses for spin decoupling in nuclear magnetic resonance  

International Nuclear Information System (INIS)

The problem of low-power spin decoupling over a broad range of chemical shifts in liquid-state nuclear magnetic resonance (NMR) is addressed through the design of periodic amplitude-modulated irradiation schemes. A principal feature of these is the composition of each decoupling period which contains a single modulated pulse in place of a composite-pulse train of the kind used traditionally. To satisfy the theoretical criterion for decoupling, the pulse amplitude is shaped such that the propagator is made cyclic and broadband, meaning here that it equals the identity matrix over a frequency range which is broad compared to the root-mean-square (RMS) pulse amplitude. The method of design is based on the use of the Floquet formalism to provide insight into the influence of the modulation on the dynamics of the irradiated spin 1-2 Modulation functions formed from simple Fourier series are derived in the first instance using perturbation theory to impose the required cyclicity on the propagator. Broad bandwidth solutions are then obtained by the addition of higher-order Fourier components. Finally, numerical refinement of a selected solution is shown to raise the decoupling quality to the standards acceptable in routine high-resolution NMR. (Author).

1996-01-01

62

A Generalized Model of Nonlinear Dynamics in Combined Frequency-Amplitude Modulators  

CERN Multimedia

Research in the area of communications systems, and more in general in the field of information theory, is constantly pursued since new physical mechanisms for the excitation of stable microwave oscillations, such as those based on spin-transfer effects, have been demonstrated to be feasible, demanding in turn for a deeper understanding of the underlying nonlinear dynamics. Here we formulate a generalized theoretical model to describe the behavior of combined frequency-amplitude modulators whose characteristic parameters exhibit a nonlinear dependence on the input modulating signal. The derived analytical solution may give a satisfactory explanation of recent laboratory observations on magnetic oscillators, indicating that those dynamics cannot be ascribed to a pure frequency modulation process. The model agrees with results of micromagnetic calculations. Because the theory has been developed independently of the mechanism causing the nonlinearities, it encompasses the description of modulation processes occu...

Consolo, G; Lopez-Diaz, L; Nizzoli, F; Giovannini, L; Valenti, G; Azzerboni, B

2009-01-01

63

Improving the performance of bright quantum dot single photon sources using temporal filtering via amplitude modulation.  

Science.gov (United States)

Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit nonideal 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 systems based on single solid-state quantum emitters, which often suffer from excess dephasing and multi-photon background emission. PMID:23466520

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

2013-01-01

64

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

65

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

Science.gov (United States)

Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit nonideal 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 systems based on single solid-state quantum emitters, which often suffer from excess dephasing and multi-photon background emission.

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

2013-01-01

66

Stability, resolution, and ultra-low wear amplitude modulation atomic force microscopy of DNA: Small amplitude small set-point imaging  

Science.gov (United States)

A way to operate fundamental mode amplitude modulation atomic force microscopy is introduced which optimizes stability and resolution for a given tip size and shows negligible tip wear over extended time periods (~24 h). In small amplitude small set-point (SASS) imaging, the cantilever oscillates with sub-nanometer amplitudes in the proximity of the sample, without the requirement of using large drive forces, as the dynamics smoothly lead the tip to the surface through the water layer. SASS is demonstrated on single molecules of double-stranded DNA in ambient conditions where sharp silicon tips (R ~ 2-5 nm) can resolve the right-handed double helix.

Santos, Sergio; Barcons, Victor; Christenson, Hugo K.; Billingsley, Daniel J.; Bonass, William A.; Font, Josep; Thomson, Neil H.

2013-08-01

67

A Perturbative Analysis of Modulated Amplitude Waves in Bose-Einstein Condensates  

CERN Multimedia

We apply Lindstedt's method and multiple scale perturbation theory to analyze spatio-temporal structures in nonlinear Schr\\"odinger equations and thereby study the dynamics of quasi-one-dimensional Bose-Einstein condensates (BECs) with mean-field interactions. We determine the dependence of the intensity of modulated amplitude waves (MAWs) on their wave number. We also 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

68

Modulated Amplitude Waves and Defect Formation in the One-Dimensional Complex Ginzburg-Landau Equation  

CERN Multimedia

The transition from phase chaos to defect chaos in the complex Ginzburg-Landau equation (CGLE) is related to saddle-node bifurcations of modulated amplitude waves (MAWs). First, the spatial period P of MAWs is shown to be limited by a maximum P_SN which depends on the CGLE coefficients; MAW-like structures with period larger than P_SN evolve to defects. Second, slowly evolving near-MAWs with average phase gradients $\

Brusch, L; Van Hecke, M; Zimmermann, M G; Baer, M E; Brusch, Lutz; Torcini, Alessandro; Hecke, Martin van; Zimmermann, Martin G.; Baer, Markus

2001-01-01

69

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

UK PubMed Central (United Kingdom)

The main goal of this study was to study the performance of fuzzy logic controllers combined with simplified hybrid amplitude/pulse-width (AM/PW) modulation to regulate muscle force via nerve electrical stimulation. The recruitment curves with AM/PW and AM modulations were constructed for the calf muscles of rabbits. Integrated with the modulation methods, a proportional-integral-derivative (PID) and three fuzzy logic controllers were designed and applied for the electrical stimulation of tibial nerves to control the ankle torque under isometric conditions. The performance of the two modulation methods combined with the four controllers was compared when the ankle was fixed at three positions for both in vivo experiments and model simulations using a nonlinear muscle model. For the animal experiments, AM/PW modulation performed better than AM modulation alone. The fuzzy PI controller performed marginally better and was resistant to external noises, though it tended to have a larger overshoot. The performance of the controllers had a similar trend in the three different joint positions, and the simulation results with the nonlinear model matched the experimental results well. In conclusion, AM/PW modulation improved controller performance, while the contribution of fuzzy logic was only marginal.

Lin CC; Liu WC; Chan CC; Ju MS

2012-04-01

70

Estimating critical bandwidths of temporal sensitivity to low-frequency amplitude modulation.  

UK PubMed Central (United Kingdom)

Auditory filter bandwidths are measured for a temporal process using an amplitude-modulation detection task. The signal is a 200?Hz wide, sinusoidally amplitude-modulated band of noise centered within an unmodulated notched-noise masker. A modulation rate of 10?Hz is used to avoid possible information loss at more central processing levels for high modulation rates. Threshold functions are obtained for 10-14 notch widths for each of four different center frequencies (0.6, 1, 2, and 4?kHz) to determine the maximum notch width at which the masker has an effect. The ratio of center frequency to maximum notch width is ~2 at all center frequencies. It is proposed that the bandwidths observed in temporal tasks, which are consistently greater than expected from the viewpoint of critical band theory, be characterized as "temporal critical bands." This proposal does not oppose, but provides a complement to the traditional critical band obtained in tasks involving spectral discrimination.

Shim AI; Berg BG

2013-05-01

71

High performance laser linewidth broadening for stimulated Brillouin suppression with zero parasitic amplitude modulation  

Science.gov (United States)

To enable optimum network transmission, the ideal is to launch as high laser power as possible into the optical fiber, to overcome the effects of fiber attenuation and maintain an acceptable signal to noise ratio. Launching high powers into a fiber however, results in unwanted nonlinear effects. Stimulated Brillouin scattering (SBS) is one of the nonlinear effects which reflects a significant proportion of the transmitted optical power back to the transmitter, degrading the system severely. This paper reports the development of a digitally selected supermode distributed Bragg reflector monolithic laser chip which can provide significant linewidth broadening using a pure frequency modulation technique by application of a dither current. By modifying a small segment of the laser chip material refractive index, it produces a modulation of the longitudinal mode and hence laser frequency; the monolithic laser chip has reduced the effects of SBS significantly with very little parasitic amplitude modulation.

Mitchell, P.; Janssen, A.; Luo, J. K.

2009-05-01

72

Low frequency amplitude modulated microwave fields change calcium efflux rates from synaptosomes  

International Nuclear Information System (INIS)

Calcium (45Ca2+) efflux from preloaded synaptosomes was studied with a continuous perfusion technique and the rate constants of a two-phase efflux process calculated. When 16-Hz sinusoidally amplitude modulated 450-MHz microwave field (maximal incident intensity 0.5 mW/cm2, modulation depth 75%) was applied during the second phase, the rate constant increased by 38%. Unmodulated or 60-Hz modulated signals were not effective. This microwave field-induced change can be distinguished from CaCl2-stimulated 45Ca2+ efflux which is most probably derived intracellularly. These data suggest that the microwave-field induced change in calcium efflux probably did not involve intracellular calcium. Also, this change in the dynamic property of synaptosomes did not require gross anatomically intact tissue as a substrate for field-tissue interaction

1982-01-01

73

Nonlinear wave number shift and modulational instability for large amplitude waves in a relativistic magnetised plasma  

International Nuclear Information System (INIS)

Properties of large amplitude waves in a relativistic magnetised plasma are studied using the method of reductive perturbation. The plasma under consideration consists of warm adiabatic ions and isothermal warm electrons, under the influence of a magnetic field. A consideration of large amplitude waves demands study of the relativistic situation. In the present case both the electrons and ions are considered to be relativistic. A KdV equation is derived from which a nonlinear Schroedinger equation is deduced by further scaling. Lastly an expression is derived for nonlinear wave number shift, critical angle of propagation and the condition for modulational instability. This analysis is applicable to both laboratory and space plasmas. 18 refs., 2 figs.

1992-01-01

74

Evaluation of two computational models of amplitude modulation coding in the inferior colliculus.  

UK PubMed Central (United Kingdom)

Two computational models replicating amplitude-modulation encoding in the inferior colliculus (IC) are presented and compared. Neurons in this nucleus are modeled as point neurons using Mc Gregor equations, and receive depolarizing currents from action potentials delivered by stellate cells (chopper units) in the cochlear nucleus (CN). Stellate cells are modeled using modified Hodgkin-Huxley equations and receive inputs from a peripheral auditory model. The CN models of the two proposed architectures are characterized by an important dispersion of cellular characteristics, and therefore by various cellular best modulation frequencies (BMFs) ranging from 60 to 300 Hz. In contrast with the previous model proposed by [M.J. Hewitt, R. Meddis, A computer model of amplitude-modulation sensitivity of single units in the inferior colliculus, J. Acoust. Soc. Am. 95 (1994) 2145], each IC cell model receives convergent input from stellate cells with various BMFs. This approach assumes therefore minimal constraints on the model architecture and cell characteristics. The two models differ in terms of the neuronal structure of the IC, composed of 1 or 2 layers of point neurons acting as coincidence detectors. Each model is evaluated using two metrics: mean firing rate and modulation gain. Rate and temporal modulation transfer functions (r-MTFs and t-MTFs, respectively) are simulated and compared with physiological data. Simulations reveal that (i) an important dispersion of BMFs in the CN cells providing input to IC cells yields plausible IC cells responses to AM stimuli, (ii) the 2-layer IC structure yields the best approximation of IC responses measured in vivo.

Guérin A; Jeannès Rle B; Bès J; Faucon G; Lorenzi C

2006-01-01

75

Evaluation of two computational models of amplitude modulation coding in the inferior colliculus.  

Science.gov (United States)

Two computational models replicating amplitude-modulation encoding in the inferior colliculus (IC) are presented and compared. Neurons in this nucleus are modeled as point neurons using Mc Gregor equations, and receive depolarizing currents from action potentials delivered by stellate cells (chopper units) in the cochlear nucleus (CN). Stellate cells are modeled using modified Hodgkin-Huxley equations and receive inputs from a peripheral auditory model. The CN models of the two proposed architectures are characterized by an important dispersion of cellular characteristics, and therefore by various cellular best modulation frequencies (BMFs) ranging from 60 to 300 Hz. In contrast with the previous model proposed by [M.J. Hewitt, R. Meddis, A computer model of amplitude-modulation sensitivity of single units in the inferior colliculus, J. Acoust. Soc. Am. 95 (1994) 2145], each IC cell model receives convergent input from stellate cells with various BMFs. This approach assumes therefore minimal constraints on the model architecture and cell characteristics. The two models differ in terms of the neuronal structure of the IC, composed of 1 or 2 layers of point neurons acting as coincidence detectors. Each model is evaluated using two metrics: mean firing rate and modulation gain. Rate and temporal modulation transfer functions (r-MTFs and t-MTFs, respectively) are simulated and compared with physiological data. Simulations reveal that (i) an important dispersion of BMFs in the CN cells providing input to IC cells yields plausible IC cells responses to AM stimuli, (ii) the 2-layer IC structure yields the best approximation of IC responses measured in vivo. PMID:16289669

Guérin, Alexandre; Jeannès, Régine Le Bouquin; Bès, Julien; Faucon, Gérard; Lorenzi, Christian

2005-11-11

76

Simultaneous measuring of Doppler frequency shift and group delay time by means of amplitude-modulated LFM-signal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

New method of the simultaneous measurement of the frequency dependencies of Doppler shift and group delay time of separate ionosphere modes by means of amplitude modulated chirp signal is presented in this paper. The algorithms for data processing are presented.

Kolchev, A. A.; Mari State University; Volga State University of Technology; Nedopekin, A. E.; Mari State University

77

Improving Bandwidth Efficiency of Indoor Visible Light Communication by M-ary Return-to-zero Optical Pulse Amplitude Modulation  

Directory of Open Access Journals (Sweden)

Full Text Available In order to solve the limitation of data rate caused by long rise and fall time of light emitting diodes, m-ary return-to-zero optical pulse amplitude modulation is proposed in this paper for improving the bandwidth efficiency of indoor visible light communication. M-ary return-to-zero optical pulse amplitude modulation transmits information through a subtle change of illumination intensity and supports both flicker mitigation and dimming control functions. An indoor communication link establishing process is introduced as a parameter training method based on the principle of successive approximation. Theoretical analysis shows that, m-ary return-to-zero optical pulse amplitude modulation can be used to achieve higher bandwidth efficiency without sacrificing the symbol error rate and bit error rate performance of an indoor visible light communication system. When the ratio of a_slot-a_BS is 0.1, then m-ary return-to-zero optical pulse amplitude modulation can provide 1.47 times bandwidth efficiency than that of on-off keying, 3.5 times than that of digital pulse interval modulation and 5.9 times than that of pulse position modulation. M-ary return-to-zero optical pulse amplitude modulation can be used as a candidate bandwidth efficiency modulation scheme to improving data rate of an indoor visible light communication system.

Guanghui Ren; Shengyang He; Yunlong Yang

2013-01-01

78

Rotation of non-spherical micro-particles by amplitude modulation of superimposed orthogonal ultrasonic modes.  

UK PubMed Central (United Kingdom)

Contactless rotation of non-spherical particles has been modeled and experimentally achieved using ultrasonic manipulation. For this purpose an acoustic radiation torque was generated by a time-varying pressure field resulting in a change of orientation of the potential well. The rotation method is based on amplitude modulation of two orthogonal ultrasonic modes. The force potential field has been used to evaluate the different modes and actuations to achieve rotation. Experiments have been performed in micro devices with copolymer particles and glass fibers at frequencies in the megahertz range. A continuous rotation was successfully demonstrated and the method allowed to stop the rotation at arbitrary angular positions.

Schwarz T; Petit-Pierre G; Dual J

2013-03-01

79

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

UK PubMed Central (United Kingdom)

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.

Gramse G; Edwards MA; Fumagalli L; Gomila G

2013-10-01

80

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

Science.gov (United States)

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. PMID:24061045

Gramse, G; Edwards, M A; Fumagalli, L; Gomila, G

2013-09-24

 
 
 
 
81

Amplitude modulation reflectometer for FTU; Riflettometro a modulazione di ampiezza per FTU  

Energy Technology Data Exchange (ETDEWEB)

Amplitude modulation (AM) reflectometry is a modification of the classical frequency sweep technique which allows to perform unambiguous phase delay measurements. An eight-channel AM reflectometer has been realized for the measurement of density profiles on the FTU tokamak in the range. The characteristics of the instrument have been determined in extensive laboratory tests; particular attention has been devoted to the effect of interference with parasitic reflections. The reflectometer is now operating on FTU. Some examples of the first experimental data are discussed.

Zerbini, M.; Buratti, P.; Centioli, C. [ENEA, Centro Ricerche Frascati, Rome (Italy). Dip. Energia; Amadeo, P.

1995-06-01

82

Application of multiscale amplitude modulation features and fuzzy C-means to brain-computer interface.  

UK PubMed Central (United Kingdom)

This study proposed a recognized system for electroencephalogram (EEG) data classification. In addition to the wavelet-based amplitude modulation (AM) features, the fuzzy c-means (FCM) clustering is used for the discriminant of left finger lifting and resting. The features are extracted from discrete wavelet transform (DWT) data with the AM method. The FCM is then applied to recognize extracted features. Compared with band power features, k-means clustering, and linear discriminant analysis (LDA) classifier, the results indicate that the proposed method is satisfactory in applications of brain-computer interface (BCI).

Hsu WY; Li YC; Hsu CY; Liu CT; Chiu HW

2012-01-01

83

Quantum quadrature amplitude modulation system and its applicability to coherent-state quantum cryptography  

Science.gov (United States)

The quadrature amplitude modulation (QAM) signal of coherent state of light is applied to the quantum stream cipher by Y-00 protocol. We first discuss on the performance of the square-root measurement (SRM) for the QAM signals in comparison with the optimum receiver. It is shown that the quantum stream cipher with the QAM signals is designed by using the SRM, taking account of the ciphertext-only attack and the known/chosen plain attack. Furthermore, the modification of the quantum stream cipher with the QAM signals is considered.

Kato, Kentaro; Hirota, Osamu

2005-08-01

84

Computer-guided alignment I : Phase and amplitude modulation of alignment-influenced optical wavefront  

Science.gov (United States)

As the first part of a development programme on computer-guided alignment (CGA), we model the alignment influence on the optical wavefront in terms of the phase and amplitude modulation. This modulation is derived from the interaction between alignment parameters and influence functions, both expressed in complex form. The alignment influence model is used to approximate the ray-traced target wavefront of a randomly mis-aligned multi-element system. The approximated wavefront shows a factor of ~ 100 improvement in predicting the target, when coupled non-linear influences among elements are included. This demonstrates the significance of the inter-element effect. We discuss the possibility of adopting the model for rectifying mis-alignment of multi-element systems.

Lee, Hanshin; Dalton, Gavin B.; Tosh, Ian A.; Kim, Sug-Whan

2007-03-01

85

Matter-wave scattering on an amplitude-modulated optical lattice  

Science.gov (United States)

We experimentally study the scattering of guided matter waves on an amplitude-modulated optical lattice. We observe different types of frequency-dependent dips in the asymptotic output density distribution. Their positions are compared quantitatively with numerical simulations. A semiclassical model that combines local Floquet-Bloch bands analysis and Landau-Zener transitions provides a simple picture of the observed phenomena in terms of elementary Floquet photon absorption-emission processes and envelope-induced reflections. Finally, we propose and demonstrate the use of this technique with a bichromatic modulation to design a tunable subrecoil velocity filter. Such a filter can be transposed to all species since it does not rely on a specific internal level configuration of the atoms.

Cheiney, P.; Fabre, C. M.; Vermersch, F.; Gattobigio, G. L.; Mathevet, R.; Lahaye, T.; Guéry-Odelin, D.

2013-01-01

86

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

87

High temporal resolution dynamic mapping of instantaneous EEG amplitude modulation after tone-burst auditory stimulation.  

Science.gov (United States)

A new method of instantaneous EEG analysis based on amplitude modulation (AM-EEG) was applied to analyze the AM-EEG changes in the alpha frequency band (8.20-12.89 Hz) for successive 5 ms epochs. Repeated auditory tone-burst stimuli (of 220 ms duration) were presented at fixed 2.56 second intervals to 12 attending right-handed young female volunteers, who were EEG-recorded over 19 EEG channels at 200 Hz sampling frequency. The time-course of functional activation was characterized in terms of percent decrease in instantaneous amplitude modulation, as compared to baseline, in analogy with the classical event-related desynchronization paradigm. A dynamic sequence of the successive 122 AM-EEG maps obtained for the 610 ms from beginning of tone-burst was stored and later animated on PC microcomputer. Topological changes among successive maps were extracted into 40 specific AM-EEG maps. Early left temporal and centro-temporal activation was observed, followed first by strong bilateral frontal, and then by left temporal activation. These changes induced by a warning tone-burst are discussed in terms of functional neurophysiology. The present method therefore allows an improved time-resolution for functional brain activation paradigms. PMID:10642012

Etévenon, P; Lebrun, N; Clochon, P; Perchey, G; Eustache, F; Baron, J C

1999-01-01

88

High temporal resolution dynamic mapping of instantaneous EEG amplitude modulation after tone-burst auditory stimulation.  

UK PubMed Central (United Kingdom)

A new method of instantaneous EEG analysis based on amplitude modulation (AM-EEG) was applied to analyze the AM-EEG changes in the alpha frequency band (8.20-12.89 Hz) for successive 5 ms epochs. Repeated auditory tone-burst stimuli (of 220 ms duration) were presented at fixed 2.56 second intervals to 12 attending right-handed young female volunteers, who were EEG-recorded over 19 EEG channels at 200 Hz sampling frequency. The time-course of functional activation was characterized in terms of percent decrease in instantaneous amplitude modulation, as compared to baseline, in analogy with the classical event-related desynchronization paradigm. A dynamic sequence of the successive 122 AM-EEG maps obtained for the 610 ms from beginning of tone-burst was stored and later animated on PC microcomputer. Topological changes among successive maps were extracted into 40 specific AM-EEG maps. Early left temporal and centro-temporal activation was observed, followed first by strong bilateral frontal, and then by left temporal activation. These changes induced by a warning tone-burst are discussed in terms of functional neurophysiology. The present method therefore allows an improved time-resolution for functional brain activation paradigms.

Etévenon P; Lebrun N; Clochon P; Perchey G; Eustache F; Baron JC

1999-01-01

89

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

1982-01-01

90

Research proposal on: amplitude modulated reflectometry system for the JET divertor  

Energy Technology Data Exchange (ETDEWEB)

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 present in most reflectometers during the last years is the need for a coherent tracking of the phase delay: fast density fluctuations and strong modulation on the amplitude of the reflected signal usually 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 onospheric studies and recently also proposed for fusion plasmas. The main advantage is to allow the use of millimeter wave reflectometry with moderate phase shifts ( {approx} 2{pi} ). (Author) 2 refs.

Sanchez, J.; Branas, B.; Estrada, T.; Luna, E. de la

1992-07-01

91

Excitation of large-amplitude parametric resonance by the mechanical stiffness modulation of a microstructure  

Science.gov (United States)

In this work we report on an approach allowing efficient parametric excitation of large-amplitude stable oscillations of a microstructure operated by a parallel-plate electrode, and present results of a theoretical and experimental investigation of the device. The frame-type structure, fabricated from a silicon on insulator (SOI) substrate using deep reactive ion etching (DRIE), consists a pair of cantilever-type suspensions connected at their ends by a link. The time-varying electrostatic force applied to the link by a parallel-plate electrode is transformed into a periodic tension of the beams, resulting in the modulation of their flexural stiffness and consequently the mechanical parametric excitation of the structure. The lateral compliance of the beams allows for large-amplitude in-plane oscillations in the direction parallel to the electrode while high axial stiffness prevents undesirable instabilities. The lumped model of the device, considered as an assembly of geometrically nonlinear massless flexures and a rigid massive link and built using the Rayleigh-Ritz method, predicted the feasibility of the excitation approach. The fabricated devices were operated in ambient air conditions by a combination of a steady (dc) and time-dependent (ac) components of voltage and the large-amplitude responses, up to 75 µm, in the vicinity of the principal parametric and primary resonances were registered by means of video acquisition and image processing. The shapes of the experimental resonant curves were consistent with those predicted by the model. The location and size of the instability regions on the frequency-voltage plane (parametric tongues) were quantitatively in good agrement with the model results. Theoretical and experimental results indicate that the suggested approach can be efficiently used for excitation of various types of microdevices where stable resonant operation combined with robustness and large vibrational amplitudes are desirable.

Krylov, Slava; Gerson, Yuval; Nachmias, Tali; Keren, Uri

2010-01-01

92

Modulated Amplitude Waves and the Transition from Phase to Defect Chaos  

CERN Multimedia

The mechanism for transitions from phase to defect chaos in the one-dimensional complex Ginzburg-Landau equation (CGLE) is presented. We introduce and describe periodic coherent structures of the CGLE, called Modulated Amplitude Waves (MAWs). MAWs of various period P occur naturally in phase chaotic states. A bifurcation study of the MAWs reveals that for sufficiently large period P, pairs of MAWs cease to exist via a saddle-node bifurcation. For periods beyond this bifurcation, incoherent near-MAW structures occur which evolve toward defects. This leads to our main result: the transition from phase to defect chaos takes place when the periods of MAWs in phase chaos are driven beyond their saddle-node bifurcation.

Brusch, L; Van Hecke, M; Baer, M E; Torcini, A; Brusch, Lutz; Zimmermann, Martin; Hecke, Martin van; Baer, Markus; Torcini, Alessandro

2000-01-01

93

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

Directory of Open Access Journals (Sweden)

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

K. Allali; M. Belhaq

2013-01-01

94

Stimulated light pressure on atoms in counterpropagating amplitude-modulated waves  

International Nuclear Information System (INIS)

Theoretical and experimental investigations were made of the effect of a stimulated light pressure on a beam of Na atoms. Expressions were obtained for the force exerted by this pressure on a two-level atom in the field of counterpropagating short light pulses of arbitrary area and also for the coefficient of pulsed diffusion of atoms in the case of square-wave light pulses. It was found that the value of this force close to the ideal case of square-wave pulses can be achieved in the case of counterpropagating amplitude-modulated waves, i.e., two standing waves of different frequencies, which is more convenient from the point of view of experimental implementation. An experimental study was made of the effects of a light pressure force in the field of two standing waves exerted on Na atoms in a beam.

1991-01-01

95

Decoding Finger Flexion using amplitude modulation from band-specific ECoG  

CERN Document Server

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

Liang, Nanying

2009-01-01

96

Amplitude sine modulated magnetic structures of DyPtGe{sub 2}  

Energy Technology Data Exchange (ETDEWEB)

Low temperature neutron diffraction has been performed on polycrystalline DyPtGe{sub 2}. The compound crystallizes in space group Immm; structural parameters have been refined for T = 30 K. A magnetic phase transition into an incommensurate antiferromagnetic structure with propagation vector [0.495, 0, 0] is observed to occur at 14({+-}1) K. At 5({+-}1) K the propagation vector becomes [0.268, 0, 0] and the amplitude sine modulated structure changes from a nearly transverse to a longitudinal type. The ordered Dy moments are 8.5 {+-} 0.4 {mu}{sub B} and 9.9 {+-} 0.5 {mu}{sub B} at 8 K and 4 K, respectively. (orig.) 5 refs.

Papathanassiou, G.; Kotsanidis, P.A.; Yakinthos, J.K. [Democritus Univ. of Thrace, Xanthi (Greece). Dept. of Electrical Engineering; Schaefer, W. [Bonn Univ. (Germany). Neutron Diffraction Group

1998-04-01

97

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; Gulliver T. Aaron

2005-01-01

98

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; Gulliver T Aaron

2005-01-01

99

EEG amplitude modulation analysis for semi-automated diagnosis of Alzheimer's disease  

Science.gov (United States)

Recent experimental evidence has suggested a neuromodulatory deficit in Alzheimer's disease (AD). In this paper, we present a new electroencephalogram (EEG) based metric to quantitatively characterize neuromodulatory activity. More specifically, the short-term EEG amplitude modulation rate-of-change (i.e., modulation frequency) is computed for five EEG subband signals. To test the performance of the proposed metric, a classification task was performed on a database of 32 participants partitioned into three groups of approximately equal size: healthy controls, patients diagnosed with mild AD, and those with moderate-to-severe AD. To gauge the benefits of the proposed metric, performance results were compared with those obtained using EEG spectral peak parameters which were recently shown to outperform other conventional EEG measures. Using a simple feature selection algorithm based on area-under-the-curve maximization and a support vector machine classifier, the proposed parameters resulted in accuracy gains, relative to spectral peak parameters, of 21.3% when discriminating between the three groups and by 50% when mild and moderate-to-severe groups were merged into one. The preliminary findings reported herein provide promising insights that automated tools may be developed to assist physicians in very early diagnosis of AD as well as provide researchers with a tool to automatically characterize cross-frequency interactions and their changes with disease.

Falk, Tiago H.; Fraga, Francisco J.; Trambaiolli, Lucas; Anghinah, Renato

2012-12-01

100

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

1991-01-01

 
 
 
 
101

Slow amplitude modulation in the pulse train of a self-mode-locked Ti:sapphire laser  

Energy Technology Data Exchange (ETDEWEB)

Periodic pulse-train amplitude modulations have been observed in a Kerr-lens self-mode-locked Ti:sapphire laser when the size of an intracavity slit is reduced below its optimal value for stable model locking. These transient processes are dominated by 100--500 kHz periodic pulse-energy modulations and are inherent to the Kerr-lens mode-locking mechanism based on the intensity dependent transverse-beam profile of the laser and the long gain relaxation lifetime (3.2 [mu]s) of the Ti:sapphire rod. They observe that when the slit width is decreased from 2 mm to 1.4 mm the modulation period increases from 2 [mu]s to 10 [mu]s and amplitude modulation deepens to almost 100%. An explanation similar to repetitive self-Q-switching and undamped relaxation oscillation is presented, which is consistent with the experimental results. A large low-frequency timing jitter on the order of submicroseconds, associated with the periodic pulse-train modulations, is also observed. The timing jitter is analyzed by incorporating the pulse-energy modulation into the phase variation through the Kerr effect and consistent results are obtained. They have determined the cavity parameters to control these detrimental processes for stable mode-locked output. The observation of the amplitude modulation further confirms the Kerr-lens self-focusing model of self-model locking in Ti:sapphire lasers.

Liu, Yan Ming; Prucnal, P.R. (Princeton Univ., NJ (United States). Advanced Technology Center for Photonics and Optoelectronic Materials)

1993-10-01

102

Effect of amplitude modulated RF radiation on calcium ion efflux and ODC activity in chronically exposed rat brain  

International Nuclear Information System (INIS)

The effect of exposing rats to amplitude modulated radiofrequency radiation (112 MHz modulated to 16 Hz) during development and growth has been examined. Wistar rats (35 days old) when exposed at above frequency at the power level 1.0 mW/cm2 (SAR, 0.75 W/kg) for 35 days showed enhanced ornithine decarboxylase activity and Ca2+ efflux in brain indicating potential health hazards due to exposure. (author)

1999-01-01

103

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; Wieckowski, Marcin

2011-01-01

104

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; Wieckowski, Marcin

2011-01-01

105

Reconfigurable optical quadrature amplitude modulation converter/encoder using a tunable complex coefficient optical tapped delay line.  

UK PubMed Central (United Kingdom)

We experimentally demonstrate a reconfigurable optical converter/encoder for quadrature amplitude modulated (QAM) signals. The system utilizes nonlinear wavelength multicasting, conversion-dispersion delays, and simultaneous nonlinear multiplexing and sampling. We show baud rate tunability (31 and 20 Gbaud) and reconfigurable conversions from lower-order QAM signals to higher-order QAM signals (e.g., 64-QAM).

Khaleghi S; Chitgarha MR; Yilmaz OF; Tur M; Haney MW; Langrock C; Fejer MM; Willner AE

2013-05-01

106

Reconfigurable optical quadrature amplitude modulation converter/encoder using a tunable complex coefficient optical tapped delay line.  

Science.gov (United States)

We experimentally demonstrate a reconfigurable optical converter/encoder for quadrature amplitude modulated (QAM) signals. The system utilizes nonlinear wavelength multicasting, conversion-dispersion delays, and simultaneous nonlinear multiplexing and sampling. We show baud rate tunability (31 and 20 Gbaud) and reconfigurable conversions from lower-order QAM signals to higher-order QAM signals (e.g., 64-QAM). PMID:23938882

Khaleghi, Salman; Chitgarha, Mohammad Reza; Yilmaz, Omer F; Tur, Moshe; Haney, Michael W; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

2013-05-15

107

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

UK PubMed Central (United Kingdom)

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.

Ren SL; Heremans JJ; Gaspe CK; Vijeyaragunathan S; Mishima TD; Santos MB

2013-10-01

108

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

2013-10-04

109

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

UK PubMed Central (United Kingdom)

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.

Vieira S; Ribeiro L; Jesus B; Cartaxana P; da Silva JM

2013-01-01

110

Amplitude modulation of sexy phrases is salient for song attractiveness in female canaries (Serinus canaria).  

UK PubMed Central (United Kingdom)

Song discrimination and recognition in songbird species have usually been studied by measuring responses to song playbacks. In female canaries, Serinus canaria, copulation solicitation displays (CSDs) are used as an index of female preferences, which are related to song recognition. Despite the fact that many studies underline the role of song syntax in this species, we observed that short segments of songs (a few seconds long) are enough for females to discriminate between conspecific and heterospecific songs, whereas such a short duration is not sufficient to identify the syntax rules. This suggests that other cues are salient for song recognition. In this experiment, we investigated the influence of amplitude modulation (AM) on the responses (CSDs) of female canaries to song playbacks. We used two groups of females: (1) raised in acoustic isolation and (2) raised in normal conditions. When adult, we tested their preferences for sexy phrases with different AMs. We broadcast three types of stimuli: (1) songs with natural canary AM, (2) songs with AM removed, or (3) song with wren Troglodytes troglodytes AM. Results indicate that female canaries prefer and have predispositions for a song type with the natural canary AM. Thus, this acoustic parameter is a salient cue for song attractiveness.

Pasteau M; Ung D; Kreutzer M; Aubin T

2012-07-01

111

Phase retrieval via spatial light modulator phase modulation in 4f optical setup: numerical inverse imaging with sparse regularization for phase and amplitude.  

Science.gov (United States)

The 4f optical setup is considered with a wave field modulation by a spatial light modulator located in the focal plane of the first lens. Phase as well as amplitude of the wave field are reconstructed from noisy multiple-intensity observations. The reconstruction is optimal due to a constrained maximum likelihood formulation of the problem. The proposed algorithm is iterative with decoupling of the inverse of the forward propagation of the wave field and the filtering of phase and amplitude. The sparse modeling of phase and amplitude enables the advanced high-accuracy filtering and sharp imaging of the complex-valued wave field. Artifacts typical for the conventional algorithms (wiggles, ringing, waves, etc.) and attributed to optical diffraction can be suppressed by the proposed algorithm. PMID:22218357

Katkovnik, Vladimir; Astola, Jaakko

2012-01-01

112

Phase retrieval via spatial light modulator phase modulation in 4f optical setup: numerical inverse imaging with sparse regularization for phase and amplitude.  

UK PubMed Central (United Kingdom)

The 4f optical setup is considered with a wave field modulation by a spatial light modulator located in the focal plane of the first lens. Phase as well as amplitude of the wave field are reconstructed from noisy multiple-intensity observations. The reconstruction is optimal due to a constrained maximum likelihood formulation of the problem. The proposed algorithm is iterative with decoupling of the inverse of the forward propagation of the wave field and the filtering of phase and amplitude. The sparse modeling of phase and amplitude enables the advanced high-accuracy filtering and sharp imaging of the complex-valued wave field. Artifacts typical for the conventional algorithms (wiggles, ringing, waves, etc.) and attributed to optical diffraction can be suppressed by the proposed algorithm.

Katkovnik V; Astola J

2012-01-01

113

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

2013-06-15

114

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

UK PubMed Central (United Kingdom)

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?gUL(-1) after 5h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC50=142±98?gUL(-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.

Herlory O; Bonzom JM; Gilbin R

2013-09-01

115

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

International Nuclear Information System (INIS)

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

2002-12-12

116

Nonlinear Analysis of the Eckhaus Instability Modulated Amplitude Waves and Phase Chaos with Non-zero Average Phase Gradient  

CERN Multimedia

We analyze the Eckhaus instability of plane waves in the one-dimensional complex Ginzburg-Landau equation (CGLE) and describe the nonlinear effects arising in the Eckhaus unstable regime. Modulated amplitude waves (MAWs) are quasi-periodic solutions of the CGLE that emerge near the Eckhaus instability of plane waves and cease to exist due to saddle-node bifurcations (SN). These MAWs can be characterized by their average phase gradient $\

Brusch, L; Baer, M E; Brusch, Lutz; Torcini, Alessandro; Baer, Markus

2001-01-01

117

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

International Nuclear Information System (INIS)

[en] 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

1987-01-01

118

The membrane potential of characean cells exposed to amplitude-modulated, low-power 147-MHz radiation  

Energy Technology Data Exchange (ETDEWEB)

The membrane potential of isolated cells of Chara braunii or Nitella flexilis was monitored while the cells were exposed, at nominal power densities from 2 to 1,000 W/m2, to 147-MHz radiation amplitude modulated at frequencies from 4 to 64 Hz. Phase-sensitive detection was used to seek radiation-correlated changes in the membrane potential, and none were apparent under any of the conditions used in this investigation.

Brunkard, K.M.; Pickard, W.F.

1984-01-01

119

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

120

Modulating protein activity and cellular function by methionine residue oxidation.  

Science.gov (United States)

The sulfur-containing amino acid residue methionine (Met) in a peptide/protein is readily oxidized to methionine sulfoxide [Met(O)] by reactive oxygen species both in vitro and in vivo. Methionine residue oxidation by oxidants is found in an accumulating number of important proteins. Met sulfoxidation activates calcium/calmodulin-dependent protein kinase II and the large conductance calcium-activated potassium channels, delays inactivation of the Shaker potassium channel ShC/B and L-type voltage-dependent calcium channels. Sulfoxidation at critical Met residues inhibits fibrillation of atherosclerosis-related apolipoproteins and multiple neurodegenerative disease-related proteins, such as amyloid beta, ?-synuclein, prion, and others. Methionine residue oxidation is also correlated with marked changes in cellular activities. Controlled key methionine residue oxidation may be used as an oxi-genetics tool to dissect specific protein function in situ. PMID:22146868

Cui, Zong Jie; Han, Zong Qiang; Li, Zhi Ying

2011-12-07

 
 
 
 
121

Modulating protein activity and cellular function by methionine residue oxidation.  

UK PubMed Central (United Kingdom)

The sulfur-containing amino acid residue methionine (Met) in a peptide/protein is readily oxidized to methionine sulfoxide [Met(O)] by reactive oxygen species both in vitro and in vivo. Methionine residue oxidation by oxidants is found in an accumulating number of important proteins. Met sulfoxidation activates calcium/calmodulin-dependent protein kinase II and the large conductance calcium-activated potassium channels, delays inactivation of the Shaker potassium channel ShC/B and L-type voltage-dependent calcium channels. Sulfoxidation at critical Met residues inhibits fibrillation of atherosclerosis-related apolipoproteins and multiple neurodegenerative disease-related proteins, such as amyloid beta, ?-synuclein, prion, and others. Methionine residue oxidation is also correlated with marked changes in cellular activities. Controlled key methionine residue oxidation may be used as an oxi-genetics tool to dissect specific protein function in situ.

Cui ZJ; Han ZQ; Li ZY

2012-08-01

122

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

UK PubMed Central (United Kingdom)

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

Kuriki S; Kobayashi Y; Kobayashi T; Tanaka K; Uchikawa Y

2013-02-01

123

Homocysteine reduces NMDAR desensitization and differentially modulates peak amplitude of NMDAR currents, depending on GluN2 subunit composition.  

UK PubMed Central (United Kingdom)

N-methyl-d-aspartate receptors (NMDARs) have been linked to schizophrenia because agents that bind the receptor, like ketamine and phencyclidine, are capable of inducing schizophrenia-like symptoms. Here we show that the amino acid homocysteine (HCY), which is increased in the blood of schizophrenia patients, reduces desensitization of NMDARs in cultured mouse neurons, human embryonic kidney cells transfected with GluN1 + GluN2A, GluN2B, or GluN2D subunits, and hippocampal slices. HCY also alters the peak amplitude of NMDAR currents, depending on the GluN2 subunit the receptor contains; GluN1 + GluN2A-containing NMDARs show an increase in peak amplitude when exposed to HCY, while GluN1 + GluN2B-containing NMDARs show a decrease in peak amplitude. Both peak amplitude and desensitization effects of HCY can be occluded by saturating the NMDAR with glycine. Since glycine concentrations are not saturating in the brain, HCY could play an NMDAR-modulating role in the nervous system. We also show that HCY shares characteristics with glutamate and suggest that HCY affects both the agonist and co-agonist site of the NMDAR.

Bolton AD; Phillips MA; Constantine-Paton M

2013-10-01

124

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

2013-01-01

125

Composite Amplitude Modulated Phase Only Filter Based Detection and Tracking of the Back-Reflection of KDP Images  

Energy Technology Data Exchange (ETDEWEB)

An algorithm for determining the position of the KDP back-reflection image was developed. It was compared to a centroid-based algorithm. While the algorithm based on centroiding exhibited a radial standard deviation of 9 pixels, the newly proposed algorithm based on classical matched filtering (CMF) and a Gaussian fit to correlation peak provided a radial standard deviation of less than 1 pixel. The speed of the peak detection was improved from an average of 5.5 seconds for Gaussian fit to 0.022 seconds by using a polynomial fit. The performance was enhanced even further by utilizing a composite amplitude modulated phase only filter; producing a radial standard deviation of 0.27 pixels. The proposed technique was evaluated on 900+ images with varying degrees of noise and image amplitude as well as real National Ignition Facility (NIF) images.

Awwal, A S; McClay, W A; Ferguson, S W; Candy, J V; Salmon, J T; Wegner, P J

2004-08-26

126

Complex phase/amplitude spatial light modulator advances and use in a multispectral optical correlator  

Science.gov (United States)

Optical processing systems often require compact high frame rate spatial light modulators (SLMs), usually with application specific modulation requirements in the complex plane. In this paper we discuss several advances at Boulder Nonlinear Systems toward this goal, including our liquid crystal (LC) on VLSI 128 X 128 analog SLM, and our multispectral hybrid incoherent to coherent converter.We also present the analysis of optical modulation possibilities when utilizing zero twist nematic and planar aligned chiral smectic LC on a reflective backplane. Finally we present the design of a multispectral optical correlator for machine vision applications such as food inspection, security, or manufacturing inspection.

Bauchert, Kipp A.; Serati, Steven A.; Sharp, Gary D.; McKnight, Douglas J.

1997-03-01

127

Calcium modulates the frequency and amplitude of spontaneous otoacoustic emissions in the bobtail skink.  

UK PubMed Central (United Kingdom)

Active processes in the inner ear of lizards can be monitored using spontaneous otoacoustic emissions (SOAE) measured outside the eardrum. In the Australian bobtail lizard, SOAE are generated by an active motility process in the hair-cell bundle. This mechanism has been shown to be sensitive to the calcium-chelating agent 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and is presumed to be related to the calcium-sensitive transduction-channel motor implicated in other nonmammalian hair cell systems. In studies of frog saccular and turtle auditory papillar hair cells in vitro, the frequency and amplitude of bundle oscillations depend on the concentration of calcium in the bathing solutions. In the present study, the calcium concentration in the endolymph was changed in vivo in the Australian bobtail lizard Tiliqua rugosa, and SOAE were monitored. Glass pipettes with large tips and containing different calcium concentrations in their fluids were introduced into scala media, and their contents were allowed to passively flow into the endolymph. Low calcium concentrations resulted in a downward shift in the frequency of SOAE spectral peaks and generally an increase in their amplitudes. Calcium concentrations > 2 mM resulted in increases in frequency of SOAE peaks and generally a loss in amplitude. These frequency shifts were consistent with in vitro data on the frequencies and amplitudes of spontaneous oscillation of hair cell bundles and thus also implicate calcium ions in the generation of active motility in nonmammalian hair cells. The data also suggest that in this lizard species, the ionic calcium concentration in the cochlear endolymph is > or = 1 mM.

Manley GA; Sienknecht U; Köppl C

2004-11-01

128

Calcium modulates the frequency and amplitude of spontaneous otoacoustic emissions in the bobtail skink.  

Science.gov (United States)

Active processes in the inner ear of lizards can be monitored using spontaneous otoacoustic emissions (SOAE) measured outside the eardrum. In the Australian bobtail lizard, SOAE are generated by an active motility process in the hair-cell bundle. This mechanism has been shown to be sensitive to the calcium-chelating agent 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and is presumed to be related to the calcium-sensitive transduction-channel motor implicated in other nonmammalian hair cell systems. In studies of frog saccular and turtle auditory papillar hair cells in vitro, the frequency and amplitude of bundle oscillations depend on the concentration of calcium in the bathing solutions. In the present study, the calcium concentration in the endolymph was changed in vivo in the Australian bobtail lizard Tiliqua rugosa, and SOAE were monitored. Glass pipettes with large tips and containing different calcium concentrations in their fluids were introduced into scala media, and their contents were allowed to passively flow into the endolymph. Low calcium concentrations resulted in a downward shift in the frequency of SOAE spectral peaks and generally an increase in their amplitudes. Calcium concentrations > 2 mM resulted in increases in frequency of SOAE peaks and generally a loss in amplitude. These frequency shifts were consistent with in vitro data on the frequencies and amplitudes of spontaneous oscillation of hair cell bundles and thus also implicate calcium ions in the generation of active motility in nonmammalian hair cells. The data also suggest that in this lizard species, the ionic calcium concentration in the cochlear endolymph is > or = 1 mM. PMID:15102898

Manley, Geoffrey A; Sienknecht, Ulrike; Köppl, Christine

2004-04-21

129

Amplitude- versus frequency-modulated pumping light for coherent population trapping resonances at high buffer-gas pressure  

International Nuclear Information System (INIS)

[en] Coherent population trapping (CPT) signals can be optimized with amplitude-modulated pumping light. As shown theoretically and experimentally in this paper, the optimum wave forms produce strong CPT signals at both low buffer-gas pressures, where the hyperfine structure (HFS) splitting of the optical absorption lines is well resolved, and also at high buffer-gas pressures, where the HFS is no longer optically resolved due to pressure broadening. On the other hand, CPT resonances from frequency-modulated waves are severely degraded for these high-pressure conditions. High buffer-gas pressures may offer advantages for miniature frequency standards and magnetometers, including suppression of diffusion losses in miniature cells, suppression of light shifts, and less stringent requirements for frequency stability of the pumping light sources

2005-01-01

130

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.

Teodorescu Kinneret; Bouchigny Sylvain; Hoffmann Pablo; Korman Maria

2011-01-01

131

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

132

Achievement of longitudinally polarized focusing with long focal depth by amplitude modulation.  

UK PubMed Central (United Kingdom)

The longitudinal component of a focused beam is split into two parts along the optical axis to obtain a longitudinally polarized long focal depth using amplitude filtering based on Euler transformation and a radially polarized Bessel-Gaussian beam. Numerical results indicate that long focal depth and FWHM can be easily achieved with 9? and 0.8?, respectively. A radially polarized beam can be converted into a longitudinally polarized beam with a conversion efficiency of 51.0%. It can therefore be believed that the proposed scheme can be widely used to generate a longitudinally polarized beam for particle acceleration, laser cutting, and optical trapping.

Lin J; Yin K; Li Y; Tan J

2011-04-01

133

Achievement of longitudinally polarized focusing with long focal depth by amplitude modulation.  

Science.gov (United States)

The longitudinal component of a focused beam is split into two parts along the optical axis to obtain a longitudinally polarized long focal depth using amplitude filtering based on Euler transformation and a radially polarized Bessel-Gaussian beam. Numerical results indicate that long focal depth and FWHM can be easily achieved with 9? and 0.8?, respectively. A radially polarized beam can be converted into a longitudinally polarized beam with a conversion efficiency of 51.0%. It can therefore be believed that the proposed scheme can be widely used to generate a longitudinally polarized beam for particle acceleration, laser cutting, and optical trapping. PMID:21479024

Lin, Jie; Yin, Ke; Li, Yuda; Tan, Jiubin

2011-04-01

134

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

Science.gov (United States)

A PEG hydrogel has been imaged by AFM in amplitude and in frequency modulation mode.Images measured in frequency modulation mode clearly show nano-scale domains.Selected roughness parameters can be used as descriptors for spatial resolution.The roughness parameters need to be robust to variations in the topography tilt angle.

Munz, M.

2013-08-01

135

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

Science.gov (United States)

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

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

2012-10-01

136

Information retrieval from amplitude modulated fringe patterns using single frame processing methods  

Science.gov (United States)

Two single-image methods designed for a fringe image modulation extraction are described. They are based on the two dimensional continuous wavelet transformation (2D CWT) and two dimensional Hilbert transform (2D HT) aided by bidimensional empirical mode decomposition (BEMD). Optimization of the proposed methods is described. Numerical simulations designed to test their performance are presented. Both approaches applicability is verified by processing experimental resonance vibration patterns acquired using time-average interferometry. Obtained results agree well with ones obtained using temporal phase shifting method.

Patorski, Krzysztof; Pokorski, Krzysztof; Wielgus, Maciej

2011-09-01

137

Tip-Jump Response of an Amplitude-Modulated Atomic Force Microscope  

Directory of Open Access Journals (Sweden)

Full Text Available The dynamic behaviors of an Atomic Force Microscope are of interest, and variously unpredictable phenomena are experimentally measured. In practical measurements, researchers have proposed many methods for avoiding these uncertainties. However, causes of these phenomena are still hard to demonstrate in simulation. To demonstrate these phenomena, this paper claims the tip-jump motion is a predictable process, and the jumping kinetic energy results in different nonlinear phenomena. It emphasizes the variation in the eigenvalues of an AFM with tip-sample distance. This requirement ensures the phase transformations from one associated with the oscillation mode to one associated with the tip-jump/sample-contact mode. Also, multi-modal analysis was utilized to ensure the modal transformation in varying tip-sample distances. In the presented model, oscillations with various tip-sample distances and with various excitation frequencies and amplitudes were compared. The results reveal that the tip-jump motion separates the oscillation orbit into two regions, and the jumping kinetic energy, comparing with the superficial potential energy, leads the oscillation to be bistable or intermittent. The sample-contact condition associates to bifurcation and chaos. Additionally, the jumping is a strong motion that occurrs before the tip-sample contacts, and this motion signal can replace the sample-contact-signal to avoid destroying the sample.

Po-Jen Shih

2012-01-01

138

Tighter focusing of amplitude modulated radially polarized vector beams in ultra-high numerical aperture lens systems  

Science.gov (United States)

Two kinds of amplitude apodization filters are proposed to modulate the radially polarized vector beam in ultra-high numerical aperture (NA) aplanatic lens systems in order to create a tighter focus. When focusing a radially polarized Bessel-Gaussian vector beam, we show the light spot at the focal plane is possible to be suppressed from 0.68? to 0.46? (32.4% sharper) with a dry objective lens of NA=0.95, and from 0.50? to 0.34? (32.0% sharper) with an oil immersion objective lens of NA=1.4, respectively; both surpass the Abbe's diffraction resolution limit of ?/(2NA). For a uniform radially polarized beam, the focal spot further sharpens.

Liu, Tao; Tan, Jiubin; Liu, Jian

2013-05-01

139

Intermittent exposures to nanoTesla range, 7 Hz, amplitude-modulated magnetic fields increase regeneration rates in planarian.  

UK PubMed Central (United Kingdom)

PURPOSE: To discern if physiologically and naturally-patterned electromagnetic fields presented with base frequencies of 7 Hz within the 100 nT range could facilitate regeneration in planarian similar to microTesla, 60 Hz fields. METHODS: In two separate experiments planarian were decapitated and exposed to either 140 or 400 nT peak amplitude-modulated 7 Hz magnetic fields for 6 min once per hour, 8 h per night for 5 days. Daily regeneration rates and movement velocities (cm/min) were measured. RESULTS: The planarian exposed to either intensity magnetic field exhibited faster regeneration of photoreceptors and auricles compared to sham field and reference groups. The magnetic field exposure accommodated 50% of the variance during the faster growth days. CONCLUSIONS: Naturally-patterned, intermittently-presented weaker electromagnetic fields may produce enhanced regeneration rates in flat worms similar to those observed for 60 Hz, higher intensity fields.

Gang N; Parker GH; Lafrenie RM; Persinger MA

2013-05-01

140

Analyses of wavelength- and polarization-division multiplexed transmission characteristics of optical quadrature-amplitude-modulation signals.  

UK PubMed Central (United Kingdom)

We theoretically study optical transmission characteristics of wavelength-division multiplexed (WDM) and polarization-multiplexed (POLMUX) signals using high-order optical quadrature-amplitude-modulation (QAM) formats up to 256. First, we conduct intensive computer simulations on bit-error rates (BERs) in WDM POLMUX QAM transmission systems and find maximum transmission distances under the influence of nonlinear impairments. Next, to elucidate the physics behind such nonlinear transmission characteristics, we calculate the distribution of constellation points for QAM signals as functions of the the launched power, the transmission distance, and the symbol rate. These results lead to a closed-form formula for BER of any QAM formats. From such formula, we derive simple laws that determine the maximum transmission distance and the optimum power as functions of the QAM order and the symbol rate. These laws can well explain the simulation results.

Kikuchi K

2011-09-01

 
 
 
 
141

An approximate nonlinear model for time gain compensation of amplitude modulated images of ultrasound contrast agent perfusion.  

UK PubMed Central (United Kingdom)

Microbubble ultrasound contrast agents allow blood perfusion to be imaged at the cost of an increased attenuation that is not properly handled by existing time gain compensation methods. An automatic TGC has been developed that is able to account for different microbubble concentrations. The technique is an extension of a previously tested approach for modeling the nonlinear dependence of microbubble backscattering upon insonating pressure. The proposed method involves modeling in amplitude of the nonlinear attenuation for both forward and backward propagation, and the solution is achieved through an approximation set to overestimate the attenuation. The resulting equations are used to model and compensate amplitude modulation (AM) images; they are tested on radiofrequency data acquired using a clinical scanner from a gelatin tissue-mimicking phantom submerged in a contrast agent solution in the 0.08 MI to 0.51 MI range at 2 MHz. The nonlinear estimation equation presented here provides a significantly improved amplification profile compared with standard TGC algorithms, resulting in more accurate attenuation correction of the AM image.

Mari J; Hibbs K; Stride E; Eckersley R; Tang M

2010-04-01

142

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

143

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 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 Transientes (EOAT) e PEAEE, com ruído branco de amplitude modulada. RESULTADOS: para o exame de PEAEE, sugere-se que a intensidade ideal para o ponto de corte seja 50 dB (more) 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 Federal University of Pernambuco. RESULTS: for the auditory steady state response, it is suggested that the cut point intensity related with normal hearing is 50 dB SPL, as it was (more) 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.

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

2012-06-01

144

Amyloid formation in denatured single-mutant lysozymes where residual structures are modulated.  

UK PubMed Central (United Kingdom)

Reduced hen lysozyme has a residual structure involving long-range interaction. It has been demonstrated that a single mutation (A9G, W62G, W111G, or W123G) in the residual structure differently modulates the long-range interactions of reduced lysozyme. To examine whether such variations in the residual structure affect amyloid formation, reduced and alkylated mutant lysozymes were incubated under the amyloid-fibrillation condition. From the analyses of CD spectra and thioflavine T fluorescences, it was suggested that variation in residual structure led to different amyloid formation. Interestingly, the extent of amyloid formation did not always correlate with the extent to which the residual structure was maintained, resulting in the involvement of a hydrophobic cluster normally contained in W111 in the reduced lysozyme.

Mishima T; Ohkuri T; Monji A; Imoto T; Ueda T

2006-10-01

145

Amyloid formation in denatured single-mutant lysozymes where residual structures are modulated.  

Science.gov (United States)

Reduced hen lysozyme has a residual structure involving long-range interaction. It has been demonstrated that a single mutation (A9G, W62G, W111G, or W123G) in the residual structure differently modulates the long-range interactions of reduced lysozyme. To examine whether such variations in the residual structure affect amyloid formation, reduced and alkylated mutant lysozymes were incubated under the amyloid-fibrillation condition. From the analyses of CD spectra and thioflavine T fluorescences, it was suggested that variation in residual structure led to different amyloid formation. Interestingly, the extent of amyloid formation did not always correlate with the extent to which the residual structure was maintained, resulting in the involvement of a hydrophobic cluster normally contained in W111 in the reduced lysozyme. PMID:16963644

Mishima, Tomonori; Ohkuri, Takatoshi; Monji, Akira; Imoto, Taiji; Ueda, Tadashi

2006-09-08

146

Amplitude-modulated acoustic radiation force experienced by elastic and viscoelastic spherical shells in progressive waves.  

Science.gov (United States)

The dynamic acoustic radiation force resulting from a dual-frequency beam incident on spherical shells immersed in an inviscid fluid is examined theoretically in relation to their thickness and the contents of their interior hollow regions. The theory is modified to include a hysteresis type of absorption inside the shells' material. The results of numerical calculations are presented for stainless steel and absorbing lucite (PolyMethyMethacrylAte) shells with the hollow region filled with water or air. Significant differences occur when the interior fluid inside the hollow region is changed from water to air. It is shown that the dynamic radiation force function Yd deviates from the static radiation force function Yp when the modulation size parameter deltax = mid R:x2 - x1mid R: (x1 = k1a, x2 = k2a, k1 and k2 are the wave vectors of the incident ultrasound waves, and a is the outer radius of the shell) starts to exceed the width of the resonance peaks in the Yp curves. PMID:16677678

Mitri, F G; Fellah, Z E A

2006-04-18

147

Method to improve the signal-to-noise ratio of photon-counting chirped amplitude modulation ladar.  

UK PubMed Central (United Kingdom)

Photon-counting chirped amplitude modulation (PCCAM) ladar employs Geiger mode avalanche photodiode as a detector. After the detector corresponding to the echo signal is reflected from an object or target, the modulation depth (MD) of the detection outputs has some certain loss relative to that of the transmitting signal. The signal-to-noise ratio (SNR) of PCCAM ladar is mainly determined by the MD of detection outputs of the echo signal. There is a proper echo signal intensity that can decrease the MD loss and improve the SNR of the ladar receiver. In this paper, an improved PCCAM ladar system is presented, which employs an echo signal intensity optimization strategy with an iris diaphragm under different signal and noise intensities. The improved system is demonstrated with the background noise of a sunny day and the echo signal intensity from 0.1 to 10 counts/ns. The experimental results show that it can effectively improve the SNR of the ladar receiver compared with the typical PCCAM ladar system.

Zhang Z; Wu L; Zhang Y; Zhao Y

2013-01-01

148

Noisy Galvanic Vestibular Stimulation Modulates the Amplitude of EEG Synchrony Patterns  

Science.gov (United States)

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

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

2013-01-01

149

A modeling study of the responses of the lateral superior olive to ipsilateral sinusoidally amplitude-modulated tones.  

UK PubMed Central (United Kingdom)

The lateral superior olive (LSO) is a brainstem nucleus that is classically understood to encode binaural information in high-frequency sounds. Previous studies have shown that LSO cells are sensitive to envelope interaural time difference in sinusoidally amplitude-modulated (SAM) tones (Joris and Yin, J Neurophysiol 73:1043-1062, 1995; Joris, J Neurophysiol 76:2137-2156, 1996) and that a subpopulation of LSO neurons exhibit low-threshold potassium currents mediated by Kv1 channels (Barnes-Davies et al., Eur J Neurosci 19:325-333, 2004). It has also been shown that in many LSO cells the average response rate to ipsilateral SAM tones decreases with modulation frequency above a few hundred Hertz (Joris and Yin, J Neurophysiol 79:253-269, 1998). This low-pass feature is not directly inherited from the inputs to the LSO since the response rate of these input neurons changes little with increasing modulation frequency. In the current study, an LSO cell model is developed to investigate mechanisms consistent with the responses described above, notably the emergent rate decrease with increasing frequency. The mechanisms explored included the effects of after-hyperpolarization (AHP) channels, the dynamics of low-threshold potassium channels (KLT), and the effects of background inhibition. In the model, AHP channels alone were not sufficient to induce the observed rate decrease at high modulation frequencies. The model also suggests that the background inhibition alone, possibly from the medial nucleus of the trapezoid body, can account for the small rate decrease seen in some LSO neurons, but could not explain the large rate decrease seen in other LSO neurons at high modulation frequencies. In contrast, both the small and large rate decreases were replicated when KLT channels were included in the LSO neuron model. These results support the conclusion that KLT channels may play a major role in the large rate decreases seen in some units and that background inhibition may be a contributing factor, a factor that could be adequate for small decreases.

Wang L; Colburn HS

2012-04-01

150

Effects of weak microwave fields amplitude modulated at ELF on EEG of symmetric brain areas in rats  

Energy Technology Data Exchange (ETDEWEB)

Averaged electroencephalogram (EEG) frequency spectra were studied in eight unanesthetized and unmyorelaxed adult male rats with chronically implanted carbon electrodes in symmetrical somesthetic areas when a weak microwave field, amplitude-modulated at extremely low frequency (ELF) was applied. Intermittent field exposure was used. Hemispheric asymmetry in frequency spectra of an ongoing EEG was characterized by a power decrease in the 1.5--3 Hz range on the left hemisphere and by a power decrease in the 10--14 and 20--30 Hz ranges on the right hemisphere. No differences between control and exposure experiments were shown under these routines of data averaging. Significant elevations of EEG asymmetry in 10--14 Hz range were observed during the first 20 s after four from five onsets of the MW field, when averaged spectra were obtained for every 10 s. Under neither control nor pre- and post-exposure conditions was this effect observed. These results are discussed with respect to interaction of MW fields with the EEG generators.

Vorobyov, V.V.; Galchenko, A.A.; Kukushkin, N.I.; Akoev, I.G. [Russian Academy of Science, Pushchino (Russian Federation). Inst. of Cell Biophysics

1997-06-01

151

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

Energy Technology Data Exchange (ETDEWEB)

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.

Nony, Laurent; Bocquet, Franck; Loppacher, Christian [Aix-Marseille Universite, IM2NP, Centre Scientifique de Saint-Jerome, Avenue Escadrille Normandie-Niemen, Case 151, F-13397 Marseille Cedex 20 (France); Glatzel, Thilo [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)], E-mail: laurent.nony@im2np.fr

2009-07-01

152

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)

[en] 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.

2009-07-01

153

Alanine-scanning mutagenesis in the signature disulfide loop of the glycine receptor alpha 1 subunit: critical residues for activation and modulation.  

Science.gov (United States)

The glycine receptor enables the generation of inhibitory postsynaptic currents at synapses via neurotransmitter-dependent activation. These receptors belong to the ligand-gated ion channel gene superfamily, in which all members are comprised of five subunits, each of which possesses a signature 13-residue disulfide loop (Cys loop) in the extracellular domain. In this study, we used alanine-scanning mutagenesis of the residues between C138 and C152 of the Cys loop of the glycine receptor alpha1 subunit to identify residues critical for receptor activation and allosteric modulation. Mutation of L142, F145, or P146 to alanine produced decreases in the potency, maximal amplitude, and Hill coefficient for currents elicited by glycine and impaired receptor activation by the agonist taurine. These residues, along with D148, are positionally conserved in the family of LGIC subunits. Mutation at several other positions had little or no effect. The inhaled anesthetics halothane and isoflurane potentiate submaximal agonist responses at wild-type receptors, via an allosteric site. The mutations L142A, F145A, P146A, and D148A abolished positive modulation by these anesthetics, in some cases revealing a small inhibitory effect. A molecular model of the glycine receptor alpha1 subunit suggests that the Cys loop is positioned in a region of the receptor at the interface between the extracellular and transmembrane domains and that the critical functional residues identified here lie along the face of a predominantly hydrophobic surface. The present data implicate the Cys loop as an important functional moiety in the process of glycine receptor activation and allosteric regulation by anesthetics. PMID:15287733

Schofield, Claude M; Trudell, James R; Harrison, Neil L

2004-08-10

154

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

Science.gov (United States)

We investigated the ionic mechanisms that allow dynamic regulation of action potential (AP) amplitude as a means of regulating energetic costs of AP signaling. Weakly electric fish generate an electric organ discharge (EOD) by summing the APs of their electric organ cells (electrocytes). Some electric fish increase AP amplitude during active periods or social interactions and decrease AP amplitude when inactive, regulated by melanocortin peptide hormones. This modulates signal amplitude and conserves energy. The gymnotiform Eigenmannia virescens generates EODs at frequencies that can exceed 500 Hz, which is energetically challenging. We examined how E. virescens meets that challenge. E. virescens electrocytes exhibit a voltage-gated Na(+) current (I(Na)) with extremely rapid recovery from inactivation (?(recov) = 0.3 ms) allowing complete recovery of Na(+) current between APs even in fish with the highest EOD frequencies. Electrocytes also possess an inwardly rectifying K(+) current and a Na(+)-activated K(+) current (I(KNa)), the latter not yet identified in any gymnotiform species. In vitro application of melanocortins increases electrocyte AP amplitude and the magnitudes of all three currents, but increased I(KNa) is a function of enhanced Na(+) influx. Numerical simulations suggest that changing I(Na) magnitude produces corresponding changes in AP amplitude and that K(Na) channels increase AP energy efficiency (10-30% less Na(+) influx/AP) over model cells with only voltage-gated K(+) channels. These findings suggest the possibility that E. virescens reduces the energetic demands of high-frequency APs through rapidly recovering Na(+) channels and the novel use of KNa channels to maximize AP amplitude at a given Na(+) conductance. PMID:23324315

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

2013-01-16

155

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

UK PubMed Central (United Kingdom)

We investigated the ionic mechanisms that allow dynamic regulation of action potential (AP) amplitude as a means of regulating energetic costs of AP signaling. Weakly electric fish generate an electric organ discharge (EOD) by summing the APs of their electric organ cells (electrocytes). Some electric fish increase AP amplitude during active periods or social interactions and decrease AP amplitude when inactive, regulated by melanocortin peptide hormones. This modulates signal amplitude and conserves energy. The gymnotiform Eigenmannia virescens generates EODs at frequencies that can exceed 500 Hz, which is energetically challenging. We examined how E. virescens meets that challenge. E. virescens electrocytes exhibit a voltage-gated Na(+) current (I(Na)) with extremely rapid recovery from inactivation (?(recov) = 0.3 ms) allowing complete recovery of Na(+) current between APs even in fish with the highest EOD frequencies. Electrocytes also possess an inwardly rectifying K(+) current and a Na(+)-activated K(+) current (I(KNa)), the latter not yet identified in any gymnotiform species. In vitro application of melanocortins increases electrocyte AP amplitude and the magnitudes of all three currents, but increased I(KNa) is a function of enhanced Na(+) influx. Numerical simulations suggest that changing I(Na) magnitude produces corresponding changes in AP amplitude and that K(Na) channels increase AP energy efficiency (10-30% less Na(+) influx/AP) over model cells with only voltage-gated K(+) channels. These findings suggest the possibility that E. virescens reduces the energetic demands of high-frequency APs through rapidly recovering Na(+) channels and the novel use of KNa channels to maximize AP amplitude at a given Na(+) conductance.

Markham MR; Kaczmarek LK; Zakon HH

2013-04-01

156

Modulation of K11-linkage formation by variable loop residues within UbcH5A.  

Science.gov (United States)

Ubiquitination refers to the covalent addition of ubiquitin (Ub) to substrate proteins or other Ub molecules via the sequential action of three enzymes (E1, E2, and E3). Recent advances in mass spectrometry proteomics have made it possible to identify and quantify Ub linkages in biochemical and cellular systems. We used these tools to probe the mechanisms controlling linkage specificity for UbcH5A. UbcH5A is a promiscuous E2 enzyme with an innate preference for forming polyubiquitin chains through lysine 11 (K11), lysine 48 (K48), and lysine 63 (K63) of Ub. We present the crystal structure of a noncovalent complex between Ub and UbcH5A. This structure reveals an interaction between the Ub surface flanking K11 and residues adjacent to the E2 catalytic cysteine and suggests a possible role for this surface in formation of K11 linkages. Structure-guided mutagenesis, in vitro ubiquitination and quantitative mass spectrometry have been used to characterize the ability of residues in the vicinity of the E2 active site to direct synthesis of K11- and K63-linked polyubiquitin. Mutation of critical residues in the interface modulated the linkage specificity of UbcH5A, resulting in generation of more K63-linked chains at the expense of K11-linkage synthesis. This study provides direct evidence that the linkage specificity of E2 enzymes may be altered through active-site mutagenesis. PMID:21396940

Bosanac, Ivan; Phu, Lilian; Pan, Borlan; Zilberleyb, Inna; Maurer, Brigitte; Dixit, Vishva M; Hymowitz, Sarah G; Kirkpatrick, Donald S

2011-03-10

157

Modulation of K11-linkage formation by variable loop residues within UbcH5A.  

UK PubMed Central (United Kingdom)

Ubiquitination refers to the covalent addition of ubiquitin (Ub) to substrate proteins or other Ub molecules via the sequential action of three enzymes (E1, E2, and E3). Recent advances in mass spectrometry proteomics have made it possible to identify and quantify Ub linkages in biochemical and cellular systems. We used these tools to probe the mechanisms controlling linkage specificity for UbcH5A. UbcH5A is a promiscuous E2 enzyme with an innate preference for forming polyubiquitin chains through lysine 11 (K11), lysine 48 (K48), and lysine 63 (K63) of Ub. We present the crystal structure of a noncovalent complex between Ub and UbcH5A. This structure reveals an interaction between the Ub surface flanking K11 and residues adjacent to the E2 catalytic cysteine and suggests a possible role for this surface in formation of K11 linkages. Structure-guided mutagenesis, in vitro ubiquitination and quantitative mass spectrometry have been used to characterize the ability of residues in the vicinity of the E2 active site to direct synthesis of K11- and K63-linked polyubiquitin. Mutation of critical residues in the interface modulated the linkage specificity of UbcH5A, resulting in generation of more K63-linked chains at the expense of K11-linkage synthesis. This study provides direct evidence that the linkage specificity of E2 enzymes may be altered through active-site mutagenesis.

Bosanac I; Phu L; Pan B; Zilberleyb I; Maurer B; Dixit VM; Hymowitz SG; Kirkpatrick DS

2011-05-01

158

Modulating LOV domain photodynamics with a residue alteration outside the chromophore binding site.  

UK PubMed Central (United Kingdom)

Phototropins, a class of light-activated protein kinases, are essential for several blue light responses in plants and algae, including phototropism. These proteins contain two internal light, oxygen, and voltage sensitive (LOV) domains, which bind flavin chromophores and undergo a reversible photochemical formation of a cysteinyl-flavin adduct as part of the light sensing process. While the photodynamic properties of such photosensory domains are dictated by interactions between the chromophore and surrounding protein, more distant residues can play a significant role as well. Here we explore the role of the Phe434 residue in the photosensory response of the second LOV domain of Avena sativa phototropin 1 (AsLOV2), a model photochemical system for these LOV domains. Phe434 is more than 6 Å from the FMN chromophore in AsLOV2; nevertheless, an F434Y point mutation is likely to change several structural features of the chromophore binding site, as we demonstrate using molecular dynamics simulations. Transient absorption signals spanning 15 decades in time were compared for wild-type AsLOV2 and the F434Y mutant, showing that the latter has significantly altered photodynamics, including (i) a faster intersystem crossing leading to triplet formation on a nanosecond time scale, (ii) biphasic formation of adduct-state kinetics on the microsecond time scale, and (iii) greatly accelerated ground-state recovery kinetics on a second time scale. We present mechanistic models that link these spectroscopic differences to changes in the configuration of the critical cysteine residue and in the chromophore's accessibility to solvent and oxygen according to MD trajectories and purging experiments. Taken together, these results demonstrate the importance of residues outside the chromophore-binding pocket in modulating LOV domain photodynamics.

Song SH; Freddolino PL; Nash AI; Carroll EC; Schulten K; Gardner KH; Larsen DS

2011-04-01

159

The modulation of planetary wave propagation by the tropical QBO zonal winds and the associated effects in the residual meridional circulation  

Energy Technology Data Exchange (ETDEWEB)

The planetary wave-mean flow interactions during the different stage of the QBO are studied with the quasigeostrophic zonally-averaged mean flow equations and the linearized primitive equations for planetary waves. In the linear case of steady flows, there is no feedback between the mean flow and the planetary waves. The difference of dissipating planetary wave propagation between easterly and westerly phases of the QBO is confined chiefly to low latitudes. The results also show that the differences of planetary wave amplitudes with easterly phase minus westerly phase display dipole pattern in the northern hemisphere with increasing values at high latitudes. The residual circulation indicates that there is a slightly stronger poleward and downward transport at high latitudes caused by planetary wave propagation during easterly than westerly phases of the QBO. In the case of coupling between the planetary waves and the mean flow, a noticeable difference of planetary wave propagation emerges clearly at middle and high latitudes with obviously larger upward and equatorward EP fluxes in the easterly phase winter than in the westerly phase winter. By modulating the propagation of planetary waves, the tropical QBO introduces significant variabilities of the planetary wave amplitudes and the residual circulation in the northern hemisphere. The amplitudes of planetary waves are shown to be greater during the easterly phase winter than during the westerly phase winter; the advective transport due to planetary waves is enhanced and the difference between these two winters becomes more evident at middle and high latitudes comparing with the linear result. 55 refs.

Chen Wen; Huang Ronghui (Academia Sinica, Beijing, BJ (China). Inst. of Atmospheric Physics)

1999-05-01

160

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

Science.gov (United States)

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

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

2013-10-01

 
 
 
 
161

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

Science.gov (United States)

Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This 'constant maximum' protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of ABIs may benefit from using pulse rates greater than those presently used in most ABIs, and by sound processing strategies that enhance the modulation depth of the electrical stimulus while preserving dynamic range. PMID:23928683

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

2013-08-08

162

Modified hybrid subcarrier/amplitude/ phase/polarization LDPC-coded modulation for 400 Gb/s optical transmission and beyond.  

UK PubMed Central (United Kingdom)

In this paper, we present a modified coded hybrid subcarrier/ amplitude/phase/polarization (H-SAPP) modulation scheme as a technique capable of achieving beyond 400 Gb/s single-channel transmission over optical channels. The modified H-SAPP scheme profits from the available resources in addition to geometry to increase the bandwidth efficiency of the transmission system, and so increases the aggregate rate of the system. In this report we present the modified H-SAPP scheme and focus on an example that allows 11 bits/Symbol that can achieve 440 Gb/s transmission using components of 50 Giga Symbol/s (GS/s).

Batshon HG; Djordjevic I; Xu L; Wang T

2010-06-01

163

Modified hybrid subcarrier/amplitude/ phase/polarization LDPC-coded modulation for 400 Gb/s optical transmission and beyond.  

Science.gov (United States)

In this paper, we present a modified coded hybrid subcarrier/ amplitude/phase/polarization (H-SAPP) modulation scheme as a technique capable of achieving beyond 400 Gb/s single-channel transmission over optical channels. The modified H-SAPP scheme profits from the available resources in addition to geometry to increase the bandwidth efficiency of the transmission system, and so increases the aggregate rate of the system. In this report we present the modified H-SAPP scheme and focus on an example that allows 11 bits/Symbol that can achieve 440 Gb/s transmission using components of 50 Giga Symbol/s (GS/s). PMID:20588543

Batshon, Hussam G; Djordjevic, Ivan; Xu, Lei; Wang, Ting

2010-06-21

164

100 MHz Amplitude and Polarization Modulated Optical Source for Free-Space Quantum Key Distribution at 850 nm  

CERN Multimedia

We report on an integrated photonic transmitter of up to 100 MHz repetition rate, which emits pulses centered at 850 nm with arbitrary amplitude and polarization. The source is suitable for free space quantum key distribution applications. The whole transmitter, with the optical and electronic components integrated, has reduced size and power consumption. In addition, the optoelectronic components forming the transmitter can be space-qualified, making it suitable for satellite and future space missions.

Jofre, M; Anzolin, G; Molina-Terriza, G; Torres, J P; Mitchell, M W; Pruneri, V; 10.1109/JLT.2010.2056673

2010-01-01

165

Performance of UWB Systems with Direct-Sequence Bipolar Pulse Amplitude Modulation and RAKE Reception over IEEE 802.15.3a Channel  

Directory of Open Access Journals (Sweden)

Full Text Available Direct-Sequence Pulse Amplitude Modulation (DS-PAM) has been widely proposed for Ultra-Wideband (UWB) communication systems because it provides better performance with low computational complexity. UWB signals suffer from severe multi-path interference when employed in indoor fading environments. But using RAKE reception can make use of the rich multi-path of UWB systems to improve system performance. In this paper we present the performance of a RAKE receiver employing maximal ratio combining (MRC) in a DS UWB system with BPAM modulation. Performance in a practical multi-path fading Channel (IEEE 802.15.3a Channel) is considered to analyze the performance of DS-PAM UWB systems with different RAKE receivers. The bit error rate (BER) of ARake, PRake, and SRake over DS-BPAM UWB systems is simulated. The results indicate that ARake has the best performance, SRake is better than PRake when the number of fingers is the same.

Jingjing Wang; Hao Zhang

2011-01-01

166

Simultaneous subchannel data updating for multiple channels of 16-quadrature amplitude modulation signals using a single periodically poled lithium niobate waveguide.  

UK PubMed Central (United Kingdom)

Subchannel data updating of high-order modulation format signals using cascaded sum- and difference-frequency generation in a single periodically poled lithium niobate waveguide is demonstrated. One quadrature phase-shift-keying subchannel of a 16-quadrature amplitude modulation (QAM) signal at 40 Gbit/s is successfully updated, with an optical signal-to-noise ratio (OSNR) penalty of ~2 dB for return-to-zero and ~4 dB for non-return-to-zero at a bit-error rate (BER) of 2×10(-3). Simultaneous processing of four wavelength-multiplexed 16-QAM signals with an average OSNR penalty of 4.5 dB at a BER of 2×10(-3) is also demonstrated.

Huang H; Yang JY; Wu X; Khaleghi S; Ziyadi M; Tur M; Langrock C; Fejer MM; Paraschis L; Willner AE

2012-11-01

167

Simultaneous subchannel data updating for multiple channels of 16-quadrature amplitude modulation signals using a single periodically poled lithium niobate waveguide.  

Science.gov (United States)

Subchannel data updating of high-order modulation format signals using cascaded sum- and difference-frequency generation in a single periodically poled lithium niobate waveguide is demonstrated. One quadrature phase-shift-keying subchannel of a 16-quadrature amplitude modulation (QAM) signal at 40 Gbit/s is successfully updated, with an optical signal-to-noise ratio (OSNR) penalty of ~2 dB for return-to-zero and ~4 dB for non-return-to-zero at a bit-error rate (BER) of 2×10(-3). Simultaneous processing of four wavelength-multiplexed 16-QAM signals with an average OSNR penalty of 4.5 dB at a BER of 2×10(-3) is also demonstrated. PMID:23114297

Huang, Hao; Yang, Jeng-Yuan; Wu, Xiaoxia; Khaleghi, Salman; Ziyadi, Morteza; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Paraschis, Loukas; Willner, Alan E

2012-11-01

168

Scanning Tunneling Microscopy in TTF-TCNQ direct proof of phase and amplitude modulated charge density waves  

CERN Document Server

Charge density waves (CDW) have been studied at the surface of a cleaved TTF-TCNQ single crystal using a low temperature scanning tunneling microscope (STM) under ultra high vacuum (UHV) conditions. All CDW phase transitions of TTF-TCNQ have been identified. The measurement of the modulation wave vector along the a direction provides the first evidence for the existence of domains comprising single plane wave modulated structures in the temperature regime where the transverse wave vector of the CDW is temperature dependent, as hinted by the theory more than 20 years ago.

Wang, Z Z Z; Girard, J C; Pasquier, C; Bechgaard, K; Wang, Zhao Z.Z.; Jerome, Denis; Girard, Jean Christophe; Pasquier, Claude; Bechgaard, Klaus

2003-01-01

169

Investigation of the feasibility of amplitude-modulated dipolar decoupling in magic-angle spinning solid-state nuclear magnetic resonance  

International Nuclear Information System (INIS)

The feasibility of using periodic amplitude-modulated radio-frequency (RF) irradiation under 'magic-angle spinning' for heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance is addressed. The RF waveforms used are tailored to satisfy the theoretical criterion for decoupling which calls for an irradiated spin propagator which is cyclic in the sense that it equals the identity matrix irrespective of the strength and orientation of the chemical shift and dipolar coupling tensors. This requirement is met by using the Floquet formalism to provide insight into the influence of an arbitrary waveform on the dynamics of the irradiated spin-1/2 nuclei and invoking perturbation methods to design particular modulation functions which impose the required cyclicity on the propagator. Simple RF modulations which are synchronized with the sample spinning are thus derived analytically. Finally, the validity of the scheme is explored in simple test experiments and the decoupling performance is compared with the traditional 'continuous-wave' method and the recently developed technique of 'two-pulse phase modulation'. (author)

2000-09-14

170

A power matrix and control strategy that allows low THD and WHD for pulse width and amplitude modulated inverters  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the topology for an inverter power matrix and its corresponding control strategy. Due to the type of control proposed, the output waveform will provide a train of M number of pulses per half cycle whose width and amplitude evaluated at each pulse center are both proportional to the sinusoidal function. The proposed technique allows a relatively low THD and WHD to be generated. This paper shows how the THD and WHD can be reduced by introducing a correction factor in the quarter cycle centered pulse (M/2th pulse). Theoretical and computer simulation results for particular cases are included.

Macera, J.; Teshome, A. [Wichita State Univ., KS (United States). Dept. of Electrical Engineering

1996-11-01

171

Effects of Residual Dispersion on Intra-Channel Cross-Phase Modulation Induced Phase Fluctuation in Dispersion Managed Line  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of residual dispersion on intra-channel cross-phase modulation (IXPM) induced phase perturbation in optical RZ pulse propagating in a periodically dispersion managed (DM) transmission line are investigated in this work. Using perturbed variational formulation, we have obtained several or...

Nitu Syed; Tanjib Rubaiyat; Md Taosif Anowar

172

Amplitude modulated chirp excitation to reduce grating lobes and maintain ultrasound intensity at the focus of an array.  

UK PubMed Central (United Kingdom)

During application of high intensity focused ultrasound (HIFU) with therapy arrays, the existence of grating lobes can cause heating at unintended tissue regions. Therefore, the reduction of grating lobes in therapeutic arrays is an important goal. One way to reduce the grating lobes in therapy arrays is to excite the arrays with broadband signals (defined here as >10% fractional bandwidth). To achieve a reduction in grating lobe levels in an ultrasonic array, coded waveforms can be utilized that reduce the grating lobe levels while maintaining the spatial peak temporal average intensity. In this study, a 5-MHz, 9-element, 1.25 mm inter-elemental spacing linear array was excited by a sinusoidal waveform, a conventional linear chirp, and a modified linear chirp. Both chirps spanned the -3-dB bandwidth of the transducer. The conventional chirp was a broadband signal with a linear sweep of frequencies between 2.5 and 7.5 MHz, with all frequency components excited with equal amplitude. The modified chirp signal also swept the frequencies between 2.5 and 7.5 MHz, but the amplitude was weighted such that the edges (low and high frequencies of the band) were excited with more energy than the center of the band. In simulations, the field patterns for the sinusoidal, conventional chirp and modified chirp excitations were produced from the array using Field II and compared. For experiments, the beam pattern from a 5-MHz single-element transducer was mapped using a hydrophone for the sinusoidal, conventional chirp and modified chirp excitation. Each field from the transducer was repeated and summed to produce a field from an array of 9 elements. The difference in the time averaged intensity (in dB) in the main lobe and grating lobes were estimated for each excitation and compared. The results demonstrated that the chirp signals resulted in decreases in grating lobe levels compared to the main lobe, i.e. 10 dB down for focusing and 6 dB down for focusing and steering. A further 1 dB decrease in grating lobe levels was observed for the modified chirp excitation compared to the conventional chirp excitation, which corresponds to ~21% reduction in energy deposition at the grating lobe location.

Karunakaran CP; Oelze ML

2013-09-01

173

Novel configuration of finite-impulse-response filters tolerant to carrier-phase fluctuations in digital coherent optical receivers for higher-order quadrature amplitude modulation signals.  

UK PubMed Central (United Kingdom)

We propose a novel configuration of the finite-impulse-response (FIR) filter adapted by the phase-dependent decision-directed least-mean-square (DD-LMS) algorithm in digital coherent optical receivers. Since fast carrier-phase fluctuations are removed from the error signal which updates tap coefficients of the FIR filter, we can achieve stable adaptation of filter-tap coefficients for higher-order quadrature-amplitude modulation (QAM) signals. Computer simulations show that our proposed scheme is much more tolerant to the phase noise and the frequency offset than the conventional DD-LMS scheme. Such theoretical predictions are also validated experimentally by using a 10-Gsymbol/s dual-polarization 16-QAM signal.

Mori Y; Zhang C; Kikuchi K

2012-11-01

174

Novel configuration of finite-impulse-response filters tolerant to carrier-phase fluctuations in digital coherent optical receivers for higher-order quadrature amplitude modulation signals.  

Science.gov (United States)

We propose a novel configuration of the finite-impulse-response (FIR) filter adapted by the phase-dependent decision-directed least-mean-square (DD-LMS) algorithm in digital coherent optical receivers. Since fast carrier-phase fluctuations are removed from the error signal which updates tap coefficients of the FIR filter, we can achieve stable adaptation of filter-tap coefficients for higher-order quadrature-amplitude modulation (QAM) signals. Computer simulations show that our proposed scheme is much more tolerant to the phase noise and the frequency offset than the conventional DD-LMS scheme. Such theoretical predictions are also validated experimentally by using a 10-Gsymbol/s dual-polarization 16-QAM signal. PMID:23187478

Mori, Yojiro; Zhang, Chao; Kikuchi, Kazuro

2012-11-19

175

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

176

Scattering Amplitudes  

CERN Multimedia

The purpose of this review is to bridge the gap between a standard course in quantum field theory and recent fascinating developments in the studies of on-shell scattering amplitudes. We build up the subject from basic quantum field theory, starting with Feynman rules for simple processes in Yukawa theory and QED. The material covered includes spinor helicity formalism, on-shell recursion relations, superamplitudes and their symmetries, twistors and momentum twistors, loops and integrands, Grassmannians, polytopes, and amplitudes in perturbative supergravity as well as 3d Chern-Simons-matter theories. Multiple examples and exercises are included.

Elvang, Henriette

2013-01-01

177

Analysis and design of RF power and data link using amplitude modulation of Class-E for a novel bone conduction implant.  

Science.gov (United States)

This paper presents analysis and design of a radio frequency power and data link for a novel Bone Conduction Implant (BCI) system. Patients with conductive and mixed hearing loss and single-sided deafness can be rehabilitated by bone-anchored hearing aids (BAHA). Whereas the conventional hearing aids transmit sound to the tympanic membrane via air conduction, the BAHA transmits sound via vibrations through the skull directly to the cochlea. It uses a titanium screw that penetrates the skin and needs life-long daily care; it may cause skin infection and redness. The BCI is developed as an alternative to the percutaneous BAHA since it leaves the skin intact. The BCI comprises an external audio processor with a transmitter coil and an implanted unit called the bridging bone conductor with a receiver coil. Using amplitude modulation of the Class-E power amplifier that drives the inductive link, the sound signal is transmitted to the implant through the intact skin. It was found that the BCI can generate enough output force level for candidate patients. Maximum power output of the BCI was designed to occur at 5-mm skin thickness and the variability was within 1.5 dB for 1-8-mm skin thickness variations. PMID:22907959

Taghavi, Hamidreza; Håkansson, Bo; Reinfeldt, Sabine

2012-08-15

178

Analysis and design of RF power and data link using amplitude modulation of Class-E for a novel bone conduction implant.  

UK PubMed Central (United Kingdom)

This paper presents analysis and design of a radio frequency power and data link for a novel Bone Conduction Implant (BCI) system. Patients with conductive and mixed hearing loss and single-sided deafness can be rehabilitated by bone-anchored hearing aids (BAHA). Whereas the conventional hearing aids transmit sound to the tympanic membrane via air conduction, the BAHA transmits sound via vibrations through the skull directly to the cochlea. It uses a titanium screw that penetrates the skin and needs life-long daily care; it may cause skin infection and redness. The BCI is developed as an alternative to the percutaneous BAHA since it leaves the skin intact. The BCI comprises an external audio processor with a transmitter coil and an implanted unit called the bridging bone conductor with a receiver coil. Using amplitude modulation of the Class-E power amplifier that drives the inductive link, the sound signal is transmitted to the implant through the intact skin. It was found that the BCI can generate enough output force level for candidate patients. Maximum power output of the BCI was designed to occur at 5-mm skin thickness and the variability was within 1.5 dB for 1-8-mm skin thickness variations.

Taghavi H; Håkansson B; Reinfeldt S

2012-11-01

179

Application of fast amplitude-modulated pulse trains for signal enhancement in static and magic-angle-spinning 47,49Ti-NMR spectra.  

UK PubMed Central (United Kingdom)

It is demonstrated that the use of fast amplitude-modulated RF pulse trains with constant (FAM-I) and incremented pulse durations (SW-FAM) leads to considerable sensitivity enhancement for the central-transition signal (via spin population transfer from the satellite transitions) for solid-state NMR spectra of titanium, 47Ti (I = [Formula: see text] and 49Ti (I = [Formula: see text]. For the magic-angle spinning spectra of TiO2 and BaTiO3, the intensity of the 49Ti central-transition line was more than doubled compared to simple Hahn-echo acquisition, while for the static case, enhancement factors of 1.6 (TiO2) and 1.8 (BaTiO3) were obtained. No lineshape distortions are observed in either MAS or static spectra of both compounds. Employment of the FAM and SW-FAM sequences should be useful in the routine acquisition of 47,49Ti spectra, as the NMR signal can be detected much faster.

Bräuniger T; Madhu PK; Pampel A; Reichert D

2004-11-01

180

Application of fast amplitude-modulated pulse trains for signal enhancement in static and magic-angle-spinning 47,49Ti-NMR spectra.  

Science.gov (United States)

It is demonstrated that the use of fast amplitude-modulated RF pulse trains with constant (FAM-I) and incremented pulse durations (SW-FAM) leads to considerable sensitivity enhancement for the central-transition signal (via spin population transfer from the satellite transitions) for solid-state NMR spectra of titanium, 47Ti (I = [Formula: see text] and 49Ti (I = [Formula: see text]. For the magic-angle spinning spectra of TiO2 and BaTiO3, the intensity of the 49Ti central-transition line was more than doubled compared to simple Hahn-echo acquisition, while for the static case, enhancement factors of 1.6 (TiO2) and 1.8 (BaTiO3) were obtained. No lineshape distortions are observed in either MAS or static spectra of both compounds. Employment of the FAM and SW-FAM sequences should be useful in the routine acquisition of 47,49Ti spectra, as the NMR signal can be detected much faster. PMID:15388175

Bräuniger, Thomas; Madhu, P K; Pampel, André; Reichert, Detlef

 
 
 
 
181

Amplitude Control: Closing the Loop  

Science.gov (United States)

We are using a compensated zero-path-difference Michelson interferometer to control optical amplitude and phase for application to the correction of optical errors in telescopes. Two spatial light modulators are used in place of the usual mirrors in the Michelson. The spatial light modulators are 128x128 pixel arrays from Boulder Nonlinear Systems. We have previously shown how this device can be used for amplitude control using laser and white-light sources. In this study we will present results of closing the loop around this device with the purpose of making an incident optical field uniform in amplitude. This work is supported by NASA and Princeton University.

Littman, M. G.; Carr, M.; Kasdin, J.; Vanderbei, R.; Spergel, D.

2002-12-01

182

Conserved Residues in Lassa Fever Virus Z Protein Modulate Viral Infectivity at the Level of the Ribonucleoprotein?  

Science.gov (United States)

Arenaviruses are negative-strand RNA viruses that cause human diseases such as lymphocytic choriomeningitis, Bolivian hemorrhagic fever, and Lassa hemorrhagic fever. No licensed vaccines exist, and current treatment is limited to ribavirin. The prototypic arenavirus, lymphocytic choriomeningitis virus (LCMV), is a model for dissecting virus-host interactions in persistent and acute disease. The RING finger protein Z has been identified as the driving force of arenaviral budding and acts as the viral matrix protein. While residues in Z required for viral budding have been described, residues that govern the Z matrix function(s) have yet to be fully elucidated. Because this matrix function is integral to viral assembly, we reasoned that this would be reflected in sequence conservation. Using sequence alignment, we identified several conserved residues in Z outside the RING and late domains. Nine residues were each mutated to alanine in Lassa fever virus Z. All of the mutations affected the expression of an LCMV minigenome and the infectivity of virus-like particles, but to greatly varying degrees. Interestingly, no mutations appeared to affect Z-mediated budding or association with viral GP. Our findings provide direct experimental evidence supporting a role for Z in the modulation of the activity of the viral ribonucleoprotein (RNP) complex and its packaging into mature infectious viral particles.

Capul, Althea A.; de la Torre, Juan Carlos; Buchmeier, Michael J.

2011-01-01

183

Modulation of the enzymatic activity of papain by interdomain residues remote from the active site.  

UK PubMed Central (United Kingdom)

The two main catalytic residues Cys25 and His159 of the monomeric cysteine protease papain are located on different walls of a cleft formed by two domains. This topology suggests a possible relationship between relative domain organization and catalytic mechanism. The effect on enzymatic parameters of structural modifications at various locations of the two-domain interface of papain was examined by individual or double replacements by Ala of pairs of interacting residues. Most modifications had no effect on enzyme activity. However, the enzyme's substrate turnover (kcat) decreased following simultaneous alteration of the two most conserved residues, forming an apolar contact located 15 A away from the active site. The pH activity profile of the double mutant was unchanged, indicating a conserved ionization state of the active site thiolate-imidazolium ion pair. This state is strongly dependent on the distance separating the two residues, thus suggesting that the active site geometry has not been significantly altered. Efficient enzymatic activity in papain requires more than a correct active site geometry and is influenced by domain packing properties in a region remote from the active site.

Altschuh D; Tessier DC; Vernet T

1994-06-01

184

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 e...

Li Bin; Gallin Warren J

185

Effects of Residual Dispersion on Intra-Channel Cross-Phase Modulation Induced Phase Fluctuation in Dispersion Managed Line  

Directory of Open Access Journals (Sweden)

Full Text Available The effects of residual dispersion on intra-channel cross-phase modulation (IXPM) induced phase perturbation in optical RZ pulse propagating in a periodically dispersion managed (DM) transmission line are investigated in this work. Using perturbed variational formulation, we have obtained several ordinary differential equations for various pulse parameters. These equations have been solved to identify phase perturbation in the DM cell of the system. Full numerical simulation of the nonlinear Schrodinger equation has been employed to identify effects of nonlinear phase fluctuation on pulse propagation and to investigate the intra-pulse interaction. The analytical result is verified by numerical simulation based on split-step Fourier method (SSFM). We therefore explore the effects of various parameters such as transmission distance, input power, duty cycle, and bit-rate on phase fluctuation for different single channel transmission models. Simulation results confirm significant improvement in the phase fluctuations due to IXPM by using dispersion managed line having some residual dispersion compared to perfect dispersion compensation. The outcome of our work is to explore the performance of the DM system with respect to some residual dispersion so that the IXPM induced phase fluctuations remain low.

Nitu Syed; Tanjib Rubaiyat; Md Taosif Anowar

2013-01-01

186

Conserved residue modulates copper-binding properties through structural dynamics in human copper chaperone Atox1.  

UK PubMed Central (United Kingdom)

The human copper chaperone Atox1 plays a central role in the transport of copper in cells. It has been reported that the conserved residue Lys60 contributes to the heterocomplex stability of Atox1 with its target protein ATPase, and that the K60A mutation could diminish the copper transfer. In this work, we carried out the structure determination and dynamic analysis of Atox1 with the K60A mutation in order to elucidate the role of the conserved residue Lys60 in the copper transport. Results show that the K60A mutation results in crucial secondary structure rearrangements and side-chain orientation alteration of the metal-binding residues in Atox1. Protein dynamic studies reveal that the K60A mutation leads to increased overall flexibility, and a significant difference in dynamic properties of the metal-binding sites. The structure and dynamic changes cause a decrease in the copper-binding stability of the K60A mutant. In addition, Cu(i)-mediated hetero-protein interactions with ATP7A are present in the metal transfer of both Atox1 variants, although copper transfer is accompanied with smaller structural alteration in the K60A mutant. These results indicate that Lys60 is crucial in maintaining the structure and dynamic properties of Atox1.

Xi Z; Shi C; Tian C; Liu Y

2013-09-01

187

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

Directory of Open Access Journals (Sweden)

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

Li Bin; Gallin Warren J

2005-01-01

188

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

CERN Document Server

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

Danilov, G S

2003-01-01

189

Neuropathic and inflammatory pain are modulated by tuberoinfundibular peptide of 39 residues.  

Science.gov (United States)

Nociceptive information is modulated by a large number of endogenous signaling agents that change over the course of recovery from injury. This plasticity makes understanding regulatory mechanisms involved in descending inhibition of pain scientifically and clinically important. Neurons that synthesize the neuropeptide TIP39 project to many areas that modulate nociceptive information. These areas are enriched in its receptor, the parathyroid hormone 2 receptor (PTH2R). We previously found that TIP39 affects several acute nociceptive responses, leading us to now investigate its potential role in chronic pain. Following nerve injury, both PTH2R and TIP39 knockout mice developed less tactile and thermal hypersensitivity than controls and returned to baseline sensory thresholds faster. Effects of hindpaw inflammatory injury were similarly decreased in knockout mice. Blockade of ?-2 adrenergic receptors increased the tactile and thermal sensitivity of apparently recovered knockout mice, returning it to levels of neuropathic controls. Mice with locus coeruleus (LC) area injection of lentivirus encoding a secreted PTH2R antagonist had a rapid, ?-2 reversible, apparent recovery from neuropathic injury similar to the knockout mice. Ablation of LC area glutamatergic neurons led to local PTH2R-ir loss, and barley lectin was transferred from local glutamatergic neurons to GABA interneurons that surround the LC. These results suggest that TIP39 signaling modulates sensory thresholds via effects on glutamatergic transmission to brainstem GABAergic interneurons that innervate noradrenergic neurons. TIP39's normal role may be to inhibit release of hypoalgesic amounts of norepinephrine during chronic pain. The neuropeptide may help maintain central sensitization, which could serve to enhance guarding behavior. PMID:23878240

Dimitrov, Eugene L; Kuo, Jonathan; Kohno, Kenji; Usdin, Ted B

2013-07-22

190

Modulation of human immunodeficiency virus type 1 protease autoprocessing by charge properties of surface residue 69.  

Science.gov (United States)

Mature, fully active human immunodeficiency virus protease (PR) is liberated from the Gag-Pol precursor via regulated autoprocessing. A chimeric protease precursor, glutathione S-transferase-transframe region (TFR)-PR-FLAG, also undergoes N-terminal autocatalytic maturation when it is expressed in Escherichia coli. Mutation of the surface residue H69 to glutamic acid, but not to several neutral or basic amino acids, impedes protease autoprocessing in bacteria and mammalian cells. Only a fraction of mature PR with an H69E mutation (PR(H69E)) folds into active enzymes, and it does so with an apparent Kd (dissociation constant) significantly higher than that of the wild-type protease, corroborating the marked retardation of the in vitro N-terminal autocatalytic processing of TFR-PR(H69E) and suggesting a folding defect in the precursor. PMID:19457992

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

2009-05-20

191

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

Science.gov (United States)

Mature, fully active human immunodeficiency virus protease (PR) is liberated from the Gag-Pol precursor via regulated autoprocessing. A chimeric protease precursor, glutathione S-transferase-transframe region (TFR)-PR-FLAG, also undergoes N-terminal autocatalytic maturation when it is expressed in Escherichia coli. Mutation of the surface residue H69 to glutamic acid, but not to several neutral or basic amino acids, impedes protease autoprocessing in bacteria and mammalian cells. Only a fraction of mature PR with an H69E mutation (PRH69E) folds into active enzymes, and it does so with an apparent Kd (dissociation constant) significantly higher than that of the wild-type protease, corroborating the marked retardation of the in vitro N-terminal autocatalytic processing of TFR-PRH69E and suggesting a folding defect in the precursor.

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

2009-01-01

192

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

International Nuclear Information System (INIS)

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

2003-02-01

193

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.

2012-01-01

194

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

195

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

196

Frequency dependence of a 633-nm He-Ne laser stabilized bby /sup 127/I/sub 2/, upon iodine pressure, modulation amplitude, and wall temperature  

Energy Technology Data Exchange (ETDEWEB)

The beat frequency of the frequency shifts of a 633 nm He-Ne laser (S) stabilized by intracavity saturated absorption to hyperfine components e and f of Iodine was measured. The reference laser (M) had an unheated iodine cell and an 18 C cold finger temperature. Half the observations were of S locked to iodine peak 2, M locked to f, and the rest with components interchanged. Linear frequency to pressure and frequency to modulation relations result, with the coefficients and extrapolated intercepts at zero pressure being dependent on the wall temperature. These relations are expressed in an empirical formula that enables the frequency correction to be calculated within + or - 5% for any deviation from standard operating parameters. (ESA)

Rowley, W.R.C.

1981-09-01

197

High-order rational harmonic mode-locking and pulse-amplitude equalization of SOAFL via reshaped gain-switching FPLD pulse injection.  

UK PubMed Central (United Kingdom)

The 40-GHz rational harmonic mode-locking (RHML) and pulse-amplitude equalization of a semiconductor optical amplifier based fiber-ring laser (SOAFL) is demonstrated by the injection of a reshaped 10-GHz gain-switching FPLD pulse. A nonlinearly biased Mach-Zehnder modulator (MZM) is employed to detune the shape of the double-peak pulse before injecting the SOA, such that a pulse-amplitude equalized 4th-order RHML-SOAFL can be achieved by reshaping the SOA gain within one modulation period. An optical injection mode-locking model is constructed to simulate the compensation of uneven amplitudes between adjacent RHML pulse peaks before and after pulse-amplitude equalization. The indirect gain compensation technique greatly suppresses the clock amplitude jitter from 45% to 3.5% when achieving 4th-order RHML, and the amplitude fluctuation of sub-rational harmonic modulating envelope is attenuated by 45 dB. After pulse-amplitude equalization, the pulsewidth of the optical-injection RHML-SOAFL is 8 ps, which still obeys the trend predicted by the inverse square root of repetition rate. The phase noise contributed by the residual ASE noise of the RHML-SOAFL is significantly decreased from -84 to -90 dBc/Hz after initiating the pulse-amplitude equalization, corresponding to the timing jitter reduction from 0.5 to 0.28 ps.

Lin GR; Kang JJ; Lee CK

2010-04-01

198

Diphoton generalized distribution amplitudes  

International Nuclear Information System (INIS)

We calculate the leading order diphoton generalized distribution amplitudes by calculating the amplitude of the process ?*???? in the low energy and high photon virtuality region at the Born order and in the leading logarithmic approximation. As in the case of the anomalous photon structure functions, the ?? generalized distribution amplitudes exhibit a characteristic lnQ2 behavior and obey inhomogeneous QCD evolution equations.

2008-08-01

199

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

UK PubMed Central (United Kingdom)

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.

Planells-Cases R; Ferrer-Montiel AV; Patten CD; Montal M

1995-09-01

200

Conformational change and human cytochrome c function: mutation of residue 41 modulates caspase activation and destabilizes Met-80 coordination.  

UK PubMed Central (United Kingdom)

Cytochrome c is a highly conserved protein, with 20 residues identical in all eukaryotic cytochromes c. Gly-41 is one of these invariant residues, and is the position of the only reported naturally occurring mutation in cytochrome c (human G41S). The basis, if any, for the conservation of Gly-41 is unknown. The mutation of Gly-41 to Ser enhances the apoptotic activity of cytochrome c without altering its role in mitochondrial electron transport. Here we have studied additional residue 41 variants and determined their effects on cytochrome c functions and conformation. A G41T mutation decreased the ability of cytochrome c to induce caspase activation and decreased the redox potential, whereas a G41A mutation had no impact on caspase induction but the redox potential increased. All residue 41 variants decreased the pK (a) of a structural transition of oxidized cytochrome c to the alkaline conformation, and this correlated with a destabilization of the interaction of Met-80 with the heme iron(III) at physiological pH. In reduced cytochrome c the G41T and G41S mutations had distinct effects on a network of hydrogen bonds involving Met-80, and in G41T the conformational mobility of two ?-loops was altered. These results suggest the impact of residue 41 on the conformation of cytochrome c influences its ability to act in both of its physiological roles, electron transport and caspase activation.

Josephs TM; Liptak MD; Hughes G; Lo A; Smith RM; Wilbanks SM; Bren KL; Ledgerwood EC

2013-03-01

 
 
 
 
201

Using a 1.2 GHz bandwidth reflective semiconductor optical amplifier with seeding light by 64-quadrature amplitude modulation orthogonal frequency division multiplexing modulation to achieve a 10-gbits/s upstream rate in long-reach passive optical network access  

Science.gov (United States)

We use a commercially available 1.2 GHz bandwidth reflective semiconductor optical amplifier (RSOA)--based optical network unit (ONU) to achieve 10-gbits/s upstream traffic for an optical orthogonal frequency division multiplexing (OFDM) long-reach passive optical network (LR-PON). This is the first time the 64--quadrature amplitude modulation (QAM) OFDM format has been applied to RSOA-ONU to achieve a 75 km fiber transmission length. In the proposed LR-PON, the upstream power penalty of 5.2 dB at the bit error rate of 3.8×10-3 is measured by using a 64-QAM OFDM modulation after the 75 km fiber transmission without dispersion compensation.

Yeh, Chien-Hung; Chen, Hsing-Yu; Chow, Chi-Wai; Wu, Yu-Fu

2012-01-01

202

Diphoton Generalized Distribution Amplitudes  

CERN Document Server

We calculate the leading order diphoton generalized distribution amplitude by calculating the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region at the Born order and in the leading logarithmic approximation. As in the case of the anomalous photon structure functions, the gamma gamma generalized distribution amplitude exhibits a characteristic \\ln Q^2 behaviour and obeys inhomogeneous evolution equations.

Beiyad, M El; Szymanowski, L; Wallon, S

2008-01-01

203

Amplitude-mode dynamics of polariton condensates.  

UK PubMed Central (United Kingdom)

We study the stability of collective amplitude excitations in nonequilibrium polariton condensates. These excitations correspond to renormalized upper polaritons and to the collective amplitude modes of atomic gases and superconductors. They would be present following a quantum quench or could be created directly by resonant excitation. We show that uniform amplitude excitations are unstable to the production of excitations at finite wave vectors, leading to the formation of density-modulated phases. The physical processes causing the instabilities can be understood by analogy to optical parametric oscillators and the atomic Bose supernova.

Brierley RT; Littlewood PB; Eastham PR

2011-07-01

204

Dose escalation by intensity-modulated radiotherapy boost after whole pelvic radiotherapy in postoperative patients of carcinoma cervix with residual disease.  

UK PubMed Central (United Kingdom)

AIMS: External beam radiotherapy followed by brachytherapy is the standard treatment for patients with carcinoma cervix. However, for patients who come from peripheral hospitals after incomplete surgery, whole pelvic radiotherapy (WPRT) followed by boost with either vaginal vault brachytherapy if suitable or further external beam radiotherapy is recommended. This study was conducted to evaluate if it was possible to give a higher tumour dose using intensity-modulated radiotherapy for that group of patients who were not suitable for high dose rate vaginal vault brachytherapy because of gross disease after WPRT. MATERIALS AND METHODS: A prospective study was carried out from 2005 to 2010 in which 25 postoperative patients of cervical carcinoma with gross residual disease after WPRT of 46 Gy/23 fractions/4.5 weeks were included. Nine patients were treated with 20 Gy to the planning target volume and 30 Gy to the clinical target volume in 10 fractions; 16 patients were treated with 30 Gy to the planning target volume and 35 Gy to the clinical target volume in 15 fractions. The end points of this study were local control, survival and treatment-related toxicity. RESULTS: The median follow-up was 38 months. The 3 year local control, progression-free survival and overall survival rates were 76, 74 and 67%, respectively. Late grade 2 rectal toxicity was seen in 11 patients. Grade 2 bladder toxicity occurred in two patients and grade 3 bowel toxicity in two patients. No other grade 3 or higher toxicity was seen. CONCLUSION: Inadequate and inappropriate surgery in invasive cervical cancer with resulting gross residual disease is common in India. It is possible to escalate the tumour dose by intensity-modulated radiotherapy boost after WPRT in postoperative cervical carcinoma patients with gross residual disease with low incidence of severe toxicity and excellent local control.

Khosla D; Patel FD; Rai B; Chakraborty S; Oinam AS; Sharma SC

2013-01-01

205

Approximate eikonal exchange amplitudes  

Energy Technology Data Exchange (ETDEWEB)

A first-order correction is presented to a previously derived zeroth-order approximate eikonal exchange amplitude for electron-hydrogen scattering and both the modulus and the phase are compared with those of the exact eikonal exchange amplitude for elastic scattering. The correction term dramatically improves the approximation, even at energies as low as 50 eV.

Halpern, A.M.; Franco, V.

1981-03-16

206

Two Photon Distribution Amplitudes  

CERN Multimedia

The factorization of the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region is demonstrated at the Born order and in the leading logarithmic approximation. The leading order two photon (generalized) distribution amplitudes exhibit a characteristic ln Q2 behaviour and obey new inhomogeneous evolution equations.

Beiyad, M El; Szymanowski, L; Wallon, S

2008-01-01

207

Two Photon Distribution Amplitudes  

International Nuclear Information System (INIS)

The factorization of the amplitude of the process ?*???? in the low energy and high photon virtuality region is demonstrated at the Born order and in the leading logarithmic approximation. The leading order two photon (generalized) distribution amplitudes exhibit a characteristic ln Q2 behaviour and obey new inhomogeneous evolution equations.

2008-08-29

208

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

209

Cell surface adhesion of pregnancy-associated plasma protein-A is mediated by four clusters of basic residues located in its third and fourth CCP module  

DEFF Research Database (Denmark)

The metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) cleaves a subset of insulin-like growth factor binding proteins (IGFBP), which inhibit the activities of insulin-like growth factor (IGF). Through this proteolytic activity, PAPP-A is believed to regulate IGF bioavailability in several biological systems, including the human reproductive system and the cardiovascular system. PAPP-A adheres to mammalian cells by interactions with glycosaminoglycan (GAG), thus targeting the proteolytic activity of PAPP-A to the cell surface. Based on site-directed mutagenesis, we here delineate the PAPP-A GAG-binding site in the C-terminal modules CCP3 and CCP4. Using heparin affinity chromatography, commonly employed in such studies, we define three clusters of arginines and lysines of CCP3, which are important for the interaction of PAPP-A with heparin. In a model of PAPP-A CCP3-CCP4, basic residues of these sequence clusters form a contiguous patch located on one side of the structure. Binding to the unknown, natural cell surface receptor of PAPP-A, assessed by flow cytometry, also depends on residues of these three basic clusters. However, single or double residue substitutions generally have a modest effect on PAPP-A heparin binding assessed by chromatography, but cell surface adhesion was critically reduced by several of these substitutions, emphasizing the relevance of analysis by flow cytometry. The contributions of positively charged residues located in CCP4 were all minor when analyzed by heparin affinity chromatography. However, the mutation of CCP4 residues Arg1459 and Lys1460 to Ala almost abrogated cell surface adhesion. Furthermore, when acidic residues of the homologous proteinase PAPP-A2 (Asp1547, Glu1555 and Glu1567) were introduced into the corresponding positions in the sequence of PAPP-A, located in each of the three basic clusters of CCP3, binding to heparin was strongly impaired and cell surface binding was abrogated. This explains, at least in part, why PAPP-A2 lacks the ability of cell surface adhesion, and further emphasizes the role of the basic clusters defined in PAPP-A.

Weyer, Kathrin; Overgaard, Michael Toft

2004-01-01

210

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

2011-01-27

211

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

UK PubMed Central (United Kingdom)

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.

Cockburn DW; Clarke AJ

2011-05-01

212

Reinforcing saccadic amplitude variability.  

UK PubMed Central (United Kingdom)

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 reinforced the least frequent saccadic amplitudes to increase variability, and then reinforced the central part of the amplitude distributions to reduce variability. The target was placed at a constant distance from the fovea after the saccade to maintain the postsaccadic visual signal constant and an auditory reinforcement was delivered depending on saccadic amplitude. The second experiment tested the effects of the contingency. We reinforced high levels of variability in 4 participants, whereas 4 other participants were assigned to a yoked control group. On average, saccadic amplitude standard deviations were doubled while the medians remained mostly unchanged in the experimental participants in both experiments, and variability returned to baseline level when low variability was reinforced. In the control group no consistent changes in amplitude distributions were observed. These results, showing that variability can be reinforced, challenge the idea of a stochastic neural noise. We instead propose that selection processes constrain saccadic amplitude distributions.

Paeye C; Madelain L

2011-03-01

213

The angiotensin II type 1 receptor C-terminal Lys residues interact with tubulin and modulate receptor export trafficking.  

UK PubMed Central (United Kingdom)

The physiological and pathological functions of angiotensin II are largely mediated through activating the cell surface angiotensin II type 1 receptor (AT1R). However, the molecular mechanisms underlying the transport of newly synthesized AT1R from the endoplasmic reticulum (ER) to the cell surface remain poorly defined. Here we demonstrated that the C-terminus (CT) of AT1R directly and strongly bound to tubulin and the binding domains were mapped to two consecutive Lys residues at positions 310 and 311 in the CT membrane-proximal region of AT1R and the acidic CT of tubulin, suggestive of essentially ionic interactions between AT1R and tubulin. Furthermore, mutation to disrupt tubulin binding dramatically inhibited the cell surface expression of AT1R, arrested AT1R in the ER, and attenuated AT1R-mediated signaling measured as ERK1/2 activation. These data demonstrate for the first time that specific Lys residues in the CT juxtamembrane region regulate the processing of AT1R through interacting with tubulin. These data also suggest an important role of the microtubule network in the cell surface transport of AT1R.

Zhang X; Wang H; Duvernay MT; Zhu S; Wu G

2013-01-01

214

The angiotensin II type 1 receptor C-terminal Lys residues interact with tubulin and modulate receptor export trafficking.  

Science.gov (United States)

The physiological and pathological functions of angiotensin II are largely mediated through activating the cell surface angiotensin II type 1 receptor (AT1R). However, the molecular mechanisms underlying the transport of newly synthesized AT1R from the endoplasmic reticulum (ER) to the cell surface remain poorly defined. Here we demonstrated that the C-terminus (CT) of AT1R directly and strongly bound to tubulin and the binding domains were mapped to two consecutive Lys residues at positions 310 and 311 in the CT membrane-proximal region of AT1R and the acidic CT of tubulin, suggestive of essentially ionic interactions between AT1R and tubulin. Furthermore, mutation to disrupt tubulin binding dramatically inhibited the cell surface expression of AT1R, arrested AT1R in the ER, and attenuated AT1R-mediated signaling measured as ERK1/2 activation. These data demonstrate for the first time that specific Lys residues in the CT juxtamembrane region regulate the processing of AT1R through interacting with tubulin. These data also suggest an important role of the microtubule network in the cell surface transport of AT1R. PMID:23451270

Zhang, Xiaoping; Wang, Hong; Duvernay, Matthew T; Zhu, Shu; Wu, Guangyu

2013-02-25

215

Finite amplitude envelope solitons  

International Nuclear Information System (INIS)

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

1977-01-01

216

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

UK PubMed Central (United Kingdom)

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

Kazmierczak M; Zhang X; Chen B; Mulkey DK; Shi Y; Wagner PG; Pivaroff-Ward K; Sassic JK; Bayliss DA; Jegla T

2013-06-01

217

Residue 19 of the parathyroid hormone (PTH) modulates ligand interaction with the juxtamembrane region of the PTH-1 receptor.  

UK PubMed Central (United Kingdom)

Recent data suggest that the binding of parathyroid hormone (PTH)-(1-34) to the PTH-1 receptor (P1R) involves a high-affinity interaction between the C-terminal (15-34) domain of the ligand and the amino-terminal extracellular (N) domain of the receptor and a low-affinity interaction between the N-terminal (1-14) portion of PTH and the juxtamembrane (J) region of the receptor, with the latter interaction giving rise to signal transduction. We investigated whether residues C-terminal of position 14 in PTH(1-34) contribute to the J component of the interaction mechanism by comparing the capacity of PTH analogues N-terminally modified to improve J domain affinity and C-terminally truncated at position 14, 20, or 34 to stimulate cAMP formation in COS-7 cells transiently transfected with P1R-delNt, a P1R construct that lacks most of the N domain. In these cells, the potency of [M]PTH(1-34) (M = Ala(1,3,12),Gln(10),Har(11),Trp(14),Arg(19)) was 120-fold greater than that of [M]PTH(1-14) (EC(50)s = 3.0 +/- 0.8 and 360 +/- 90 nM, respectively) but was equal to that of [M]PTH(1-20) (EC(50) = 2.3 +/- 0.3 nM). Reverting the Arg(19) substitution of [M]PTH(1-20) to the native Glu reduced cAMP signaling potency on P1R-delNt by 12-fold (EC(50) of [M]PTH(1-20)-Glu(19) = 27 +/- 4 nM), and it decreased the analog's capacity to inhibit the binding of the J domain-selective radioligand, (125)I-[Aib(1,3),Nle(8),M,Tyr(21)]ratPTH(1-21), to the full-length P1R stably expressed in LLC-PK1 cells by 40-fold. The Glu(19) --> Arg modification, however, did not affect the capacity of PTH(15-31) to inhibit the binding of the N domain-selective radioligand (125)I-bPTH(3-34) to the full-length receptor. The overall data suggest that residues (15-20) of PTH, and particularly residue 19, contribute to the capacity of the N-terminal portion of the ligand to interact with the juxtamembrane region of the receptor. The NMR data presented in the accompanying manuscript suggests that this role could involve intramolecular effects on secondary structure in the N-terminal portion of the ligand.

Shimizu M; Shimizu N; Tsang JC; Petroni BD; Khatri A; Potts JT Jr; Gardella TJ

2002-11-01

218

Eikonal exchange amplitudes  

Energy Technology Data Exchange (ETDEWEB)

We show that the existing and widely used results for an approximation to eikonal exchange amplitudes, which contain an indeterminate phase, are not valid. We derive a new analytic result, containing a well-defined phase, which can be used unambiguously with direct amplitudes to calculate full differential cross sections. The modulus of our result also differs from that of the previous formulations. Comparisons are made with the earlier e/sup -/-H approximate exchange calculations and with exact eikonal exchange calculations.

Franco, V.; Halpern, A.M.

1980-04-01

219

Quantum Mechanics without amplitudes  

CERN Multimedia

Amplitudes are the major logical object in Quantum Theory. Despite this fact they presents no physical reality and in consequence only observables can be experimetally checked. We discuss the possibility of a theory of Quantum Probabilities capable of give full account to quantum phenomena. Advanteges of this formulation are the evidence of physical processes not described by the orotodox formulation using amplitudes and the possibility of a full algoritimization of Quantum Mechanics.

Figueiredo, J M A

2004-01-01

220

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

International Nuclear Information System (INIS)

[en] Purpose: To estimate the dosimetric impact of residual setup errors on parotid sparing in head-and-neck (H and N) intensity-modulated treatments and to evaluate the effect of employing an PRV (planning organ-at-risk volume) margin for the parotid gland. Patients and methods: Ten patients treated for H and N cancer were considered. A nine-beam intensity-modulated radiotherapy (IMRT) was planned for each patient. A second optimization was performed prescribing dose constraint to the PRV of the parotid gland. Systematic setup errors of 2 mm, 3 mm, and 5 mm were simulated. The dose-volume histograms of the shifted and reference plans were compared with regard to mean parotid gland dose (MPD), normal-tissue complication probability (NTCP), and coverage of the clinical target volume (V95% and equivalent uniform dose [EUD]); the sensitivity of parotid sparing on setup error was evaluated with a probability-based approach. Results: MPD increased by 3.4%/mm and 3.0%/mm for displacements in the craniocaudal and lateral direction and by 0.7%/mm for displacements in the anterior-posterior direction. The probability to irradiate the parotid with a mean dose > 30 Gy was > 50%, for setup errors in cranial and lateral direction and 95% and EUD variations

2009-01-01

 
 
 
 
221

Detecting Pesticide Residue by Using Modulating Temperature Over a Single SnO2-Based Gas Sensor  

Directory of Open Access Journals (Sweden)

Full Text Available A new rapid detecting method (called dynamic measurements ) was reported to detect and distinguish the presence of two pesticide gases in the ambient atmosphere. The method employed only a single SnO2-based gas sensor in a rectangular temperature mode to perform the qualitative analysis of a binary gas mixture (acephate and trichlorphon) in air. Polar plots was used for quantitative analysis which the feature extraction was performed by FFT. Experimental results showed that high selectivity of the sensor achieved in the range of 250~3000C and modulating frequency 20mHz, one can easily observe the qualitative difference among the response to pure acephate and trichlorphon gases of the same concentration and to the mixture, and the concentration of pesticide gases can be obtained based on the changes of polar plots.

Xingjiu Huang; Jinhuai Liu; Zongxin Pi; Zengliang Yu

2003-01-01

222

A novel chromatic dispersion monitoring technique for 16/64-QAM system based on asynchronous amplitude histogram  

Science.gov (United States)

A novel chromatic dispersion (CD) monitoring technique based on asynchronous amplitude histogram (AAH) for higher order modulation formats is proposed in this paper. Without demodulating the signal, in the monitoring scheme, the received signal is sampled asynchronously, and thus clock information and high-speed sampling units are unnecessary, resulting in low cost and high reliability. Simulations of CD monitoring technique for non-return-to-zero/return-to-zero (NRZ/RZ) 16- and 64-quadrature amplitude modulation (QAM) systems with different optical signal-to-noise ratios (OSNRs) and duty cycles are investigated, and the tolerance of the scheme is also discussed. Simulation results show that the presented CD monitoring technique with high sensitivity can be applied to monitor the residual CD of a transmission link in the next-generation optical networks.

Yan, Li-juan; Zhu, Bo; Liu, Guo-qing; Hu, Fang-ren

2013-05-01

223

Fatigue Reliability under Multiple-Amplitude Loads  

DEFF Research Database (Denmark)

A method to determine the fatigue of structures subjected to multiple-amplitude loads is presented. Unlike the more common cumulative damage methods, which are usually based on fatigue life data, the proposed method is based on tensile strength data. Assuming the Weibull distribution for the initial tensile strength and the fatigue life, the probability distributions for the residual tensile strength in both the crack initiation and the crack propagation stages of fatigue are determined. The method is illustrated for two-amplitude loads by means of experimental results obtained by testing specimens of a structural steel and is shown to be more accurate than the Palmgren-Miner cumulative damage method.

Talreja, R.

1979-01-01

224

Seismic reflection amplitudes  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses seismic amplitude variations with offset contain information about the elastic parameters. Prestack amplitude analysis seeks to extract this information by using the variations of the reflection coefficients as functions of angle of incidence. Normally, an approximate formula is used for the reflection coefficients, and variations with offset of the geometrical spreading and the anelastic attenuation are often ignored. Using angle of incidence as the dependent variable is also computationally inefficient since the data are recorded as a function of offset. Improved approximations have been derived for the elastic reflection and transmission coefficients, the geometrical spreading and the complex travel-time (including anelastic attenuation). For a 1 D medium, these approximations are combined to produce seismic reflection amplitudes (P-wave, S-wave or converted wave) as a Taylor series in the offset coordinate. The coefficients of the Taylor series are computed directly from the parameters of the medium, without using the ray parameter.

Upsin, B. (Petroleum Center, N-7034 Trondheim NTH (NO)); Dahl, T. (Statoil Research Center, Postuttak, N-7004 Trondheim (NO))

1992-07-01

225

NATURE OF CYCLICAL CHANGES IN THE TIMING RESIDUALS FROM THE PULSAR B1642 - 03  

International Nuclear Information System (INIS)

[en] We report an analysis of timing data for the pulsar B1642-03 (J1645 - 0317) gathered over the 40-year time span between 1969 and 2008. During this interval, the pulsar experienced eight glitch-like events with a fractional increase in the rotation frequency ??/? ? (0.9-2.6) x 10-9. We have revealed two important relations in the properties of these peculiar glitches. The first result shows that there is a strong linear correlation between the amplitude of the glitch and the time interval to the next glitch with a slope of about 0.0026 x 10-9 Hz day-1. This relation allows us to predict epochs of new glitches. The second result shows that the amplitude of the glitches is modulated by a periodic large-scale sawtooth-like function. As a result of this modulation, the glitch amplitude varies discretely from glitch to glitch with a step of 1.5 x 10-9 Hz in the range (2.4-6.9) x 10-9 Hz. The post-glitch time interval also varies discretely with a step of ? 600 days in the range 900-2700 days. An analysis of the data showed that three modulation schemes with modulation periods of 43 years, 53 years, and 60 years are possible. The best model is the 60-year modulation scheme including 12 glitches. We make a conclusion that the nature of the observed cyclical changes in the timing residuals from PSR B1642 - 03 is a continuous generation of peculiar glitches whose amplitudes are modulated by a periodic large-scale sawtooth-like function. As the modulation function is periodical, the picture of cyclical timing residuals will be exactly repeated in each modulation period or every 60 years.

2009-08-01

226

Amplitude and Ascoli analysis  

International Nuclear Information System (INIS)

[en] 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.)

1976-01-01

227

Survey of Modulation Classification Methods for QAM Signals.  

Science.gov (United States)

Classification of the modulation type of a signal is a rapidly evolving research area with interests in both civilian and military applications. Quadrature Amplitude Modulation (QAM) is a modulation scheme where both the amplitude and phase of the signal ...

M. Wikstroem

2005-01-01

228

Delbrueck amplitudes: New calculations  

Energy Technology Data Exchange (ETDEWEB)

Calculations of the first-order Delbrueck scattering amplitudes were parallelized in a medium-grain mode assuring a very efficient, equal-load implementation, on systems with a moderate number of processors. New numerical values were calculated in the energy range 7.92-28 MeV and in the angular range 0.001deg-120deg with an estimated accuracy of as good as 1%. The old tables of Bar-Noy and Kahane are improved by these new calculations especially the values of Re A{sub +-} amplitudes. Good agreement is found with the calculations of Turrini, Maino and Ventura with a smoother behaviour of the present values. The calculations were performed on a system of eight transputers. (orig.).

Kahane, S. (Dept. of Physics, NEGEV Nuclear Research Centre, Beer Sheva (Israel))

1992-06-15

229

Delbrueck amplitudes: New calculations  

International Nuclear Information System (INIS)

Calculations of the first-order Delbrueck scattering amplitudes were parallelized in a medium-grain mode assuring a very efficient, equal-load implementation, on systems with a moderate number of processors. New numerical values were calculated in the energy range 7.92-28 MeV and in the angular range 0.001deg-120deg with an estimated accuracy of as good as 1%. The old tables of Bar-Noy and Kahane are improved by these new calculations especially the values of Re A+- amplitudes. Good agreement is found with the calculations of Turrini, Maino and Ventura with a smoother behaviour of the present values. The calculations were performed on a system of eight transputers. (orig.)

1992-06-15

230

Light Meson Distribution Amplitudes  

CERN Multimedia

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

231

Improved cardiac phase/amplitude functional imaging  

International Nuclear Information System (INIS)

[en] In multiple gated cardiac bloodpool studies using sup(99m)Tc, the motility of the ventricles may be assessed by functional imaging by temporal Fourier analysis. In the present study some theoretical and practical objections to this computation and presentation scheme are overcome. The method provides by a more realistic model, requires only a black and white display (video or plotter) and produces amplitude modulation of the phase image, thus combining the two images into one. Amplitude modulated phase maps allow presentation of information that is essentially dynamic of nature in a hard-copy black and white format. These maps serve as patient documentation which is more easily accessible than digital storage media or videotapes. (UK)

1980-01-01

232

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Dimsdle, Jeffrey William (Overland Park, KS)

2007-07-03

233

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Dimsdle, Jeffrey William (Overland Park, KS)

2007-10-02

234

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Dimsdle, Jeffrey William (Overland Park, KS)

2008-10-21

235

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Dimsdle, Jeffrey William (Overland Park, KS)

2009-09-01

236

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

Dimsdle, Jeffrey William (Overland Park, KS)

2007-07-17

237

Roots of Amplitudes  

CERN Multimedia

In a recent paper [arXiv:1106.0166], boundary contributions in BCFW recursion relations have been related to roots of amplitudes. In this paper, we make several analyses regarding to this problem. Firstly, we use different ways to re-derive boundary BCFW recursion relations given in [arXiv:1106.0166]. Secondly, we generalize factorization limits to z-dependent ones, where information of roots is more transparent. Then, we demon- strate our analysis with several examples. In general, relations from factorization limits cannot guarantee to find explicit expressions for roots.

Feng, Bo; Luo, Hui; Luo, Mingxing

2011-01-01

238

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

239

Improved Estimation of the Amplitude Envelope of Time Domain Signals Using True Envelope Cepstral Smoothing.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The amplitude modulations of musical instrument sounds and speech are important perceptual cues. Accurate estimation of the amplitude, or equivalently energy, envelope of a time-domain signal (waveform) is not a trivial task, though. Ideally, the amplitude envelope should outline the waveform connec...

Freitas Caetano, Marcelo; Rodet, Xavier

240

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; Todorov, Ivan

2013-01-01

 
 
 
 
241

Generator of Stable Amplitude Spectroscopy Pulses  

CERN Multimedia

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

Subbotin, V G; Voinov, A A

2004-01-01

242

Dissolving N=4 loop amplitudes into QCD tree amplitudes  

International Nuclear Information System (INIS)

We use the infrared consistency of one-loop amplitudes in N=4 Yang-Mills theory to derive a compact analytic formula for a tree-level next-to-next-to-maximal helicity-violating gluon scattering amplitude in QCD, the first such formula known. We argue that the infrared conditions, coupled with recent advances in calculating one-loop box coefficients, can give a new tool for computing tree-level amplitudes in general. Our calculation suggests that many amplitudes have a structure which is even simpler than that revealed so far by current twistor-space constructions.

2005-03-18

243

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

Science.gov (United States)

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 ?-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

2010-01-01

244

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

245

Excitation of sustained oscillations with an amplitude belonging to a descrete series of possible stable amplitudes  

International Nuclear Information System (INIS)

Sustained oscillation excitation is considered under the action of an internal nonperiodic force. It is shown that besides the basic modulation energy channel there exists also a parametric one. Therefore the mechanism of phase selftrimming which is the basis of the energy exchange and the source of the sustained oscillations appears to be more flexible. System oscillations show much more independence on the internal factors fluctuations and of the amplitude on the applied force. 4 refs.

1990-01-01

246

Large Amplitude Oscillations in Prominences  

CERN Multimedia

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

247

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

248

Beam quality improvement by joint compensation of amplitude and phase.  

UK PubMed Central (United Kingdom)

The M² factor could be decomposed as amplitude term and phase term. A method to improve the beam quality of laser beams is proposed. In our method, the amplitude and phase of a laser beam are both compensated in order to improve the beam quality completely. In experiment, a laser amplifier is set to modulate the amplitude to Gaussian type, and a deformable mirror is used to compensate the phase aberration. The laser beam is well compensated by our method; the beam quality factor of the laser is improved from 1.7 to 1.1.

Gong ML; Qiu Y; Huang L; Liu Q; Yan P; Zhang HT

2013-04-01

249

?-? interaction amplitudes with chiral constraints  

International Nuclear Information System (INIS)

The ?? interaction amplitudes have been calculated using a three coupled channel model both with and without constraints imposed by chiral models. Roy's equations have been used to compare the amplitudes and to study the role played by chiral constraints in the ?? interaction. (author)

2000-01-01

250

Dirac-eikonal scattering amplitude  

Energy Technology Data Exchange (ETDEWEB)

The fixed energy Dirac equation using scalar plus fourth component vector potentials is solved in the eikonal limit. The Dirac-eikonal amplitude can be written in the familiar integral over impact parameter form. Results of model calculations using the Dirac-eikonal amplitude are compared with those of a partial wave solution for parameters appropriate to intermediate energy proton nucleus scattering.

Amado, R.D.; Piekarewicz, J.; Sparrow, D.A.; McNeil, J.A.

1983-10-01

251

Intrinsic modulational Alfvenic turbulence  

Energy Technology Data Exchange (ETDEWEB)

The nonlinear dynamics of a finite-amplitude Alfven wave in a dispersive modulation regime is analysed. Use is made of a conservative model to show that turbulence may arise via deterministic chaos. The behaviour of the system is studied as one varies the initial amplitude of the pump Alfven wave, the dispersion parameter and the plasma parameter {beta}. (Author).

Oliveira, L.P.L. de; Rizzato, F.B. [Universidad Federal do Rio Grande do Sul, Inst. de Fisica, Porto Alegre, RS (Brazil); Chian, A.C.-L. [Instituto Nacional de Pesquisas Espaciais-INPE, Sao Jose dos Campos, SP (Brazil)

1997-10-01

252

Intrinsic modulational Alfvenic turbulence  

International Nuclear Information System (INIS)

The nonlinear dynamics of a finite-amplitude Alfven wave in a dispersive modulation regime is analysed. Use is made of a conservative model to show that turbulence may arise via deterministic chaos. The behaviour of the system is studied as one varies the initial amplitude of the pump Alfven wave, the dispersion parameter and the plasma parameter ?. (Author).

1997-01-01

253

Intrinsic modulational Alfvenic turbulence  

International Nuclear Information System (INIS)

The nonlinear dynamics of a finite-amplitude Alfven wave in a disperse modulational regime is analyzed. A route to Hamiltonian turbulent dynamics is found and the dependence of the degree in which the dynamics are turbulent on the initial amplitude of the pump Alfven wave and the parameter ? is studied. (author). 16 refs., 1 fig.

1995-01-01

254

Intrinsic modulational Alfvenic turbulence  

Energy Technology Data Exchange (ETDEWEB)

The nonlinear dynamics of a finite-amplitude Alfven wave in a disperse modulational regime is analyzed. A route to Hamiltonian turbulent dynamics is found and the dependence of the degree in which the dynamics are turbulent on the initial amplitude of the pump Alfven wave and the parameter {beta} is studied. (author). 16 refs., 1 fig.

Oliveira, L.P.L.; Rizzato, F.B. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica; Chian, A.C.L. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil)

1995-12-31

255

The pulsed amplitude unit for the SLC  

International Nuclear Information System (INIS)

[en] 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

1987-01-01

256

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 is a part of the system that controls the output of Klystrons 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.

1987-01-01

257

Substorm statistics: Occurrences and amplitudes  

Energy Technology Data Exchange (ETDEWEB)

The occurrences and amplitudes of substorms are statistically investigated with the use of three data sets: the AL index, the Los Alamos 3-satellite geosynchronous energetic-electron measurements, and the GOES-5 and -6 geosynchronous magnetic-field measurements. The investigation utilizes {approximately} 13,800 substorms in AL, {approximately} 1400 substorms in the energetic-electron flux, and {approximately} 100 substorms in the magnetic field. The rate of occurrence of substorms is determined as a function of the time of day, the time of year, the amount of magnetotail bending, the orientation of the geomagnetic dipole, the toward/away configuration of the IMF, and the parameters of the solar wind. The relative roles of dayside reconnection and viscous coupling in the production of substorms are assessed. Three amplitudes are defined for a substorms: the jump in the AL index, the peak of the >30-keV integral electron flux at geosynchronous orbit near midnight, and the angle of rotation of the geosynchronous magnetic field near midnight. The substorm amplitudes are statistically analyzed, the amplitude measurements are cross correlated with each other, and the substorm amplitudes are determined as functions of the solar-wind parameters. Periodically occurring and randomly occurring substorms are analyzed separately. The energetic-particle-flux amplitudes are consistent with unloading and the AL amplitudes are consistent with direct driving plus unloading.

Borovsky, J.E.; Nemzek, R.J.

1994-05-01

258

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

259

Discontinuity Formulas for Multiparticle Amplitudes.  

Science.gov (United States)

It is shown how discontinuity formulas for multiparticle scattering amplitudes are derived from unitarity and analyticity. The assumed analyticity property is the normal analytic structure, which was shown to be equivalent to the space-time macrocausality...

H. P. Stapp

1976-01-01

260

Spin Filter in DVCS amplitudes  

CERN Multimedia

In deeply virtual Compton scattering (DVCS) it is found that in some kinematics angular momentum is not conserved if the amplitudes are calculated in terms of widely used reduced operators. Consequently, those kinematics will lead to the wrong analysis of experimental data in terms of generalized parton distributions. Contrary to common lore, the contribution of the longitudinally polarized virtual photon should not be neglected in the analysis of DVCS amplitudes.

Ji, Bernard L G Bakker Chueng-Ryong

2010-01-01

 
 
 
 
261

One loop multiphoton helicity amplitudes  

CERN Document Server

We use the solutions to the recursion relations for double-off-shell fermion currents to compute helicity amplitudes for $n$-photon scattering and electron-positron annihilation to photons in the massless limit of QED. The form of these solutions is simple enough to allow {\\it all}\\ of the integrations to be performed explicitly. For $n$-photon scattering, we find that unless $n=4$, the amplitudes for the helicity configurations (+++...+) and (-++...+) vanish to one-loop order.

Mahlon, G

1994-01-01

262

Semiclassical approach to fidelity amplitude  

CERN Document Server

The fidelity amplitude is a quantity which is of paramount importance in echo type experiments. We use semiclassical theory to study the average fidelity amplitude for quantum chaotic systems under external perturbation. We explain analytically two extreme cases: the random dynamics limit --attained approximately by strongly chaotic systems-- and the random perturbation limit, which shows a Lyapunov decay. Numerical simulations help us bridge the gap between both extreme cases.

García-Mata, Ignacio; Wisniacki, Diego A

2011-01-01

263

Amplitude death state for hearing  

CERN Document Server

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

Ahn, Kang-Hun

2012-01-01

264

Motivic Amplitudes and Cluster Coordinates  

CERN Document Server

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

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

2013-01-01

265

The modulation of immunity  

Energy Technology Data Exchange (ETDEWEB)

This book contains 13 chapters. Some of the chapter titles are: Modulation of Immunity by Thymus-Derived Lymphocytes; Modulation of Immunity by Macrophages; Modulation of Immunity by Soluble Mediators; Viruses and the Immune Response; and Methanol Extraction Residue: Effects and Mechanisms of Action.

Mitchell, M.S.

1985-01-01

266

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

UK PubMed Central (United Kingdom)

The ability of hemoproteins to discriminate between diatomic molecules, and the subsequent affinity for their chosen ligand, is fundamental to the existence of life. These processes are often controlled by precise structural arrangements in proteins, with heme pocket residues driving reactivity and specificity. One such protein is cytochrome c', which has the ability to bind nitric oxide (NO) and carbon monoxide (CO) on opposite faces of the heme; a property shared with soluble guanylate cycle. Like soluble guanylate cyclase, cytochrome c' also excludes O2 completely from the binding pocket. Previous studies have shown that the NO binding mechanism is regulated by a proximal arginine (R124) and a distal leucine (L16) residue. Here, we have investigated the roles of these residues in maintaining the affinity for NO in the heme binding environment by using various time resolved spectroscopy techniques that span the entire femtosecond-second temporal range in the UV-vis, and femtosecond-nanosecond by IR. Our findings indicate that the tightly regulated NO rebinding events following excitation in wild-type cytochrome c' are affected in the R124A variant. With R124A, vibrational and electronic changes extend continuously across all time scales (from fs-s), in contrast to wild-type cytochrome c', and an L16A variant. Based on these findings, we propose a NO (re-)binding mechanism for the R124A variant of cytochrome c' that is distinct from that in wild-type cytochrome c'. In the wider context, these findings emphasize the importance of heme pocket architecture in maintaining the reactivity of hemoproteins towards their chosen ligand and demonstrate the power of spectroscopic probes spanning a wide temporal range. This article is protected by copyright. All rights reserved.

Russell HJ; Hardman SJ; Heyes DJ; Hough MA; Greetham GM; Towrie M; Hay S; Scrutton NS

2013-09-01

267

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

1993-01-01

268

Propagation amplitude in spinorial gravity  

Energy Technology Data Exchange (ETDEWEB)

We consider the propagator between two field configurations in the quantum theory of gravity based on the new variables of Ashtekar. The central tool in our analysis is the BRST formalism (1986 Phys. Rev. Lett. 57,2244). We use a combination of functional integral and operator techniques to show that the amplitude is expressible as the matrix element of a relatively simple ghost-extended evolution operator. The amplitude is then to be averaged over the kinematic (or gauge) group which is a semi-direct product of the spatial diffeomorphism and local SU(2) groups.

Torre, C.G.

1988-02-01

269

Residual Momentum  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Conventional momentum strategies exhibit substantial time-varying exposures to the Fama and French factors. We show that these exposures can be reduced by ranking stocks on residual stock returns instead of total returns. As a consequence, residual momentum earns risk-adjusted profits that are about...

Blitz, D.C.; Huij, J.J.; Martens, M.P.E.

270

Amino-terminal cysteine residues of RGS16 are required for palmitoylation and modulation of Gi- and Gq-mediated signaling.  

UK PubMed Central (United Kingdom)

RGS proteins (Regulators of G protein Signaling) are a recently discovered family of proteins that accelerate the GTPase activity of heterotrimeric G protein alpha subunits of the i, q, and 12 classes. The proteins share a homologous core domain but have divergent amino-terminal sequences that are the site of palmitoylation for RGS-GAIP and RGS4. We investigated the function of palmitoylation for RGS16, which shares conserved amino-terminal cysteines with RGS4 and RGS5. Mutation of cysteine residues at residues 2 and 12 blocked the incorporation of [3H]palmitate into RGS16 in metabolic labeling studies of transfected cells or into purified RGS proteins in a cell-free palmitoylation assay. The purified RGS16 proteins with the cysteine mutations were still able to act as GTPase-activating protein for Gialpha. Inhibition or a decrease in palmitoylation did not significantly change the amount of protein that was membrane-associated. However, palmitoylation-defective RGS16 mutants demonstrated impaired ability to inhibit both Gi- and Gq-linked signaling pathways when expressed in HEK293T cells. These findings suggest that the amino-terminal region of RGS16 may affect the affinity of these proteins for Galpha subunits in vivo or that palmitoylation localizes the RGS protein in close proximity to Galpha subunits on cellular membranes.

Druey KM; Ugur O; Caron JM; Chen CK; Backlund PS; Jones TL

1999-06-01

271

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

272

Operant Conditioning of Gsr Amplitude.  

Science.gov (United States)

An experimental group of 40 Ss was given a 5 cent-connected light as positive reinforcement contingent on their GSR amplitude following a lever press. A corresponding group of 40 control Ss had their reinforcement schedules yoked to that of their experime...

J. E. Helmer J. J. Furedy

1967-01-01

273

N-loop string amplitude  

International Nuclear Information System (INIS)

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

1986-01-01

274

Veneziano Amplitude for Winding Strings  

CERN Multimedia

String configurations with nonzero winding number describe soliton string states. We compute the Veneziano amplitude for the scattering of arbitrary winding states and show that in the large radius limit the strings always scatter trivially and with no change in the individual winding numbers of the strings. In this limit, then, these states scatter as true solitons.

Khuri, R R

1993-01-01

275

N-loop string amplitude  

Energy Technology Data Exchange (ETDEWEB)

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

Mandelstam, S.

1986-06-01

276

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

277

Amplitude alignment for preshower detector  

CERN Multimedia

The Preshower detector together with the Cherenkov Nitroge n dete ctor are used for electron - positron background rejection using amplitude information . I n the present work, the Preshower signal amplitu - des are corrected for the light attenuation and inhomo g e n eity of individual Preshower scintillator slabs

Pentia, M; Yazkov, V

2012-01-01

278

Variable amplitude fatigue crack growth behavior - a short overview  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2011-03-15

279

Twisted Amplitude Phase Shift Keying  

Science.gov (United States)

Several modulation techniques are defined in digital modulation, Here we are discussing about in four modulation techniques,8-PSK,8-TAPSK,16- TAPSK and 16-QAM. In the paper we derive minimum non coherent distance(dnc)of block coded TAPSK and compare it with different modulation techniques, i.e. 8-PSK and 16-QAM using linear component codes. If the block length N is very small.NBC-16-TAPSK performs best among all non-coherent scheme and NBC-16QAM perform wrose due to its small minimum noncoherent distance. However, if the block length N is not short, NBC-16QAM has the best error performance because the code words with small non-coherent distances are rare.

2013-03-01

280

Finiteness of multi-loop superstring amplitudes  

CERN Multimedia

Superstring amplitudes of an arbitrary genus are calculated through super-Schottky parameters by a summation over the fermion strings. For a calculation of divergent multi-loop fermion string amplitudes a supermodular invariant regularization procedure is used. A cancellation of divergences in the superstring amplitudes is established. Grassmann variables are integrated, the superstring amplitudes are obtained to be explicitly finite and modular invariant.

Danilov, G S

1998-01-01

 
 
 
 
281

Multidimensional signal modulation and/or demodulation for data communications  

Energy Technology Data Exchange (ETDEWEB)

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

282

SCRUNCHER phase and amplitude control  

International Nuclear Information System (INIS)

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

1992-01-01

283

Scruncher phase and amplitude control  

International Nuclear Information System (INIS)

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

1992-01-01

284

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

285

Quasar variability correlations with amplitude  

CERN Document Server

The relation between quasar variability and parameters such as luminosity andredshift has been a matter of hot debate over the last few years with manypapers on the subject. Any correlations which can be established will have aprofound effect on models of quasar structure and evolution. The sample ofquasars in ESO/SERC field 287 contains over 600 quasars in the range 0 < z <3.5 and is now large enough to bin in luminosity and redshift, and givedefinitive measures of the correlations. We find no significant correlationbetween amplitude and redshift, except perhaps at very low redshift, but aninverse correlation between amplitude and luminosity. This is examined in thecontext of various models for quasar variability.

Hawkins, M R S

2000-01-01

286

SCRUNCHER phase and amplitude control  

Energy Technology Data Exchange (ETDEWEB)

The analog controller for phase and amplitude control of a 402.5 MHz super conducting cavity is described in this paper. The cavity is a single cell with niobium explosively bonded to a copper cavity. It is used as an energy compressor for pions at the Clinton P. Anderson Meson Physics Facility (LAMPF). The controller maintains cavity frequency to within 4 degrees in phase of the LAMPF beam frequency. Field amplitude is maintained to within 2 percent. This control is accomplished at critical coupling (Q loaded of 1 {times} 10{sup 9}) with the use of only a 30 watt rf amplifier for accelerating fields of 6 MV/m. The design includes the use of piezoelectric crystals for fast resonance control. Three types of control, self excited VCO, and a reference frequency driven, were tried on this cavity and we present a comparison of their performance.

DeHaven, R.A.; Morris, C.L.; Johnson, R.; Davis, J.; O' Donnell, J.M.

1992-01-01

287

SCRUNCHER phase and amplitude control  

Energy Technology Data Exchange (ETDEWEB)

The analog controller for phase and amplitude control of a 402.5 MHz super conducting cavity is described in this paper. The cavity is a single cell with niobium explosively bonded to a copper cavity. It is used as an energy compressor for pions at the Clinton P. Anderson Meson Physics Facility (LAMPF). The controller maintains cavity frequency to within 4 degrees in phase of the LAMPF beam frequency. Field amplitude is maintained to within 2 percent. This control is accomplished at critical coupling (Q loaded of 1 {times} 10{sup 9}) with the use of only a 30 watt rf amplifier for accelerating fields of 6 MV/m. The design includes the use of piezoelectric crystals for fast resonance control. Three types of control, self excited VCO, and a reference frequency driven, were tried on this cavity and we present a comparison of their performance.

DeHaven, R.A.; Morris, C.L.; Johnson, R.; Davis, J.; O`Donnell, J.M.

1992-09-01

288

Fringe-free holographic measurements of large-amplitude vibrations.  

UK PubMed Central (United Kingdom)

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

Joud F; Verpillat F; Laloë F; Atlan M; Hare J; Gross M

2009-12-01

289

Fringe-free holographic measurements of large-amplitude vibrations.  

Science.gov (United States)

In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; because of the limited resolution of the images, measurements of large amplitudes are not accessible. We demonstrate a technique that suppresses the necessity of fringe counting--frequency sideband imaging--where the order of the sideband is considered a marker of the amplitude. The measurement is completely local: no comparison with another reference point on the object is necessary. It involves a sharp variation of a signal, which makes it robust against perturbations. The method is demonstrated in an experiment made with a vibrating clarinet reed; phase modulations as large as 1000 rad have been measured. PMID:19953166

Joud, F; Verpillat, F; Laloë, F; Atlan, M; Hare, J; Gross, M

2009-12-01

290

Small amplitude vibrations measuring systems  

International Nuclear Information System (INIS)

There is a growing number of instruments and techniques that require the measurement of very small amplitude vibrations. The goal of this paper is to review some of these techniques and to point out, in a formal manner, their main features concerning the signal-to-noise ratio (SNR) and the detection limit (DL). The noise sources and the influence of the system design over the noise level are identified from the specific mathematical equation of the SNR. (author) 10 figs., 23 refs

1995-01-01

291

Nonlinear graphene plasmonics: amplitude equation  

CERN Document Server

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

Gorbach, A V

2013-01-01

292

Discontinuity formulas for multiparticle amplitudes  

International Nuclear Information System (INIS)

The aim of these lectures is to show how discontinuity formulas for muliparticle scattering amplitudes are derived from unitarity and analyticity. The assumed analyticity property is the normal analytic structure, which was shown in the previous lecture series to be equivalent to the space-time macrocausality condition. The discontinuity formulas to be derived are the basis of the multi-particle fixed-t dispersion relations. upon which the subsequent lecture series on Regge theory is based. (Auth.)

1975-06-02

293

Phase Variation of Hadronic Amplitudes  

CERN Document Server

The phase variation with angle of hadronic amplitudes is studied with a view to understanding the underlying physical quantities which 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 which 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.

Dedonder, J P; Nuseirat, Mutazz

2007-01-01

294

Finite Amplitude Electron Plasma Waves in a Cylindrical Waveguide  

DEFF Research Database (Denmark)

The nonlinear behaviour of the electron plasma wave propagating in a cylindrical plasma waveguide immersed in an infinite axial magnetic field is investigated using the Krylov-Bogoliubov-Mitropolsky perturbation method, by means of which is deduced the nonlinear Schrodinger equation governing the long-time slow modulation of the wave amplitude. From this equation the amplitude-dependent frequency and wavenumber shifts are calculated, and it is found that the electron waves with short wavelengths are modulationally unstable with respect to long-wavelength, low-frequency perturbations. It is further shown that an oscillatory solution of the Korteweg-de Vries equation, which is derived in the small wavenumber region, satisfies the small wavenumber limit of the nonlinear Schrodinger equation

Juul Rasmussen, Jens

1978-01-01

295

Amplitude modulation of androgen signaling by c-MYC.  

Science.gov (United States)

Androgen-stimulated growth of the molecular apocrine breast cancer subtype is mediated by an androgen receptor (AR)-regulated transcriptional program. However, the molecular details of this AR-centered regulatory network and the roles of other transcription factors that cooperate with AR in the network remain elusive. Here we report a positive feed-forward loop that enhances breast cancer growth involving AR, AR coregulators, and downstream target genes. In the absence of an androgen signal, TCF7L2 interacts with FOXA1 at AR-binding sites and represses the basal expression of AR target genes, including MYC. Direct AR regulation of MYC cooperates with AR-mediated activation of HER2/HER3 signaling. HER2/HER3 signaling increases the transcriptional activity of MYC through phosphorylation of MAD1, leading to increased levels of MYC/MAX heterodimers. MYC in turn reinforces the transcriptional activation of androgen-responsive genes. These results reveal a novel regulatory network in molecular apocrine breast cancers regulated by androgen and AR in which MYC plays a central role as both a key target and a cooperating transcription factor to drive oncogenic growth. PMID:23530127

Ni, Min; Chen, Yiwen; Fei, Teng; Li, Dan; Lim, Elgene; Liu, X Shirley; Brown, Myles

2013-03-25

296

Amplitude modulation of androgen signaling by c-MYC.  

UK PubMed Central (United Kingdom)

Androgen-stimulated growth of the molecular apocrine breast cancer subtype is mediated by an androgen receptor (AR)-regulated transcriptional program. However, the molecular details of this AR-centered regulatory network and the roles of other transcription factors that cooperate with AR in the network remain elusive. Here we report a positive feed-forward loop that enhances breast cancer growth involving AR, AR coregulators, and downstream target genes. In the absence of an androgen signal, TCF7L2 interacts with FOXA1 at AR-binding sites and represses the basal expression of AR target genes, including MYC. Direct AR regulation of MYC cooperates with AR-mediated activation of HER2/HER3 signaling. HER2/HER3 signaling increases the transcriptional activity of MYC through phosphorylation of MAD1, leading to increased levels of MYC/MAX heterodimers. MYC in turn reinforces the transcriptional activation of androgen-responsive genes. These results reveal a novel regulatory network in molecular apocrine breast cancers regulated by androgen and AR in which MYC plays a central role as both a key target and a cooperating transcription factor to drive oncogenic growth.

Ni M; Chen Y; Fei T; Li D; Lim E; Liu XS; Brown M

2013-04-01

297

Voltage-Controlled PAM (Pulse Amplitude Modulation) Inverter.  

Science.gov (United States)

For the variable-speed drive in industry, the system using a squirrel-cage induction motor is increasing in demand, with the requirements on the control functions increasing in multifariousness. In order to answer such a requirement, a series of VVVF-cont...

Y. Takeda Y. Sanaka N. Katsurayama

1984-01-01

298

Solid residues  

Energy Technology Data Exchange (ETDEWEB)

A summary is presented of the many investigations that have been done on solid residues of atmospheric fluid bed combustion (AFBC). These residues are bed ash, cyclone ash and bag filter ash. Physical and chemical properties are discussed and then the various uses of residues (in fillers, bricks, gravel, and for recovery of aluminium) are summarised. Toxicological properties of fly ash and stack ash are discussed as are risks of pneumoconiosis for workers handling fly ash, and contamination of water by ashes. On the basis of present information it is concluded that risks to public health from exposure to emissions of coal fly ash from AFBC appear small or negligible as are health risk to workers in the coal fly ash processing industry. 35 refs., 5 figs., 12 tabs.

Mulder, E.; Duin, P.J. van; Grootenboer, G.J. [TNO Environmental and Energy Research, Apeldoorn (Netherlands)

1995-05-01

299

Interpolating axial anomaly induced amplitudes  

International Nuclear Information System (INIS)

We propose an interpolating formula for the amplitude induced by the axial anomaly, concentrating on the ?0?*?* transition form factor. Our form factor is constructed by the 'vector meson pole terms' and the 'anomaly terms', in which the anomaly terms can be essentially evaluated by the triangle quark graph. We pay our attention to the anomaly term and make intensive analysis of the existing experimental data, i.e., the electromagnetic ?0 and ? transition form factors. Our result shows that it is essential to use the constituent quark mass instead of the current quark mass in evaluating the anomaly term from the triangle graph. (author).

1994-01-01

300

Forward amplitude in pion deuteron  

International Nuclear Information System (INIS)

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

1979-01-01

 
 
 
 
301

Amplitude measurements of Faraday waves.  

Science.gov (United States)

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of epsilon approximately equal 20%. The validity of an existing perturbation analysis is found to be limited to epsilon<2.5%. PMID:11308766

Wernet, A; Wagner, C; Papathanassiou, D; Müller, H W; Knorr, K

2001-02-27

302

Amplitude measurements of Faraday waves.  

UK PubMed Central (United Kingdom)

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of epsilon approximately equal 20%. The validity of an existing perturbation analysis is found to be limited to epsilon<2.5%.

Wernet A; Wagner C; Papathanassiou D; Müller HW; Knorr K

2001-03-01

303

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+).

2010-01-01

304

Generalized Compton Amplitudes In Quantum Chromodynamics  

CERN Multimedia

In this dissertation we describe results of our studies of generalized Compton amplitudes. We have calculated the one-loop corrections to the amplitude in the coordinate representation in terms of nonlocal string light-ray operators. We have also developed a consistent approach to the problem of constructing the gauge invariant Compton amplitude and obtained an expression for the explicitly gauge invariant amplitude which includes all the generalized target-mass corrections.

Grigentch, I

2000-01-01

305

B-meson distribution amplitudes  

Energy Technology Data Exchange (ETDEWEB)

We have calculated 2-to-2 renormalisation kernels of heavy-light light-ray operators in coordinate space using light-cone gauge. Special attention is turned to meson-vacuum matrix elements of these operators, the B- or D-meson light-cone distribution amplitudes (LCDA). At one loop level light-cone gauge reduces all renormalisation kernels to two-particle kernels. The three particle kernels can be constructed by simply adding the previously calculated two-particle kernels. Calculations are performed in heavy quark effective theory (HQET). Our results can be compared with the light-light case where the renormalisation kernels exhibit conformal symmetry. We discuss which symmetries of the full conformal group survive after applying the heavy quark limit of QCD and the renormalisation procedure.

Knoedlseder, Michael; Offen, Nils [Universitaet Regensburg (Germany)

2011-07-01

306

Distribution of electromagnetic transition amplitudes  

Energy Technology Data Exchange (ETDEWEB)

In this paper the distribution of electromagnetic transition amplitudes is described in terms of fluctuations about a gaussian secular variation (as a function of initial and final energies) according to the Porter-Thomas assumption. Explicit formulas are derived both for the case (i) that ..sigma..subW'vertical strokevertical stroke/sup 2/ is replaced by its local average and (ii) that ..sigma..subW'vertical strokevertical stroke/sup 2/ is treated as a stochastic variable. The resulting distribution function appears to possess a monomial tail. Comparisons with shell-model results are made.

Verbaarschot, J.J.M.; Brussaard, P.J.

1985-04-01

307

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

308

Residual stress  

Energy Technology Data Exchange (ETDEWEB)

This book is intended to give the reader a firm foundation in the theory of residual stress measurement with x-rays, as well as a comprehensive understanding of the experimental concepts involved in carrying out such a measurement. It is the only book available that covers all the new techniques such as separation of macro and micro residual stresses, triaxial stress measurement, as well as the errors associated with such techniques. The book is written for engineers and scientists who utilize non-destructive stress analysis in the field as well as for students in a discipline that involves non-destructive stress analysis. The book covers all topics (elasticity/plasticity, x-rays, measurement techniques, etc.) that impact residual stress analysis with x-rays. Problems at the end of selected chapters can be used to test the knowledge of the reader on the material covered therein, as well as providing a working model of the analysis that can be easily applied to different situations.

Noyan, I.C.; Cohen, J.B.

1986-01-01

309

Dolphin and sea lion auditory evoked potentials in response to single and multiple swept amplitude tones.  

UK PubMed Central (United Kingdom)

Measurement of the auditory steady-state response (ASSR) is increasingly used to assess marine mammal hearing. These tests normally entail measuring the ASSR to a sequence of sinusoidally amplitude modulated tones, so that the ASSR amplitude function can be defined and the auditory threshold estimated. In this study, an alternative method was employed, where the ASSR was elicited by an amplitude modulated stimulus whose sound pressure level was slowly varied, or "swept," over a range of levels believed to bracket the threshold. The ASSR amplitude function was obtained by analyzing the resulting grand average evoked potential using a short-time Fourier transform. The suitability of this technique for hearing assessment of bottlenose dolphins and California sea lions was evaluated by comparing ASSR amplitude functions and thresholds obtained with swept amplitude and discrete, constant amplitude stimuli. When factors such as the number of simultaneous tones, the number of averages, and the frequency analysis window length were taken into account, the performance and time required for the swept-amplitude and discrete stimulus techniques were similar. The decision to use one technique over another depends on the relative importance of obtaining suprathreshold information versus the lowest possible thresholds.

Finneran JJ; Mulsow J; Schlundt CE; Houser DS

2011-08-01

310

Modulational instabilities in discrete lattices  

Energy Technology Data Exchange (ETDEWEB)

We study analytically and numerically modulational instabilities in discrete nonlinear chains, taking the discrete Klein-Gordon model as an example. We show that discreteness can drastically change the conditions for modulational instability; e.g., at small wave numbers a nonlinear carrier wave is unstable to all possible modulations of its amplitude if the wave amplitude exceeds a certain threshold value. Numerical simulations show the validity of the analytical approach for the initial stage of the time evolution, provided that the harmonics generated by the nonlinear terms are considered. The long-term evolution exhibits chaoticlike states.

Kivshar, Y.S. (Institut fuer Theoretische Physik I, Heinrich-Heine Universitaet Duesseldorf, D-4000 Duesseldorf 1 (Germany)); Peyrard, M. (Physique NonLineaire, Ondes et Structures Coherentes, Faculte des Sciences, 6 boulevard Gabriel, F-21000 Dijon (France) Center for Nonlinear Studies, MS B258, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1992-09-15

311

Endpoint symmetries of helicity amplitudes  

CERN Document Server

We investigate helicity amplitudes (HAs) of $A \\to B C$-type decays for arbitrary spin towards the kinematic endpoint. We show that they are proportional to product of Clebsch-Gordan coefficients (CGC) and the velocity to some positive power. The latter can be zero in which case the HA is non-vanishing at the endpoint. In essence the spatial rotational symmetry, broken by the relative spatial momenta of the particles, is restored at the kinematic endpoint. Therefore SO(3) and SU(2), for bosons and fermion in the decay, act like a global internal symmetry groups. Some of our results can be understood in terms of the Wigner- Eckart theorem. The findings are useful for i) checking theoretical computations and ii) the case where there is a sequence of decays, say $B \\to B_1B_2$ with the pair $(B_1B_2)$ not interacting (significantly) with the $C$-particle. An example is $H \\to Z Z^* \\to 4\\ell$ where our findings might be of use for experimentally determining the Higgs quantum numbers. Angular observables, which a...

Zwicky, Roman

2013-01-01

312

Leading singularities of the two-loop six-particle maximally helicity violating amplitude  

International Nuclear Information System (INIS)

We use the leading singularity technique to determine the planar six-particle two-loop maximally helicity violating amplitude in N=4 super Yang-Mills theory in terms of a simple basis of integrals. Our result for the parity-even part of the amplitude agrees with the one recently presented in 1. The parity-odd part of the amplitude is a new result. The leading singularity technique reduces the determination of the amplitude to finding the solution to a system of linear equations. The system of equations is easily found by computing residues. We present the complete system of equations, which determines the whole amplitude, and solve the two-by-two blocks analytically. Larger blocks are solved numerically in order to test the Anastasiou Bern Dixon Kosower/Bern Dixon Smirnov iterative structure.

2008-11-15

313

Compact dynatron modulator  

CERN Multimedia

It is proposed to use a dynatron effect to modulate the voltage across the vacuum inverted coaxial diode with magnetic insulation supplied by an external pulsed high-voltage source connected to the modulator via the RL-circuit. Oscillations of the voltage due to oscillating regime of diode charging and/or azimuthal instability of a rotating electron flow simulates back-bombardment electron flow to the cathode and leads to power spikes of secondary emission current exceeding the primary one. As a result,the amplitude of oscillations grows and the system can turn the modulator and its possible applications.

Agafonov, A V

2001-01-01

314

All-fibre source of amplitude-squeezed light pulses  

CERN Document Server

An all-fibre source of amplitude squeezed solitons utilizing the self-phase modulation in an asymmetric Sagnac interferometer is experimentally demonstrated. The asymmetry of the interferometer is passively controlled by an integrated fibre coupler, allowing for the optimisation of the noise reduction. We have carefully studied the dependence of the amplitude noise on the asymmetry and the power launched into the Sagnac interferometer. Qualitatively, we find good agreement between the experimental results, a semi-classical theory and earlier numerical calculations [Schmitt etl.al., PRL Vol. 81, p.2446, (1998)]. The stability and flexibility of this all-fibre source makes it particularly well suited to applications in quantum information science.

Meissner, M; Heersink, J; Gaber, T; Wietfeld, A; Leuchs, G; Andersen, U L; Meissner, Markus; Marquardt, Christoph; Heersink, Joel; Gaber, Tobias; Wietfeld, Andr\\'e; Leuchs, Gerd; Andersen, Ulrik L.

2004-01-01

315

Recognition of OFDM Modulation Method  

Directory of Open Access Journals (Sweden)

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

K. Ulovec

2008-01-01

316

Activated escape of periodically modulated systems  

CERN Document Server

The rate of noise-induced escape from a metastable state of a periodically modulated overdamped system is found for an arbitrary modulation amplitude $A$. The instantaneous escape rate displays peaks that vary with the modulation from Gaussian to strongly asymmetric. The prefactor $\

Dykman, M I

2005-01-01

317

Gravity and Yang-Mills Amplitude Relations  

CERN Document Server

Using only general features of the S-matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.

Bjerrum-Bohr, N E J; Feng, Bo; Sondergaard, Thomas

2010-01-01

318

Local amplitude equation from non-local dynamics  

CERN Multimedia

We derive a closed equation for the shape of the free surface of a magnetic fluid subject to an external magnetic field. The equation is strongly non-local due to the long range character of the magnetic interaction. We develop a systematic multiple scale perturbation expansion in which the non-locality is reduced to the occurrence of the Hilbert transform of the surface profile. The resulting third order amplitude equation describing the slow modulation of the basic pattern is shown to be purely local.

Friedrichs, R; Friedrichs, Rene; Engel, Andreas

2003-01-01

319

Quantum mechanical amplitude for string propagation  

Energy Technology Data Exchange (ETDEWEB)

The quantum mechanical transition amplitude is calculated between an initial and a final string by using the canonical method based entirely on operators. The final expression for this amplitude is given in terms of the Jacobi theta/sub 4/-function and admits a suggestive geometrical interpretation.

Jimenez Lorenzo, F.; Ramirez Mittelbrunn, J.; Ramon Medrano, M.; Sierra, G.

1986-05-01

320

Quantum mechanical amplitude for string propagation  

International Nuclear Information System (INIS)

The quantum mechanical transition amplitude is calculated between an initial and a final string by using the canonical method based entirely on operators. The final expression for this amplitude is given in terms of the Jacobi theta4-function and admits a suggestive geometrical interpretation. (orig.)

1986-05-01

 
 
 
 
321

BCFW construction of the Veneziano amplitude  

International Nuclear Information System (INIS)

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

2011-06-10

322

Scaling laws for the elastic scattering amplitude  

CERN Multimedia

The partial differential equation for the imaginary part of the elastic scattering amplitude is derived. It is solved in the black disk limit. The asymptotical scaling behavior of the amplitude coinciding with the geometrical scaling is proved. Its extension to preasymptotical region and modifications of scaling laws for the differential cross section are considered.

Dremin, I M

2012-01-01

323

Amplitude Variations in Pulsating Red Supergiants  

CERN Multimedia

We have used long-term AAVSO visual observations and Fourier and wavelet analysis to identify periods and study long-term amplitude variations in 44 red supergiants. Of these, 12 stars had data which were too sparse and/or had low amplitude and/or were without conspicuous peaks in the Fourier spectrum; 6 stars had only long (2500-4000 days) periods without significant amplitude variation. The other 26 stars had one or two periods, either "short" (hundreds of days) or "long" (thousands of days), whose amplitudes varied by up to a factor of 8, but more typically 2-4. The median timescale of the amplitude variation was 18 periods. We interpret the shorter periods as due to pulsation, and the longer periods as analogous to the "long secondary periods" found in pulsating red giants.

Percy, John R

2013-01-01

324

The scattering amplitude for four off-shell tachyons from functional integrals  

International Nuclear Information System (INIS)

[en] We use functional integral techniques to calculate the scattering amplitude for four open off-shell tachyons in Witten's string field theory and show that the residues of the first three poles agree with those obtained using oscillator methods. (orig.)

1988-05-30

325

New approach to electrode kinetic measurements in square-wave voltammetry: amplitude-based quasireversible maximum.  

UK PubMed Central (United Kingdom)

The influence of the potential pulse height of square-wave voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on several frequency-related kinetic parameters. The electrode kinetic measurements are based on a novel feature termed the "amplitude-based quasireversible maximum", manifested as a parabolic dependence of the amplitude-normalized net SW peak current versus the SW amplitude. The position of the amplitude-based quasireversible maximum depends on the standard rate constant of the electrode reaction, enabling estimation of this important kinetic parameter in a simple and fast procedure. The novel quasireversible maximum is attributed to all studied electrode mechanisms, implying that it is a general feature of most electrode mechanisms under conditions of SWV.

Mirceski V; Laborda E; Guziejewski D; Compton RG

2013-06-01

326

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.

1981-07-08

327

Amplitude death with mean-field diffusion.  

UK PubMed Central (United Kingdom)

We study the dynamics of nonlinear oscillators under mean-field diffusive coupling. We observe that this form of coupling leads to amplitude death via a synchronization transition in the parameter space of the coupling strength and mean-field control parameter. A general criterion for amplitude death for any given dynamical system with mean-field diffusion is obtained, and these dynamical transitions are characterized using various indices such as average phase difference, Lyapunov exponents, and average amplitude. This behavior is analyzed in the parameter plane by numerical studies of specific cases of the Landau-Stuart limit-cycle oscillator, and Rössler, Lorenz, FitzHugh-Nagumo excitable, and Chua systems.

Sharma A; Shrimali MD

2012-05-01

328

Multigluon helicity amplitudes involving a quark loop  

CERN Document Server

We apply the solution to the recursion relation for the double-off-shell quark current to the problem of computing one loop amplitudes with an arbitrary number of gluons. We are able to compute amplitudes for photon-gluon scattering, electron-positron annihilation to gluons, and gluon-gluon scattering via a quark loop in the case of like-helicity gluons. In addition, we present the result for the one-loop gluon-gluon scattering amplitude when one of the gluons has opposite helicity from the others.

Mahlon, G

1994-01-01

329

First-order eikonal exchange amplitudes  

Energy Technology Data Exchange (ETDEWEB)

A detailed derivation of a first-order analytic approximation to the electron-hydrogen charge-exchange amplitude in both the Glauber approximation and eikonal approximmations in both post and prior forms is presented. The results are applicable to arbitrary initial states. The approximation is applied to elastic scattering by hydrogen in its ground state, and numerical results for both the modulus and phase of the exchange amplitude are obtained. the analytic approximation converges rapidly to the exact eikonal result with increasing energy. The techniques used in approximating the contribution to the exchange amplitude arising from the electron-nucleus part of the interaction potential are discussed in detail.

Franco, V.; Halpern, A.M.

1982-11-01

330

Eikonal methods applied to gravitational scattering amplitudes  

Science.gov (United States)

We apply factorization and eikonal methods from gauge theories to scattering amplitudes in gravity. We hypothesize that these amplitudes factor into an IR-divergent soft function and an IR-finite hard function, with the former given by the expectation value of a product of gravitational Wilson line operators. Using this approach, we show that the IR-divergent part of the n-graviton scattering amplitude is given by the exponential of the one-loop IR divergence, as originally discovered by Weinberg, with no additional subleading IR-divergent contributions in dimensional regularization.

Naculich, Stephen G.; Schnitzer, Howard J.

2011-05-01

331

A Link Representation for Gravity Amplitudes  

CERN Multimedia

We derive a link representation for all tree amplitudes in N=8 supergravity, from a recent conjecture by Cachazo and Skinner. The new formula explicitly writes amplitudes as contour integrals over constrained link variables, with an integrand naturally expressed in terms of determinants, or equivalently tree diagrams. Important symmetries of the amplitude, such as supersymmetry, parity and (partial) permutation invariance, are kept manifest in the formulation. We also comment on rewriting the formula in a GL(k)-invariant manner, which may serve as a starting point for the generalization to possible Grassmannian contour integrals.

He, Song

2012-01-01

332

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.

Setyamartana Parman; Bambang Ari-Wahjoedi; Edward Halawa; Affiani Machmudah

2012-01-01

333

Magnetization of compositionally modulated CuNi films  

Energy Technology Data Exchange (ETDEWEB)

We report static magnetization measurements on the compositionally modulated ferromagnetic alloy Cu/Ni, which, contrary to earlier ferromagnetic resonance measurements, show the moment per Ni atom is reduced relative to pure Ni. The low-temperature magnetization is found to vary linearly with modulation amplitude, but, surprisingly, the Curie temperature is found to be almost amplitude independent.

Zheng, J.Q.; Falco, C.M.; Ketterson, J.B.; Schuller, I.K.

1981-03-15

334

Magnetization of compositionally modulated CuNi films  

International Nuclear Information System (INIS)

[en] We report static magnetization measurements on the compositionally modulated ferromagnetic alloy Cu/Ni, which, contrary to earlier ferromagnetic resonance measurements, show the moment per Ni atom is reduced relative to pure Ni. The low-temperature magnetization is found to vary linearly with modulation amplitude, but, surprisingly, the Curie temperature is found to be almost amplitude independent

1981-03-15

335

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

CERN Multimedia

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

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; Michael J. Cree; Adrian A. Dorrington

2011-01-01

337

Wavebreaking amplitudes in warm, inhomogeneous plasmas  

International Nuclear Information System (INIS)

The effect of plasma temperature on reducing the wavebreaking amplitude of resonantly driven fields in a spatially inhomogeneous plasma is shown. A simple theory is developed, and some applications to laser plasma interactions are given

1979-01-01

338

An analysis of heavy ion scattering amplitudes  

International Nuclear Information System (INIS)

A heurisht method is derived for the analysis of light heavy ion systems. It consists in splitting an oscillatory amplitude into subamplitudes each of them being smooth, at least in modulus. Applications are given

1979-01-01

339

Small amplitude quasi-breathers and oscillons  

CERN Multimedia

Quasi-breathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in Phys. Rev. D. 74, 124003 (2006). QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in $D$ spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, $D_{crit}=4$, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.

Fodor, Gyula; Horváth, Zalán; Lukács, Árpád

2008-01-01

340

Scattering amplitudes for high-energy factorization  

CERN Document Server

A prescription is presented to construct manifestly gauge invariant tree-level scattering amplitudes with one or two off-shell initial-state gluons for processes with arbitrary particles in the final state, which allows for calculations that are efficient and easy to automate. These scattering amplitudes are relevant for factorization schemes beyond collinear factorization that allow the gluons entering the partonic cross section to have non-vanishing transversal momentum components.

van Hameren, A

2013-01-01

 
 
 
 
341

The Cepheid bump progression and amplitude equations  

Energy Technology Data Exchange (ETDEWEB)

It is shown that the characteristic and systematic behavior of the low-order Fourier amplitudes and phases of hydrodynamically generated radial velocity and light curves of Cepheid model sequences is very well captured not only qualitatively but also quantitatively by the amplitude equation formalism. The 2:1 resonance between the fundamental and the second overtone plays an essential role in the behavior of the models 8 refs.

Kovacs, G.; Buchler, J.R. (Florida Univ., Gainesville (USA))

1989-11-01

342

Reduction of the eikonal exchange amplitude  

Energy Technology Data Exchange (ETDEWEB)

It is pointed out that the magnitude of the nuclear-scattering term in the eikonal exchange amplitude is smaller than but not negligible to that of the electronic-scattering term at intermediate energies. It is, therefore, concluded that any approximation scheme which bypasses completely the exchange amplitude at intermediate energies especially at larger scattering angles. Comparison is made between these terms (electronic and nuclear scattering) using their exact eikonal forms as well as their various approximate expressions.

Gien, T.T.

1982-07-01

343

Duality between Wilson Loops and Scattering Amplitudes  

CERN Document Server

We summarise the status of an intriguing new duality between planar maximally helicity violating scattering amplitudes and light-like Wilson loops in N=4 super Yang-Mills. In particular, we focus on the role played by (dual) conformal symmetry, which is made predictive by deriving anomalous conformal Ward identities for the Wilson loops. Assuming the duality, the conformal symmetry of the dual Wilson loops becomes an unexpected new symmetry of scattering amplitudes in N=4 SYM.

Henn, Johannes

2008-01-01

344

Vowel identification by amplitude and phase contrast.  

UK PubMed Central (United Kingdom)

Vowel identification is largely dependent on listeners' access to the frequency of two or three peaks in the amplitude spectrum. Earlier work has demonstrated that, whereas normal-hearing listeners can identify harmonic complexes with vowel-like spectral shapes even with very little amplitude contrast between "formant" components and remaining harmonic components, listeners with hearing loss require greater amplitude differences. This is likely the result of the poor frequency resolution that often accompanies hearing loss. Here, we describe an additional acoustic dimension for emphasizing formant versus non-formant harmonics that may supplement amplitude contrast information. The purpose of this study was to determine whether listeners were able to identify "vowel-like" sounds using temporal (component phase) contrast, which may be less affected by cochlear loss than spectral cues, and whether overall identification improves when congruent temporal and spectral information are provided together. Five normal-hearing and five hearing-impaired listeners identified three vowels over many presentations. Harmonics representing formant peaks were varied in amplitude, phase, or a combination of both. In addition to requiring less amplitude contrast, normal-hearing listeners could accurately identify the sounds with less phase contrast than required by people with hearing loss. However, both normal-hearing and hearing-impaired groups demonstrated the ability to identify vowel-like sounds based solely on component phase shifts, with no amplitude contrast information, and they also showed improved performance when congruent phase and amplitude cues were combined. For nearly all listeners, the combination of spectral and temporal information improved identification in comparison to either dimension alone.

Molis MR; Diedesch A; Gallun F; Leek MR

2013-02-01

345

Vowel identification by amplitude and phase contrast.  

Science.gov (United States)

Vowel identification is largely dependent on listeners' access to the frequency of two or three peaks in the amplitude spectrum. Earlier work has demonstrated that, whereas normal-hearing listeners can identify harmonic complexes with vowel-like spectral shapes even with very little amplitude contrast between "formant" components and remaining harmonic components, listeners with hearing loss require greater amplitude differences. This is likely the result of the poor frequency resolution that often accompanies hearing loss. Here, we describe an additional acoustic dimension for emphasizing formant versus non-formant harmonics that may supplement amplitude contrast information. The purpose of this study was to determine whether listeners were able to identify "vowel-like" sounds using temporal (component phase) contrast, which may be less affected by cochlear loss than spectral cues, and whether overall identification improves when congruent temporal and spectral information are provided together. Five normal-hearing and five hearing-impaired listeners identified three vowels over many presentations. Harmonics representing formant peaks were varied in amplitude, phase, or a combination of both. In addition to requiring less amplitude contrast, normal-hearing listeners could accurately identify the sounds with less phase contrast than required by people with hearing loss. However, both normal-hearing and hearing-impaired groups demonstrated the ability to identify vowel-like sounds based solely on component phase shifts, with no amplitude contrast information, and they also showed improved performance when congruent phase and amplitude cues were combined. For nearly all listeners, the combination of spectral and temporal information improved identification in comparison to either dimension alone. PMID:23007720

Molis, Michelle R; Diedesch, Anna; Gallun, Frederick; Leek, Marjorie R

2012-09-25

346

Amplitudes for Multiple M5 Branes  

CERN Multimedia

We study N=(n,0) super-Poincare invariant six-dimensional massless and five-dimensional massive on-shell amplitudes. We demonstrate that in six dimensions all possible three-point amplitudes involving tensor multiplets are uniquely determined by super-Poincare invariance and are necessarily embedded in gravitational theories. For non-gravitational amplitudes we consider instead five-dimensional massive amplitudes with N=(2,0) supersymmetry, corresponding to compactifying the theory on a circle. Super-Poincare invariance and constraints motivated by four-dimensional S-duality uniquely fix the amplitude as well as the participating multiplets. The on-shell degrees of freedom are shown to match those of the massive particle states that arise from self-dual strings wrapping a circle. Along the way we find interesting hints of a fermionic symmetry in the (2,0) theory, which accompanies the self-dual tensor gauge symmetry. We also discuss novel theories with (3,0) and (4,0) supersymmetry. The three-point amplitudes...

Czech, Bartlomiej; Rozali, Moshe

2011-01-01

347

Twistor-strings and gravity tree amplitudes  

International Nuclear Information System (INIS)

Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem. (paper)

2013-04-07

348

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; Yuekun Wang; Shuai Sun

2012-01-01

349

Reduce residual pulsation in reciprocating compressors  

Energy Technology Data Exchange (ETDEWEB)

Pressure fluctuations occur in the gas in reciprocating compressor connecting lines because of their discontinuous operation. To smooth these fluctuations, pulsation dampeners are provided for each cylinder. The volume, V, of these bottles, which are generally empty, is notably derived from the maximum allowable amplitude, p, of the pressure fluctuation (residual pulsation). Furthermore, V also depends on the cylinder data, the gas and the operating mode. Under otherwise similar conditions, residual pulsation and/or bottle volume can be reduced by additional pressure losses or acoustic filters. The paper describes acoustic resonance, effects of acoustic filters, acoustic filter design, and illustrates with an example.

Ehrich, R. [Babcock-Borsig AG, Berlin (Germany)

1995-07-01

350

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

351

Modulations in the light of the firefly.  

Science.gov (United States)

Continuous light could be produced from the firefly by making it inhale vapours of ethyl acetate. Here we perform such a control experiment on the Indian species of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae), and analyse the light in the microsecond time scale. The amplitude of the continuous train of triangular pulses is apparently altered in accordance with the instantaneous values of a hypothetical signal, which exhibits pulse amplitude modulation (PAM). In addition to sampling in amplitude, this scheme apparently provides sampling in time, representing pulse width modulation (PWM). A Fourier transform spectrum of this waveform shows the 'carrier' frequency and the accompanying 'side bands'. PMID:23385807

Barua, Anurup Gohain

2013-03-01

352

Modulations in the light of the firefly.  

UK PubMed Central (United Kingdom)

Continuous light could be produced from the firefly by making it inhale vapours of ethyl acetate. Here we perform such a control experiment on the Indian species of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae), and analyse the light in the microsecond time scale. The amplitude of the continuous train of triangular pulses is apparently altered in accordance with the instantaneous values of a hypothetical signal, which exhibits pulse amplitude modulation (PAM). In addition to sampling in amplitude, this scheme apparently provides sampling in time, representing pulse width modulation (PWM). A Fourier transform spectrum of this waveform shows the 'carrier' frequency and the accompanying 'side bands'.

Barua AG

2013-03-01

353

High Amplitude Events in relation to Interplanetary disturbances  

Science.gov (United States)

The Sun emits the variable solar wind which interacts with the very local interstellar medium to form the heliosphere. Hence variations in solar activity strongly influence interplanetary space, from the Sun's surface out to the edge of the heliosphere. Superimposed on the solar wind are mass ejections from the Sun and/or its corona which, disturb the interplanetary medium - hence the name "interplanetary disturbances". Interplanetary disturbances are the sources of large-scale particle acceleration, of disturbances in the Earth's magnetosphere, of modulations of galactic cosmic rays in short, they are the prime focus for space weather studies. The investigation deals with the study of cosmic ray intensity, solar wind plasma and interplanetary magnetic field parameters variation due to interplanetary disturbances (magnetic clouds) during an unusual class of days i.e. high amplitude anisotropic wave train events. The high amplitude anisotropic wave train events in cosmic ray intensity has been identified using the data of ground based Goose Bay neutron monitor and studied during the period 1981-94. Even though, the occurrence of high amplitude anisotropic wave trains does not depend on the onset of interplanetary magnetic clouds. But the possibility of occurrence of these events cannot be overlooked during the periods of interplanetary magnetic cloud events. It is observed that solar wind velocity remains higher (> 300) than normal and interplanetary magnetic field B remains lower than normal on the onset of interplanetary magnetic cloud during the passage of these events. It is also noted from the superposed epoch analysis of cosmic ray intensity and geomagnetic activity for high amplitude anisotropic wave train events during the onset of interplanetary magnetic clouds that the increase in cosmic ray intensity and decrease in geomagnetic activity start not at the onset of magnetic clouds but after few days. The north south component of IMF (Bz), IMF (B), proton density (N), proton temperature (T) and latitude angle reaches to their maximum, whereas solar wind velocity (V) and longitude angle reaches to their minimum on the day of magnetic cloud event during the passage of high amplitude anisotropic wave trains. The cosmic ray intensity and Dst index both are found to decrease with the increase of solar wind velocity and reaches to their minimum on the days of high-speed solar wind streams during HAEs.

Mishra, Rajesh Kumar; Agarwal Mishra, Rekha

2012-07-01

354

Scattering amplitudes in open superstring theory  

International Nuclear Information System (INIS)

[en] 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.

2011-01-01

355

Scattering amplitudes in open superstring theory  

Energy Technology Data Exchange (ETDEWEB)

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.

Schlotterer, Oliver

2011-07-15

356

Prominence seismology using small amplitude oscillations  

CERN Multimedia

Quiescent prominences are thin slabs of cold, dense plasma embedded in the much hotter and rarer solar corona. Although their global shape is rather irregular, they are often characterised by an internal structure consisting of a large number of thin, parallel threads piled together. Prominences often display periodic disturbances mostly observed in the Doppler displacement of spectral lines and with an amplitude typically of the order of or smaller than 2--3 km s$^{-1}$, a value which seems to be much smaller than the characteristic speeds of the prominence plasma (namely the Alfv\\'en and sound velocities). Two particular features of these small amplitude prominence oscillations is that they seem to damp in a few periods and that they seem not to affect the whole prominence structure. In addition, in high spatial resolution observations, in which threads can be discerned, small amplitude oscillations appear to be clearly associated to these fine structure constituents. Prominence seismology tries to bring to...

Oliver, R

2009-01-01

357

Amplitude spectra of line-motion stimuli.  

UK PubMed Central (United Kingdom)

The line-motion illusion has been regarded as the result of attention. An alternative interpretation is that the illusion is related to apparent motion which would predict the stimuli to contain motion energy associated with the direction of the illusory motion. In order to examine this possibility Fourier transforms of x-t plots of line-motion stimuli were generated under a variety of conditions. The sums of amplitudes associated with movement in the directions away from the cue relative to that towards the cue were compared to previously published psychophysical observations. It was found that the amplitude sums are largely consistent with the psychophysical results. In the few cases where there were discrepancies between results based on amplitude spectra and psychophysical findings, these discrepancies could be accounted for by making relatively simple and plausible assumptions. The present observations suggest that motion energy may be sufficient to account for the line-motion illusion.

Skottun BC

2011-01-01

358

Pulse-train modulation in a picosecond self-mode-locked laser  

International Nuclear Information System (INIS)

Pulse-train modulation was observed in a picosecond self-mode-locked Ti:sapphire laser with pump-power dependence when it was operated around the degenerate cavity configuration. By increasing the optical pumping power, the envelope of the periodic amplitude modulation splits into two or three clusters with enhanced modulation depth, and the amplitude modulation eventually becomes disordered at higher pump power. The amplitude modulation may be supported by exciting two sets of non-degenerate longitudinally mode-locked supermodes due to spatially inhomogeneous gain modulation in the Ti:sapphire crystal.

2009-07-28

359

Compressible Modules  

CERN Document Server

The main purpose of this paper is to study under what condition compressible modules are critically compressible. A sufficient condition for the injective hull of a critically compressible module to be critically compressible is also provided. Furthermore we prove sufficient conditions for a critically compressible module to be continuous. In addition, some characterization of critically compressible modules in terms of CS modules, nonsingular modules and cyclic modules are also provided

Singh, Abhay K

2012-01-01

360

Duality and effective amplitudes in quantum chromodynamics  

International Nuclear Information System (INIS)

[en] 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[fr] Ce travail est une tentative pour relier les regimes partonique et hadronique de l'interaction forte a l'aide d'un modele d'amplitudes effectives de cordes, qui rend compte des effets de coherence de couleur sans qu'il soit necessaire de restreindre l'espace de phase. La cle de cette approche est la construction, a partir des supercordes ouvertes, d'amplitudes de cordes dont la limite de pente nulle redonne les amplitudes de QCD. Les parametres effectifs (couplage et pente) du modele sont contraints par QCD perturbatif et par l'unitarite des theories de cordes. Quant la pente effective atteint la valeur de la pente de Regge hadronique, ce modele peut se prolonger de maniere raisonnable dans le secteur hadronique. Cette approche donne certaines indications sur la theorie effective des cordes de QCD, et peut egalement permettre une meilleure comprehension de la dualite parton-hadron

1991-01-01

 
 
 
 
361

Massive QCD Amplitudes at Higher Orders  

International Nuclear Information System (INIS)

We consider the factorisation 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 factorisation 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 hadroproduction of heavy quarks. (author)

2007-01-01

362

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.)

2007-11-07

363

Finding the Amplitudes of Migration Hyperbolas  

UK PubMed Central (United Kingdom)

In migration and DMO, the kinematic problem is easier to solve than the amplitudeproblem. Where a purely analytical approach is normally used to obtain theamplitude of a migration operator, we attempt to obtain amplitude informationby combining an assumption of a flat spectrum with the kinematical formulation.This hyperbola whitening is done with a 2-D prediction-error filter. This techniqueis applied to three hyperbolas: a kinematic-only hyperbola, a amplitudecorrectedhyperbola, and an amplitude-corrected hyperbola with a half-derivativefilter. The results show that the assumption of a flat spectrum conflicts with theexistence of an evanescent zone, creating unresolved difficulties.

Ray Abma; Jon Claerbout

364

Leading order electroweak corrections to ? - ?- mixing amplitude  

International Nuclear Information System (INIS)

We perform a two-loop calculation to determine the leading order electroweak corrections to the ? - -? mixing amplitude. In this way, we find out the leading order dependence of this amplitude on the mass of the Higgs boson, MH. This dependence is essentially ln2(MH). The interplay between the top quark and the Higgs boson gives rise to the term mt4ln2(MH) in the effective Lagrangian. These corrections may lead to a few percent correction to the mixing parameter. (author)

1991-01-01

365

Amplitude Selective Damping [ASD]; Amplitudenselektive Daempfung [ASD  

Energy Technology Data Exchange (ETDEWEB)

Theory, simulation results and vehicle tests have shown that amplitude selective damping is a technical solution, which gives a comfortable safety. It cannot compete with the functional range of a semiactive or active system, because the damper is unable to distinguish between single-wheel, pitch and roll movement. As well the active safety cannot be increased using optimized damping by sensing the car environment. But ASD realizes a noticeable ride benefits with relative low on cost, which is important for the price-sensitive segment of subcompact- and mid-size cars. Hence amplitude selective damping is a promising evolutionary step for passive dampers. (orig.)

Gilsdorf, H.J.; Heyn, S.; Gundermann, F. [ZF Sachs AG, Schweinfurt (Germany)

2004-07-01

366

A new look at dynamo cycle amplitudes  

CERN Multimedia

We explore the dependence of the amplitude of stellar dynamo cycle variability (as seen in the Mount Wilson Ca II HK timeseries data) on other stellar parameters. We find that the fractional cycle amplitude A_cyc (i.e. the ratio of the peak-to-peak variation to the average) decreases somewhat with mean activity, increases with decreasing effective temperature, but is not correlated with inverse Rossby number Ro^{-1}. We find that A_cyc increases with the ratio of cycle and rotational frequencies omega_cyc/Omega along two, nearly parallel branches.

Saar, S H; Saar, Steven H.; Brandenburg, Axel

2002-01-01

367

Dual amplitude pulse generator for radiation detectors  

Energy Technology Data Exchange (ETDEWEB)

A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

Hoggan, Jerry M. (Idaho Falls, ID); Kynaston, Ronnie L. (Blackfoot, ID); Johnson, Larry O. (Island Park, ID)

2001-01-01

368

Thresholds for linear amplitude change of a continuous pure tone.  

Science.gov (United States)

The human auditory sensitivity in detecting linear amplitude change of a continuous pure tone has been studied in normal-hearing subjects. It is shown that for short glide durations (less than 100 ms) the duration of the following plateau exerts a significant influence on the DLI. The average DLI at 1 kHz and 60 dB HL was found to be of the order of 0.8 dB when the intensity glide had a duration of 10 ms and was followed by a much longer plateau. For longer glide durations (greater than or equal to 200 ms) the DLI increased significantly as compared with shorter durations. There was no significant difference between increasing and decreasing intensity change. Significantly larger DLIs were found at 250 and 500 Hz than at 1, 2 and 4 kHz. The sound level was found to have a significant influence on the DLI. At low levels of 40 dB HL, and lower, the increase in DLI for detecting sound levels is highly significant. A falling exponential function offers a mathematical description of the relationship with good fit. It is concluded that an integrating mechanism with an integration time of approx. 200 ms could explain the auditory ability to detect linear amplitude glides of a continuous tone. The results are discussed in relation to previous intensity discrimination data, where pulse pairs, continuous intensity modulation or intensity glides were used as stimuli. PMID:756086

Jerlvall, L B; Arlinger, S D; Holmgren, E C

1978-01-01

369

Thresholds for linear amplitude change of a continuous pure tone.  

UK PubMed Central (United Kingdom)

The human auditory sensitivity in detecting linear amplitude change of a continuous pure tone has been studied in normal-hearing subjects. It is shown that for short glide durations (less than 100 ms) the duration of the following plateau exerts a significant influence on the DLI. The average DLI at 1 kHz and 60 dB HL was found to be of the order of 0.8 dB when the intensity glide had a duration of 10 ms and was followed by a much longer plateau. For longer glide durations (greater than or equal to 200 ms) the DLI increased significantly as compared with shorter durations. There was no significant difference between increasing and decreasing intensity change. Significantly larger DLIs were found at 250 and 500 Hz than at 1, 2 and 4 kHz. The sound level was found to have a significant influence on the DLI. At low levels of 40 dB HL, and lower, the increase in DLI for detecting sound levels is highly significant. A falling exponential function offers a mathematical description of the relationship with good fit. It is concluded that an integrating mechanism with an integration time of approx. 200 ms could explain the auditory ability to detect linear amplitude glides of a continuous tone. The results are discussed in relation to previous intensity discrimination data, where pulse pairs, continuous intensity modulation or intensity glides were used as stimuli.

Jerlvall LB; Arlinger SD; Holmgren EC

1978-01-01

370

Calculating real Delbrueck amplitudes on parallel processors  

Energy Technology Data Exchange (ETDEWEB)

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.).

Kahane, S. (Physics Dept., Nuclear Research Center-Negev, Beer Sheva (Israel))

1991-12-01

371

Periods, amplitudes, and luminosities of red supergiants  

Energy Technology Data Exchange (ETDEWEB)

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.

Abramian, G.V.

1984-09-01

372

Duality between Wilson loops and gluon amplitudes  

International Nuclear Information System (INIS)

An intriguing new duality between planar MHV gluon amplitudes and light-like Wilson loops in N=4 super Yang-Mills is investigated. We extend previous checks of the duality by performing a two-loop calculation of the rectangular and pentagonal Wilson loop. Furthermore, we derive an all-order broken conformal Ward identity for the Wilson loops and analyse its consequences. Starting from six points, the Ward identity allows for an arbitrary function of conformal invariants to appear in the expression for the Wilson loop. We compute this function at six points and two loops and discuss its implications for the corresponding gluon amplitude. It is found that the duality disagrees with a conjecture for the gluon amplitudes by Bern et al. A recent calculation by Bern et al. indeed shows that the latter conjecture breaks down at six gluons and at two loops. By doing a numerical comparison with their results we find that the duality between gluon amplitudes and Wilson loops is preserved. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

2009-01-01

373

Cardiac phase: Amplitude analysis using macro programming  

Energy Technology Data Exchange (ETDEWEB)

The analysis of EKG gated radionuclide cardiac imaging data with Fourier amplitude and phase images is becoming a valuable clinical technique, demonstrating location, size, and severity of regional ventricular abnormalities. Not all commercially available nuclear medicine computer systems offer software for phase and amplitude analysis; however, many systems do have the capability of linear image arithmetic using simple macro commands which can easily be sequenced into stored macro-strings or programs. Using simple but accurate series approximations for the Fourier operations, macro programs have been written for a Digital Equipment Corporation Gamma-11 system to obtain phase and amplitude images from routine gated cardiac studies. In addition, dynamic cine-mode presentation of the onset of mechanical systole is generated from the phase data, using only a second set of macro programs. This approach is easily adapted to different data acquisition protocols, and can be used on any system with macro commands for image arithmetic. Key words: Fourier analysis, cardiac cycle, gated blood pool imaging, amplitude image, phase image

Logan, K.W.; Hickey, K.A.

1981-11-01

374

On Calculation of Amplitudes in Quantum Electrodynamics  

CERN Multimedia

A new method of calculation of amplitudes of different processes in quantum electrodynamics is proposed. The method does not use the Feynman technique of trace of product of matrices calculation. The method strongly simplifies calculation of cross sections for different processes. The effectiveness of the method is shown on the cross-section calculation of Coulomb scattering, Compton scattering and electron-positron annihilation.

Karplyuk, Kostyantyn

2012-01-01

375

Elastic amplitudes and power corrections in QCD  

International Nuclear Information System (INIS)

[en] We discuss two power-suppressed quantities in hadronic scattering: elastic amplitudes at fixed angles, and power corrections to inclusive hadronic cross sections. Generalized factorization theorems allow us to determine the asymptotic behavior of elastic scattering, and to relate 1/Q2 corrections in deeply inelastic scattering and the Drell-Yan process. 13 refs

1990-01-01

376

Duality between Wilson loops and gluon amplitudes  

CERN Document Server

An intriguing new duality between planar MHV gluon amplitudes and light-like Wilson loops in N=4 super Yang-Mills is investigated. We extend previous checks of the duality by performing a two-loop calculation of the rectangular and pentagonal Wilson loop. Furthermore, we derive an all-order broken conformal Ward identity for the Wilson loops and analyse its consequences. Starting from six points, the Ward identity allows for an arbitrary function of conformal invariants to appear in the expression for the Wilson loop. We compute this function at six points and two loops and discuss its implications for the corresponding gluon amplitude. It is found that the duality disagrees with a conjecture for the gluon amplitudes by Bern et al. A recent calculation by Bern et al indeed shows that the latter conjecture breaks down at six gluons and at two loops. By doing a numerical comparison with their results we find that the duality between gluon amplitudes and Wilson loops is preserved. This review is based on the aut...

Henn, J M

2006-08-07

377

Evaluation of transient amplitudes between Dirac spinors  

Energy Technology Data Exchange (ETDEWEB)

The authors present a simple method for expressing transition amplitudes between fermion states of definite polarization in terms of momenta and polarization vectors only, rather than ..gamma..-matrices and spinors. As an illustration, Coulomb and Bhabha scattering for polarized particles is evaluated.

Caffo, M. (European Organization for Nuclear Research, Geneva (Switzerland)); Remiddi, E. (Geneva Univ. (Switzerland). Inst. de Physique Theorique)

1983-01-10

378

Evaluating Real Time Finite Temperature Feynman Amplitudes  

CERN Document Server

We construct a program to calculate Feynman amplitudes at finite temperature in the real time Keldysh formalism using the symbolic manipulation program {\\it Mathematica}. As an example, the usefulness of this program is demonstrated by proving the finite temperature Ward identity for QED in a second order effective theory.

Carrington, M E; Hachkowski, A; Pickering, D; Sowiak, J C; Defu, Hou

2000-01-01

379

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

380

Simplifying the three point type I amplitude  

International Nuclear Information System (INIS)

Full text: The superstring theory is the most promising model of the last decades for unifying all interactions of nature. Besides its importance, a covariant approach of quantization was an unsolved problem for a long time, until the development of the pure spinor formalism. In a previous work the type I effective action for supergravity was computed in this framework . In that work, the tree-level mixed amplitudes (for one closed string and two open strings) were computed. Roughly speaking, the basic steps followed in that analysis were: 1) write the amplitude involving the three vertex operators needed in the computation,2) use the cyclic symmetry to choose one closed and one open strings as fixed operators, 3) Simplify it by using OPE's inside the amplitude and 4), for the remaining terms, evaluate all combinations (term by term) with five theta's. For example, in step number 4, in order to make all necessary calculations, the GAMMA package (a program for MATHEMATICA) had to be used to evaluate products of gamma matrices inside the amplitude. The fact is that there is an important tool that have the power to simplify more these calculations: the cyclic symmetry prescription. It means that, no matter the three unintegrated vertex are, the result is the same for all possibilities you get. In this work we use this symmetry in the three point amplitude for choose the fermion operators as the unintegrated ones. This simplifies the computations in such a way that no program is needed to find the right result, what gives a cleaner result. (author)

2011-01-01

 
 
 
 
381

A Solid-State Modulator for High Speed Kickers  

Energy Technology Data Exchange (ETDEWEB)

An all solid-state modulator with multi-pulse burst capability, very fast rise and fall times, pulse width agility, and amplitude modulation capability for use with high-speed beam kickers has been designed and tested at LLNL. The modulator uses multiple solid-state modules stacked in an inductive-adder configuration. It provides a nominal 18kV pulse with {+-} 10% amplitude modulation on the order of several MHz, rise times on the order of 10nS, and can be configured for either positive or negative polarity. The presentation will include measured performance data.

Watson, J A; Cook, E G; Chen, Y J; Anaya, R M; Lee, B S; Sullivan, J S; Hawkins, S A; Allen, F V; Hickman, B C; Brooksby, C A

2001-06-11

382

High-energy amplitudes in N=4 SYM in the next-to-leading order  

International Nuclear Information System (INIS)

The high-energy behavior of the N=4 SYM amplitudes in the Regge limit can be calculated order by order in perturbation theory using the high-energy operator expansion in Wilson lines. At large Nc, a typical four-point amplitude is determined by a single BFKL pomeron. The conformal structure of the four-point amplitude is fixed in terms of two functions: pomeron intercept and the coefficient function in front of the pomeron (the product of two residues). The pomeron intercept is universal while the coefficient function depends on the correlator in question. The intercept is known in the first two orders in coupling constant: BFKL intercept and NLO BFKL intercept calculated in Ref. 1. As an example of using the Wilson-line OPE, we calculate the coefficient function in front of the pomeron for the correlator of four Z2 currents in the first two orders in perturbation theory.

2010-04-01

383

Modulated TEA laser receiver  

Energy Technology Data Exchange (ETDEWEB)

A receiver is for receiving information modulated onto the output of a pulsed TEA laser. The output has an envelope shape including a relatively short and high-amplitude pulse portion followed by a relatively long and low-amplitude tail portion, whereby the information is amplitude-modulated onto the tail. The receiver includes: a photodetector responsive to the output of the laser, having a high-sensitivity state and a low-sensitivity state, and having an output; means for switching the photodetector between the states, whereby the photodetector is in the low-sensitivity state in the absence of an output from the laser and during the pulse portion, and in the high-sensitivity state during the tail portion; and energizable means for demodulating the output of the photodetector. The means for switching includes means for biasing the photodetector to the low-sensitivity state and means responsive to the output of the photodetector during the pulse portion of the laser output.

Nomiyama, N.T.; Rohde, R.S.; Buser, R.G.

1986-12-09

384

Kinematic Numerators and a Double-Copy Formula for N = 4 Super-Yang-Mills Residues  

CERN Document Server

Recent work by Cachazo, He, and Yuan shows that connected prescription residues obey the global identities of N = 4 super-Yang-Mills amplitudes. In particular, they obey the Bern-Carrasco-Johansson (BCJ) amplitude identities. Here we offer a new way of interpreting this result via objects that we call residue numerators. These objects behave like the kinematic numerators introduced by BCJ except that they are associated with individual residues. In particular, these new objects satisfy a double-copy formula relating them to the residues appearing in recently-discovered analogs of the connected prescription integrals for N = 8 supergravity. Along the way, we show that the BCJ amplitude identities are equivalent to the consistency condition that allows kinematic numerators to be expressed as amplitudes using a generalized inverse.

Litsey, Sean

2013-01-01

385

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Frequency modulation upon nonstationary heating of the p - n junction in high-sensitive diode laser spectroscopy  

Science.gov (United States)

A special type of modulation of the injection current of a diode laser is proposed at which the frequency modulation of radiation is not accompanied by the residual amplitude modulation. This method considerably reduces the influence of the diode laser radiation instability on the recorded absorption spectra. This allows a prolonged monitoring of small amounts of impurities in gas analysis by retaining a high sensitivity. Prolonged measurements of absorption spectra are performed at a relative absorption of 8×10-7. By using a 50-cm multipass cell with the optical length of 90 m, the absorption coefficient of 1.2×10-10 cm-1 was detected. As an example, the day evolution of the background concentrations of NO2 molecules was measured in the atmosphere.

Andreev, Sergei N.; Nikolaev, I. V.; Ochkin, Vladimir N.; Savinov, Sergei Yu; Spiridonov, Maksim V.; Tskhai, Sergei N.

2007-04-01

386

Constructing QCD one-loop amplitudes  

Energy Technology Data Exchange (ETDEWEB)

In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 {var_epsilon}. The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally other new methods have also proved fruitful for calculating rational terms [8]. Such developments have again refocused attention on the optimization of the derivation of the cut-constructable pieces of the amplitude. Deriving cut-constructible terms for any one-loop amplitude reduces to the computation of coefficients of a set of scalar bubble, scalar triangle and scalar box integral functions. Box coefficients may be found with very little work, directly from the quadruple cut of the relevant box function [9]. A unique box coefficient contributes to each distinct quadruple cut. Unfortunately triangle and bubble coefficients cannot be derived in quite so direct a manner. Multiple scalar integral coefficients appear inside a two-particle cut or triple cut. It is therefore necessary to disentangle the relevant bubble or triangle coefficients from any other coefficients sharing the same cut [1, 4, 10, 11]. The large number of NLO processes of interest for the LHC suggests that a completely automated computational procedure is highly desired. To this end we discuss, in this proceeding, a recently proposed method [12, 13] for the direct, efficient and systematic extraction of bubble and triangle coefficients which is well suited to automation.

Forde, Darren; /SLAC /UCLA

2008-02-22

387

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)

1989-12-05

388

Optical twists in phase and amplitude  

DEFF Research Database (Denmark)

Light beams with helical phase profile correspond to photons having orbital angular momentum (OAM). A Laguerre-Gaussian (LG) beam is an example where its helical phase sets a phase-singularity at the optical axis and forms a ring-shaped transverse amplitude profile. Here, we describe a unique beam where both phase and amplitude express a helical profile as the beam propagates in free space. Such a beam can be accurately referred to as an optical twister. We characterize optical twisters and demonstrate their capacity to induce spiral motion on particles trapped along the twisters’ path. Unlike LG beams, the far field projection of the twisted optical beam maintains a high photon concentration even at higher values of topological charge. Optical twisters have therefore profound applications to fundamental studies of light and atoms such as in quantum entanglement of the OAM, toroidal traps for cold atoms and for optical manipulation of microscopic particles.

Daria, Vincent R.; Palima, Darwin

2011-01-01

389

Twistor-strings and gravity tree amplitudes  

CERN Document Server

Recently we proposed that the original Berkovits-Witten twistor-string theory could be used to compute Einstein supergravity tree amplitudes. Subsequently remarkable formulae for the MHV amplitudes were found by Hodges and generalized to N^{k}MHV by Cachazo and Skinner. Here we show how the Hodges matrix and its higher MHV degree generalization can be understood as arising from the twistor-string formula. In particular we see that if loops are allowed in the worldsheet correlators, the wrong answers are obtained. On the other hand the Hodges matrix and its generalizations arise when only connected trees are allowed by using the Matrix-Tree theorem to sum up the Feynman diagrams for the worldsheet correlators in the twistor-string theory. Other ingredients in these formulae remain to be properly understood within the twistor-string theory approach.

Adamo, Tim

2012-01-01

390

Semiconducter Optical Amplifier as a Phase Modulator for Coherent Laser Radar (Preprint).  

Science.gov (United States)

We investigate the use of a saturated semiconductor optical amplifier as a phase modulator for long range laser radar applications. The nature of the phase and amplitude modulation resulting from saturating in amplifier with a high peak power Gaussian pul...

B. Duncan J. Carns M. Dierking

2012-01-01

391

Accommodative amplitude required for sustained near work.  

UK PubMed Central (United Kingdom)

PURPOSE: Many practitioners base the prescription of near vision additions on the assertion that only one half or two-thirds of an individual's amplitude of accommodation is sustainable for a prolonged period. To better understand how much eye focus needs to be restored for presbyopic corrections to be adequate, this study investigated the robustness of the pre-presbyopic human accommodative system during a sustained and intensive near vision task. METHODS: Twenty-one pre-presbyopic volunteers (aged 26.1?±?4.7 years) participated in the study. Binocular subjective amplitude of accommodation was measured before and after a prolonged reading exercise, using the RAF rule. During the 30 min reading task, the subject's closest comfortable eye-to-text distance and pupil size was monitored. Accommodative accuracy to 0.2, 1.0, 2.0, 3.0 and 4.0 D stimuli was determined objectively using a validated binocular open-view autorefractor immediately before, and after the reading task. RESULTS: Amplitude of accommodation (p=0.09) and accommodative accuracy (p>0.05) were statistically unchanged following the intensive near task. The mean proportion of accommodation exerted throughout the near exercise was 80.6% (range 45.3?±?3.7 to 96.6?±?4.3%), which increased as the task progressed (F=2.24, p=0.02). The mean percentage of accommodation utilised increased with subject age (r=0.517, p = 0.016). CONCLUSION: The pre-presbyopic human accommodative system is robust to fatigue during intense and prolonged near work. A greater proportion of one's amplitude of accommodation may be continuously exerted than previously suggested.

Wolffsohn JS; Sheppard AL; Vakani S; Davies LN

2011-09-01

392

High amplitude mode and DNA opening  

Science.gov (United States)

In this article, we define and analyse an extremely high amplitude (EHA) mode in DNA dynamics. The dynamics of a DNA chain is described by the Peyrard-Bishop-Dauxois model. We show that a local opening of the DNA chain in a process of m-RNA transcription is the EHA behaviour. Also, we point out that the helicoidal structure brings about the possibility for the EHA mode to occur.

Zdravkovic, S.; Sataric, M. V.

2007-05-01

393

Amplitude discriminators with variable hysteresis voltage  

International Nuclear Information System (INIS)

A variation in the hysteresis voltage proportional to the threshold of an integrated discriminator of a pulse amplitude results in it having a higher noise immunity. The discriminator threshold voltage varies between 20 mV and 5.1 V with an increment of 20 mV. The output signal settles in less than 50 nsec. The threshold-voltage temperature drift in 50 ?V/degrees C

1994-01-01

394

Nucleon and $N^* (1535)$ Distribution Amplitudes  

CERN Multimedia

The QCDSF collaboration has investigated the distribution amplitudes and wavefunction normalization constants of the nucleon and its parity partner, the $N^* (1535)$. We report on recent progress in the calculation of these quantities on configurations with two dynamical flavors of $\\mathcal{O}(a)$-improved Wilson fermions. New data at pion masses of approximately 270 MeV helps in significantly reducing errors in the extrapolation to the physical point.

Braun, V M; Göckeler, M; Hagen, C; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schäfer, A; Schiel, R W; Schierholz, G; Stüben, H; Zanotti, J M

2010-01-01

395

Deep Inelastic Scattering at the Amplitude Level  

Energy Technology Data Exchange (ETDEWEB)

The deep inelastic lepton scattering and deeply virtual Compton scattering cross sections can be interpreted in terms of the fundamental wavefunctions defined by the light-front Fock expansion, thus allowing tests of QCD at the amplitude level. The AdS/CFT correspondence between gauge theory and string theory provides remarkable new insights into QCD, including a model for hadronic wavefunctions which display conformal scaling at short distances and color confinement at large distances.

Brodsky, Stanley J.; /SLAC

2005-08-04

396

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

397

On the infinities of closed superstring amplitudes  

Energy Technology Data Exchange (ETDEWEB)

The authors present an analysis of possible infinities that may be present in uncompactified multi-loop heterotic and type II superstring amplitudes constructed, without use of the short-string limit, in the light-cone gauge, and with use of a closed (10)-SUSY field theory algebra. Various types of degenerations of the integrand are discussed on the string worldsheet. No infinities are found, modulo (for type II) a particular identity for Green's functions.

Restuccia, A.; Taylor, J.G.

1988-08-01

398

On the infinities of closed superstring amplitudes  

International Nuclear Information System (INIS)

[en] We present an analysis of possible infinities that may be present in uncompactified multi-loop heterotic and type II superstring amplitudes constructed, without use of the short-string limit, in the light-cone gauge, and with use of a closed SUSY field theory algebra. Various types of degenerations of the integrand are discussed on the string world-sheet. No infinities are found, modulo (for type II) a particular identity for Green's functions. (author). 13 refs

1987-01-01

399

A note on Coulomb scattering amplitude  

CERN Document Server

The summation of the partial wave series for Coulomb scattering amplitude, $f^C(\\theta)$ is avoided because the series is oscillatorily and divergent. Instead, $f^C(\\theta)$ is obtained by solving the Schr{\\"o}dinger equation in parabolic cylindrical co-ordinates which is not a general method. Here, we show that a reconstructed series, $(1-\\cos\\theta) ^2f^C(\\theta)$, is both convergent and analytically summable.

Ahmed, Z

2003-01-01

400

Transversity Amplitudes in Hypercharge Exchange Processes  

International Nuclear Information System (INIS)

' In this work we present several techniques developed for the extraction of the. Transversity amplitudes governing quasi two-body meson baryon reactions with hypercharge exchange. We review the methods used in processes having a pure spin configuration, as well as the more relevant results obtained with data from Kp and Tp interactions at intermediate energies. The predictions of the additive quark model and the ones following from exchange degeneracy and etoxicity are discussed. We present a formalism for amplitude analysis developed for reactions with mixed spin configurations and discuss the methods of parametric estimation of the moduli and phases of the amplitudes, as well as the various tests employed to check the goodness of the fits. The calculation of the generalized joint density matrices is given and we propose a method based on the generalization of the idea of multipole moments, which allows to investigate the structure of the decay angular correlations and establishes the quality of the fits and the validity of the simplifying assumptions currently used in this type of studies. (Author) 43 refs.

1979-01-01

 
 
 
 
401

ABJM amplitudes and the positive orthogonal grassmannian  

CERN Multimedia

A remarkable connection between perturbative scattering amplitudes of four-dimensional planar SYM, and the stratification of the positive grassmannian, was revealed in the seminal work of Arkani-Hamed et. al. Similar extension for three-dimensional ABJM theory was proposed. Here we establish a direct connection between planar scattering amplitudes of ABJM theory, and singularities there of, to the stratification of the positive orthogonal grassmannian. In particular, scattering processes are constructed through on-shell diagrams, which are simply iterative gluing of the fundamental four-point amplitude. Each diagram is then equivalent to the merging of fundamental OG_2 orthogonal grassmannian to form a larger OG_k, where 2k is the number of external particles. The invariant information that is encoded in each diagram is precisely this stratification. This information can be easily read off via permutation paths of the on-shell diagram, which also can be used to derive a canonical representation of OG_k that m...

Huang, Yu-tin

2013-01-01

402

A proposed proper EPRL vertex amplitude  

CERN Multimedia

As established in a prior work of the author, the linear simplicity constraints used in the construction of the so-called `new' spin-foam models mix three of the five sectors of Plebanski theory, only one of which is gravity in the usual sense, and this is the reason for certain `unwanted' terms in the asymptotics of the EPRL vertex amplitude as calculated by Barrett et al. In the present paper, an explicit classical discrete condition is derived that isolates the desired gravitational sector, which we call (II+), following other authors. This condition is quantized and used to modify the vertex amplitude, yielding what we call the `proper EPRL vertex amplitude.' This vertex still depends only on standard SU(2) spin-network data on the boundary, is SU(2) gauge invariant, and is linear in the boundary state, as required. In addition, the asymptotics now consist in the single desired term of the form $e^{iS_{\\Regge}}$, and all degenerate configurations are exponentially suppressed.

Engle, Jonathan

2011-01-01

403

Mellin Amplitudes for Dual Conformal Integrals  

CERN Multimedia

Motivated by recent work on the utility of Mellin space for representing conformal correlators in $AdS$/CFT, we study its suitability for representing dual conformal integrals of the type which appear in perturbative scattering amplitudes in super-Yang-Mills theory. We discuss Feynman-like rules for writing Mellin amplitudes for a large class of integrals in any dimension, and find explicit representations for several familiar toy integrals. However we show that the power of Mellin space is that it provides simple representations even for fully massive integrals, which except for the single case of the 4-mass box have not yet been computed by any available technology. Mellin space is also useful for exhibiting differential relations between various multi-loop integrals, and we show that certain higher-loop integrals may be written as integral operators acting on the fully massive scalar $n$-gon in $n$ dimensions, whose Mellin amplitude is exactly 1. Our chief example is a very simple formula expressing the 6-...

Paulos, Miguel F; Volovich, Anastasia

2012-01-01

404

Tree-level (?,K) amplitude and analyticity  

International Nuclear Information System (INIS)

[en] I consider the tree-level amplitude describing all three channels of the binary (?,K) reaction, as a meromorphic, polynomially bounded function of three dependent complex variables. Using the Mittag-Leffler theorem, I construct three convergent partial fraction expansions, each one being applied in the corresponding domain. Noting that the mutual intersections of those domains are nonempty, I employ analytical continuation. It is shown that the necessary conditions to make such a continuation feasible are the following: (1) The only parameters completely determining the amplitude are the on-shell couplings and masses; (2) these parameters are restricted by a certain (infinite) system of bootstrap equations; (3) the full cross-symmetric amplitude takes the dual form even when the Pomeron contribution is taken into account; (4) this latter contribution corresponds to a nonresonant background which, in turn, is expressed in terms of cross-channel resonance parameters. Also, it is demonstrated that chiral symmetry provides a unique scale for the mentioned parameters, the resonance saturation effect appearing as a direct consequence of the above results. copyright 1997 The American Physical Society

1997-01-01

405

High CW power, phase and amplitude modulatorrealized with fast ferrite phase-shifters  

CERN Document Server

Superconducting cavity resonators are suffering from detuning effects caused by high internal electromagnetic fields (Lorentz force detuning). For classical resonators working with continuous wave signals, this detuning is static and compensated by the slow mechanical tuning system. However, pulsing of superconducting cavities, an operational mode only recently considered, results in dynamic detuning effects. New ways to handle this effect have to be found and worked out. A way to supply several superconducting cavities in the particle accelerator by one large transmitter while keeping the possibility of controlling the field in each individual cavity is shown. By introducing a fast phase and amplitude modulator into each cavity feeder line, the individual deviations of each cavity with respect to the average can be compensated in order to equalize their behaviour for the main control loop, which will compensate the global detuning of all cavities. Several types of phase and amplitude modulators suitable for ...

Valuch, D

2004-01-01

406

Crack propagation under variable amplitude loading  

Scientific Electronic Library Online (English)

Full Text Available 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 propagation 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. I (more) t 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.

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

2013-10-01

407

Crack propagation under variable amplitude loading  

Scientific Electronic Library Online (English)

Full Text Available 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 propagation 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. I (more) t 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.

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

2013-01-01

408

Properties of large-amplitude internal waves  

Science.gov (United States)

Properties of solitary waves propagating in a two-layer fluid are investigated comparing experiments and theory. In the experiments the velocity field induced by the waves, the propagation speed and the wave shape are quite accurately measured using particle tracking velocimetry (PTV) and image analysis. The experiments are calibrated with a layer of fresh water above a layer of brine. The depth of the brine is 4.13 times the depth of the fresh water. Theoretical results are given for this depth ratio, and, in addition, in a few examples for larger ratios, up to 100[ratio]1. The wave amplitudes in the experiments range from a small value up to almost maximal amplitude. The thickness of the pycnocline is in the range of approximately 0.13 0.26 times the depth of the thinner layer. Solitary waves are generated by releasing a volume of fresh water trapped behind a gate. By careful adjustment of the length and depth of the initial volume we always generate a single solitary wave, even for very large volumes. The experiments are very repeatable and the recording technique is very accurate. The error in the measured velocities non-dimensionalized by the linear long wave speed is less than about 7 8% in all cases. The experiments are compared with a fully nonlinear interface model and weakly nonlinear Korteweg de Vries (KdV) theory. The fully nonlinear model compares excellently with the experiments for all quantities measured. This is true for the whole amplitude range, even for a pycnocline which is not very sharp. The KdV theory is relevant for small wave amplitude but exhibit a systematic deviation from the experiments and the fully nonlinear theory for wave amplitudes exceeding about 0.4 times the depth of the thinner layer. In the experiments with the largest waves, rolls develop behind the maximal displacement of the wave due to the Kelvin Helmholtz instability. The recordings enable evaluation of the local Richardson number due to the flow in the pycnocline. We find that stability or instability of the flow occurs in approximate agreement with the theorem of Miles and Howard.

Grue, John; Jensen, Atle; Rusås, Per-Olav; Sveen, J. Kristian

1999-02-01

409

Synchronous amplitude and time control for an optimum dynamic range variable photonic delay line.  

UK PubMed Central (United Kingdom)

A synchronous-amplitude-controlled and time-delay-controlled photonic controller for phased-array antenna applications is proposed and demonstrated. Amplitude control is based on a variable optical attenuator system that operates in synchronism with the photonic delay line (PDL). This amplitude control system can provide both the signal calibration for the different PDL channels and settings required for driving the antenna elements of a phased-array radar and the optimum optical power levels that impinge on the photodetector for optimum fiber-optic-link performance. Various variable amplitude control modules based on ferroelectric liquid crystals, polymer-dispersed liquid crystals, and photoconductive devices are proposed. We show that the dynamic range loss due to a switched-PDL inherent structure loss can be compensated when we control the optical power from the laser, using the synchronous optical attenuation system. For the first time to our knowledge, full dynamic range loss compensation is demonstrated for an external-modulation-fed 3-bit switched PDL with a structure optical insertion loss of 5.5 dB. A compression dynamic range of 158 dBxHz was measured at 6 GHz, and a spurious free dynamic range of 111 dBxHz(2/3) was estimated. Feasibility of the dynamic range compensation technique for multichannel, higher-insertion-loss PDL systems is discussed.

Riza NA; Madamopoulos N

1999-04-01

410

Temporal dynamics of convergent modulation at a crustacean neuromuscular junction.  

UK PubMed Central (United Kingdom)

At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and -allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and allatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and -allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; -allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation-contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude.

Jorge-Rivera JC; Sen K; Birmingham JT; Abbott LF; Marder E

1998-11-01

411

Temporal dynamics of convergent modulation at a crustacean neuromuscular junction.  

Science.gov (United States)

At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and -allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and allatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and -allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; -allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation-contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude. PMID:9819263

Jorge-Rivera, J C; Sen, K; Birmingham, J T; Abbott, L F; Marder, E

1998-11-01

412

Pseudophakic residual astigmatism.  

Science.gov (United States)

We investigated pseudophakic residual astigmatism in order to minimize postoperative refractive astigmatism. We examined 110 eyes of 87 patients who had undergone phacoemulsification with small incision and posterior chamber intraocular lens (IOL) implantation. Corneal astigmatism was measured using an autokeratometer (RK-5, canon), refractive astigmatism by manifest refraction, and residual astigmatism by vector analysis. Mean pseudophakic residual astigmatism was +0.47 x 176 degrees, predominantly against-the-rule. Variations of pseudophakic residual astigmatism according to sex, age and IOL type were not statistically significant. When performing cataract surgery as refractive surgery, we may consider that pseudophakic residual astigmatism is approximately 0.50D against-the-rule. PMID:15635824

Bae, Jung Gn; Kim, Sung Jin; Choi, Young In

2004-12-01

413

Pseudophakic residual astigmatism.  

UK PubMed Central (United Kingdom)

We investigated pseudophakic residual astigmatism in order to minimize postoperative refractive astigmatism. We examined 110 eyes of 87 patients who had undergone phacoemulsification with small incision and posterior chamber intraocular lens (IOL) implantation. Corneal astigmatism was measured using an autokeratometer (RK-5, canon), refractive astigmatism by manifest refraction, and residual astigmatism by vector analysis. Mean pseudophakic residual astigmatism was +0.47 x 176 degrees, predominantly against-the-rule. Variations of pseudophakic residual astigmatism according to sex, age and IOL type were not statistically significant. When performing cataract surgery as refractive surgery, we may consider that pseudophakic residual astigmatism is approximately 0.50D against-the-rule.

Bae JG; Kim SJ; Choi YI

2004-12-01

414

Use of the delta-t method for setting rf phase and amplitude for the AHF linac  

Energy Technology Data Exchange (ETDEWEB)

The delta-t procedure is a time-of-flight method of finding set points for the rf phase and amplitude for each module of a linac. Expected errors for LAMPF afterburner linacs which might be used for an advanced hadron facility (AHF) are calculated. The modified delta-t procedure used on modules 13 through 48 of the present linac appears adequate to set up the proposed AHF linacs. 24 refs., 7 figs., 1 tab.

Swain, G.R.

1989-01-01

415

Pion distribution amplitude within the instanton model  

International Nuclear Information System (INIS)

[en] The leading-twist pion distribution amplitude is obtained at a low normalization scale of an order of the inverse average size of an instanton ?c. The pion dynamics, consistent with gauge invariance and low energy theorems, is considered within the instanton vacuum model. The results are QCD evolved to higher momentum-transfer values, and are in agreement with recent data from CLEO on pion transition form factor. We also show that previous calculations violate the axial Ward-Takahashi identity

1999-01-01

416

Impact Representation of Generalized Distribution Amplitudes  

CERN Multimedia

We develop an impact representation for the generalized distribution amplitude which describes the exclusive hadronization of a quark-antiquark pair to a pair of mesons. Experiments such as gamma^* gamma -> pi pi and gamma^* N -> pi pi N' are shown to probe the transverse size of the hadronization region of the quark antiquark pair that one can interpret as the transverse overlap of the two emerging mesons. An astonishing feature of this description is that low energy pi pi phase shift analysis can be used for understanding some properties of quark hadronization process.

Pire, B

2003-01-01

417

Analytic amplitude models for forward scattering  

CERN Multimedia

We report on fits of a large class of analytic amplitude models for forward scattering against the comprehensive data for all available reactions. To differentiate the goodness of the fits of many possible parametrizations to a large sample of data, we developed and used a set of quantitative indicators measuring statistical quality of the fits over and beyond the typical criterion of the $\\Chi^2 /dof$. These indicators favor models with a universal $ log^2 s$ Pomeron term, which enables one to extend the fit down to $\\sqrt s = 4$ GeV.

Kang, K; Ezhela, Vladimir V; Gauron, P; Kuyanov, Yu V; Lugovsky, S B; Nicolescu, Basarab; Tkachenko, N P; Kuyanov, Yu. V.

2002-01-01

418

Semiclassical scattering amplitudes of dressed gravitons  

CERN Multimedia

We consider effective action for the Einstein gravity and show that dressed mean fields are actual variables of the effective action. Kernels of this effective action expressed in terms of dressed effective fields are constituent parts of scattering amplitudes for gravitons. Possible applications to the graviton scattering and black hole formation are discussed at the semiclassical level. In particular, we consider graviton scattering in four dimensions based on the Lipatov effective action for quantum gravity, shock waves of particles moving on the brane in Randall-Sundrum scenario with fifth extra dimension, and Giddings' estimation of Froissart bound.

Kang, K; Kang, Kyungsik; Kondrashuk, Igor

2004-01-01

419

Information transfer with small-amplitude signals  

CERN Multimedia

We study the optimality conditions of information transfer in systems with memory in the low signal-to-noise ratio regime of vanishing input amplitude. We find that the optimal mutual information is represented by a maximum-variance of the signal time course, with correlation structure determined by the Fisher information matrix. We provide illustration of the method on a simple biologically-inspired model of electro-sensory neuron. Our general results apply also to the study of information transfer in single neurons subject to weak stimulation, with implications to the problem of coding efficiency in biological systems.

Kostal, Lubomir; 10.1103/PhysRevE.81.050901

2010-01-01

420

Higher Order Cummulants based Digital Modulation Recognition Scheme  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we have presented that Higher Order Cummulants (HOC) based modulation recognition scheme for Pulse Amplitude Modulation (PAM), Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK) modulated signals having orders of 2 to 64. Modulation recognition is a process to recognize the signal modulation type which is received by the receiver in the presence of channel noise. The HOC based MR is accomplished in two modules. First is feature extraction using higher order cummulants. These features are distinct for different modulated signals. Second is recognition process which gives decision based upon the features extracted from higher order cummulants. The Probability of Correctness (POC) curves shows the recognition accuracy for sample size and number of iterations. The Additive White Gaussian Noise (AWGN) is considered throughout the simulations.

Sajjad Ahmed Ghauri; Ijaz Mansoor Qureshi; Aqdas Naveed Malik; Tanveer Ahmed Cheema

2013-01-01

 
 
 
 
421

Multi-amplitude Differential Space-time Block Coding Scheme for Square/Non-Square Code Matrix in MIMO Systems  

Directory of Open Access Journals (Sweden)

Full Text Available Differential space-time coding (DSTC) technique has become a good choice when channel estimations are difficult to obtain in multiple antennas system. On the basis of analyzing the existing DSTC schemes, by introducing multi-level quadrature amplitude modulation (MQAM) and matrix transform method, we develop a multi-amplitude differential space-time block coding (STBC) scheme for square or non-square code matrix in MIMO systems, and give the derivation of calculation formulae of the coding advantage in detail. The developed scheme can effectively avoid the performance loss of conventional DSTC schemes based on PSK modulation (i.e. single amplitude DSTC) in high spectrum efficiency. It can be applied to non-square code matrix case, and thus overcomes the shortcoming that existing DSTC schemes are only suitable for square code matrix. Compared with single amplitude DSTC schemes, our scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes. Moreover, our scheme has linear decoding complexity, higher coding advantage, and higher code rate for more than two antennas. The simulations results show that the proposed scheme can provide lower BER than the existing single amplitude differential STBC schemes for both square and non-square code matrices.

Xiangbin Yu; Xiaomin Chen; Yuyu Xin; Qiuming Zhu; Dazhuan Xu

2012-01-01

422

Differential Equations for Feynman Graph Amplitudes  

CERN Multimedia

It is by now well established that, by means of the integration by part identities, all the integrals occurring in the evaluation of a Feynman graph of given topology can be expressed in terms of a few independent master integrals. It is shown in this paper that the integration by part identities can be further used for obtaining a linear system of first order differential equations for the master integrals themselves. The equations can then be used for the numerical evaluation of the amplitudes as well as for investigating their analytic properties, such as the asymptotic and threshold behaviours and the corresponding expansions (and for analytic integration purposes, when possible). The new method is illustrated through its somewhat detailed application to the case of the one loop self-mass amplitude, by explicitly working out expansions and quadrature formulas, both in arbitrary continuous dimension n and in the n \\to 4 limit. It is then shortly discussed which features of the new method are expected to wo...

Remiddi, E

1997-01-01

423

Association between accommodative amplitudes and amblyopia.  

UK PubMed Central (United Kingdom)

PURPOSE: To evaluate the relationship between amblyopia and accommodative ability. METHODS: The open-field Grand Seiko binocular autorefractor has become the gold standard for automated measurement of static accommodation. We measured the accommodation amplitudes in 52 children ages 3 to 14 years employing the Grand Seiko auto refractor. Children wore their glasses for this test, which was prescribed based on a cycloplegic refraction performed by one pediatric ophthalmologist. No readings could be obtained for 9 eyes (5 patients). RESULTS: Normal accommodation with correction utilizing full accommodative effort at 1/3 meter is 3D assuming no accommodative lag, and would generate a reading of -3.00D from the Grand Seiko auto refractor. Lack of any accommodative should give a reading of 0.00D. Accommodative gradually declined as the acuity worsened. CONCLUSION: Our results suggest that amblyopic eyes do not accommodate as well as non-amblyopic eyes. Because accommodation amplitude is not subjective it may be a more sensitive indicator of regression of amblyopia than visual acuity. The Grand Seiko autorefractor could prove to be a useful tool to monitor the progress of patients with amblyopia.

Singman E; Matta N; Tian J; Silbert D

2013-06-01

424

The Construction of Spin Foam Vertex Amplitudes  

CERN Document Server

Spin foam vertex amplitudes are the key ingredient of spin foam models for quantum gravity. They fall into the realm of discretized path integral, and can be seen as generalized lattice gauge theories. They can be seen as an attempt at a 4 dimensional generalization of the Ponzano-Regge model for 3d quantum gravity. We motivate and review the construction of the vertex amplitudes of recent spin foam models, giving two different and complementary perspectives of this construction. The first proceeds by extracting geometric configurations from a topological theory of the BF type, and can be seen to be in the tradition of the work of Barret and Crane and Freidel and Krasnov. The second keeps closer contact to the structure of Loop Quantum Gravity and tries to identify an appropriate set of constraints to define a Lorentz-invariant interaction of its quanta of space. This approach is in the tradition of the work of Smolin, Markopoulous, Engle, Pereira, Rovelli and Livine.

Bianchi, Eugenio

2012-01-01

425

The Construction of Spin Foam Vertex Amplitudes  

Directory of Open Access Journals (Sweden)

Full Text Available Spin foam vertex amplitudes are the key ingredient of spin foam models for quantum gravity. These fall into the realm of discretized path integral, and can be seen as generalized lattice gauge theories. They can be seen as an attempt at a 4-dimensional generalization of the Ponzano-Regge model for 3d quantum gravity. We motivate and review the construction of the vertex amplitudes of recent spin foam models, giving two different and complementary perspectives of this construction. The first proceeds by extracting geometric configurations from a topological theory of the BF type, and can be seen to be in the tradition of the work of Barrett, Crane, Freidel and Krasnov. The second keeps closer contact to the structure of Loop Quantum Gravity and tries to identify an appropriate set of constraints to define a Lorentz-invariant interaction of its quanta of space. This approach is in the tradition of the work of Smolin, Markopoulous, Engle, Pereira, Rovelli and Livine.

Eugenio Bianchi; Frank Hellmann

2013-01-01

426

Small-amplitude synchrotron tune near transition  

Energy Technology Data Exchange (ETDEWEB)

The separatrices of the rf buckets near transition are mapped when the synchronous phase is neither 0 or {pi}. The small-amplitude synchronous tune is derived when the rf frequency is changed. Synchrotron radiation is present in all electron storage ring. As a result, the synchronous phase is always offset from {phi}{sub s} = {pi} to compensate for the power loss. Even for proton storage rings with negligible synchrotron radiation, the synchronous phase is also required to be offset from {phi}{sub s} = 0 or {pi} slightly to compensate for beam loading. Thus for all storage rings operating near transition, beam particles reside in accelerating buckets instead of stationary bucket. It is of interest to map these buckets and see how they evolve near transition. When the rf frequency is varied, the closed orbit is pushed radially inward or outward. The momentum of the particle synchronous with the rf is thus changed. By measuring the small-amplitude synchrotron tune as a function of the rf frequency, the lowest first few orders of the slip factor can be inferred. Here, we derive this relationship up to the lowest first three orders of the slip factor when the particle velocity is not ultra-relativistic.

Ng, K.Y.; /Fermilab

2010-05-01

427

What shapes pulse amplitude of intracranial pressure?  

Science.gov (United States)

The pulsatile component of intracranial pressure (ICP) has been shown to be a predictor of outcome in normal pressure hydrocephalus (NPH) and traumatic brain injury (TBI). Experimental studies have demonstrated that the pulse amplitude of ICP (AMP(ICP)) is dependent on the mean ICP (mICP), and on the pulse amplitude of the cerebral arterial blood volume (AMP(CaBV)), according to the exponential craniospinal compliance curve. In this study, we compared the influence of mICP and AMP(CaBV) on AMP(ICP) in patients with NPH (infusion study) and TBI (spontaneous recording). We retrospectively analyzed 25 NPH and 43 TBI patients with continuous monitoring of ICP and cerebral blood flow velocity (CBFV), as assessed with transcranial doppler. AMP(CaBV) was extracted from the CBFV waveform. The influence of mICP and AMP(CaBV) on AMP(ICP) were determined using partial coefficients a, b, and c of the multiple regression model: AMP(ICP) = a * mICP + b * AMP(CaBV) + c. AMP(ICP) was more dependent on mICP in NPH patients than in TBI patients (partial coefficient a = 0.93 versus -0.03; p mICP in TBI and NPH patients. PMID:19852586

Carrera, Emmanuel; Kim, Dong-Joo; Castellani, Gianluca; Zweifel, Christian; Czosnyka, Zofia; Kasparowicz, Magdalena; Smielewski, Peter; Pickard, John D; Czosnyka, Marek

2010-02-01

428

Versatile offset-free 16-QAM single dual-drive IQ modulator driven by binary signals.  

UK PubMed Central (United Kingdom)

A customized IQ modulator driven by equal-amplitude binary signals for generating offset-free 16-quadrature amplitude modulation (QAM) is proposed and validated through simulations. The incorporation of tunable splitters demonstrates the feasibility of the transmitter and enables more efficient constellations such as hexagonal 16-QAM.

Malacarne A; Fresi F; Klamkin J; Potì L

2012-10-01

429

IGBT modules; IGBT module  

Energy Technology Data Exchange (ETDEWEB)

Described are the NPT (Non-Punch-Through)-IGBT and high-voltage IGBT for use aboard vehicles developed by Fuji Electric Co., Ltd., for application of IGBT modules under higher-voltage larger-capacity environments. The loss to occur when an IGBT is applied to an inverter consists of the steady loss and switching loss. During the development of the NPT-IGBT, an optimized production technology was established for improvement on the loss feature, by which the chip may be made thinner without deterioration in the voltage withstanding capability. The 1400V NPT-IGBT introduced here incurs a total loss equal to what is expected from a 1200V PT (Punch-Through) device but is equipped with a shortcircuiting withstanding capability more than two times higher than that of the same. The insulated-type IGBT module is now drawing attention in place of the conventional GTO thyristor as a DC power supply constituting element for use in subway trains and others in and in the suburbs of big cities since it is easier to handle, maintain, and drive, and is capable of rapider switching. Hence, the development of the IGBT for use in 2-level inverters to deal with overhead line voltages of 750VAC and 1500VAC. Another technology described in this report relates to packaging that provides a long-term reliability for inverters in operation aboard vehicles. 3 refs., 14 figs., 3 tabs.

Miyashita, S.; Takubo, H.; Yoshiwatari, S. [Fuji Electric Co. Ltd., Tokyo (Japan)

1997-04-10

430

Stable Optical Phase Modulation with Micromirrors  

CERN Multimedia

We measure the motional fluctuations of a micromechanical mirror using a Michelson interferometer, and demonstrate its interferometric stability. The position stability of the micromirror is dominated by the thermal mechanical noise of the structure. With this level of stability, we utilize the micromirror to realize an ideal optical phase modulator by simply reflecting light off the mirror and modulating its position. The resonant frequency of the modulator can be tuned by applying a voltage between the mirror and an underlying electrode. Full modulation depth of +/-\\pi is achieved when the mirror resonantly excited with a sinusoidal voltage at an amplitude of 11V.

Knoernschild, Caleb; Maunz, Peter; Crain, Stephen; Kim, Jungsang

2011-01-01