WorldWideScience
 
 
1

Residual amplitude modulation in interferometric gravitational wave detectors.  

Science.gov (United States)

The effects of residual amplitude modulation (RAM) in laser interferometers using heterodyne sensing can be substantial and difficult to mitigate. In this work, we analyze the effects of RAM on a complex laser interferometer used for gravitational wave detection. The RAM introduces unwanted offsets in the cavity length signals and thereby shifts the operating point of the optical cavities from the nominal point via feedback control. This shift causes variations in the sensing matrix, and leads to degradation in the performance of the precision noise subtraction scheme of the multiple-degree-of-freedom control system. In addition, such detuned optical cavities produce an optomechanical spring, which also perturbs the sensing matrix. We use our simulations to derive requirements on RAM for the Advanced LIGO (aLIGO) detectors, and show that the RAM expected in aLIGO will not limit its sensitivity. PMID:24561943

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

2014-01-01

2

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

3

Residual amplitude modulation mechanisms in modulation transfer spectroscopy that use electro-optic modulators  

International Nuclear Information System (INIS)

Three independent mechanisms are described that contaminate the phase-modulated pump beam of an optical frequency reference stabilized by modulation transfer spectroscopy (MTS) with residual amplitude modulation (RAM). The electro-optic modulator, the beam geometry and the absorption of the saturated medium all separately generate undesired RAM that degrades the accuracy of the optical frequency reference. An analysis is presented that shows how frequency shifts introduced by the different mechanisms can be evaluated in typical MTS set-ups and minimized. The analysis also shows how the detector phase can be used to measure the total RAM in the system and how the phase required to remove any remaining frequency offsets can be evaluated

2009-02-01

4

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

Science.gov (United States)

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

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

2014-04-01

5

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

Science.gov (United States)

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

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

2009-06-01

6

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

7

Optical residue processing module  

Science.gov (United States)

An experimental program was conducted which demonstrated the Source Modulator Outer Product (SMOP) concept for high speed, high efficiency residue number system (RNS) computation. The optical architecture includes the outer product portion and a mapping portion to implement a Lookup Table (LUT). A Fourier transform based approach proved better suited to this architecture than did an image-based approach. Also, while the mapping was experimentally performed with optical fibers, a free-space approach based on an array of holographic optical elements is also contemplated. The end product of this research effort included experimental demonstration and a preliminary design of a high performance optical RNS processor based on the SMOP approach.

Haney, Michael W.; Levy, James J.; Athale, Ravindra A.; Euliss, Gary W.

1993-05-01

8

Speech production in amplitude-modulated noise.  

DEFF Research Database (Denmark)

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

Macdonald, Ewen N

2013-01-01

9

Amplitude modulation of wind turbine noise  

CERN Multimedia

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

10

Amplitude and phase modulation with waveguide optics  

International Nuclear Information System (INIS)

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

1996-10-22

11

Speech recognition with amplitude and frequency modulations  

Science.gov (United States)

Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance.

Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli

2005-01-01

12

[Amplitude modulation following responses in audiological diagnostics].  

Science.gov (United States)

The registration of brainstem potentials currently represents one of the most common methods in objective audiological diagnostics. However, regardless of their use, they are still known to possess important disadvantages, such as low specificity and validity in the lower frequency range due to broadband stimuli, or uncertainties due to the need for subjective evaluation. One potential solution to these problems could involve the registration of amplitude modulation following responses (AMFR). These potentials are being discussed much more regularly within the anglo-american literature due to their known frequency specificity within the high frequency range (resulting from a very narrow frequency band of stimulation), and also their ability to permit assessment of the hearing threshold at lower frequencies. Another additional advantage of AMFR results from the simple statistical verification of its presence.Extensive studies on the influence of both stimulating and recording parameters have also shown that the registration of AMFR could prove to be a very promising audiological tool, with past interest being focussed primarily on the optimal modulation frequency, the influence of vigilance of the generation of potentials, and the precise assessment of an objective threshold. PMID:12474125

Pethe, J; Mühler, R; von Specht, H

2002-12-01

13

Spatial amplitude and phase modulation using commercial twisted nematic LCDs  

CERN Document Server

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

van Putten, E G; Mosk, A P

2007-01-01

14

Amplitude-modulation detection by gerbils in reverberant sound fields.  

Science.gov (United States)

Reverberation can dramatically reduce the depth of amplitude modulations which are critical for speech intelligibility. Psychophysical experiments indicate that humans' sensitivity to amplitude modulation in reverberation is better than predicted from the acoustic modulation depth at the receiver position. Electrophysiological studies on reverberation in rabbits highlight the contribution of neurons sensitive to interaural correlation. Here, we use a prepulse-inhibition paradigm to quantify the gerbils' amplitude modulation threshold in both anechoic and reverberant virtual environments. Data show that prepulse inhibition provides a reliable method for determining the gerbils' AM sensitivity. However, we find no evidence for perceptual restoration of amplitude modulation in reverberation. Instead, the deterioration of AM sensitivity in reverberant conditions can be quantitatively explained by the reduced modulation depth at the receiver position. We suggest that the lack of perceptual restoration is related to physical properties of the gerbil's ear input signals and inner-ear processing as opposed to shortcomings of their binaural neural processing. PMID:23603513

Lingner, Andrea; Kugler, Kathrin; Grothe, Benedikt; Wiegrebe, Lutz

2013-08-01

15

Frequency regulation of amplitude-modulated reflex klystron  

Energy Technology Data Exchange (ETDEWEB)

Modulation methods, which increase the signal-to-noise ratio, are widely used in microwave spectroscopy of gases and liquids. Narrow resonance lines cannot always be recorded, due to klystron frequency instability. A circuit is described that provides 100% amplitude modulation and frequency control of a klystron. The modulation frequency is 100 KHz. Automatic frequency control is provided by an external cavity.

Belov, A.A.

1986-06-01

16

Log-Likelihood Classification Of Quadrature Amplitude Modulation  

Directory of Open Access Journals (Sweden)

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

Savita Kamboj

2013-10-01

17

Mechanisms of amplitude modulation in wind turbine noise  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The noise produced by wind turbines is inherently time varying. This amplitude modulation is normally due to the directivity of the dominant trailing edge noise sources combined with the changing position and orientation of the rotating blades. In some circumstances the level and character of the amplitude modulation is altered and this paper outlines results from a Renewable UK funded research programme into the possible causes. Besides the variability of the normal trailing edge noise mecha...

Smith, Malcom; Bullmore, Andrew; Cand, Matthew; Davis, Robert

2012-01-01

18

Quantum model for electro-optical amplitude modulation.  

Science.gov (United States)

We present a quantum model for electro-optic amplitude modulation, which is built upon quantum models of the main photonic components that constitute the modulator, that is, the guided-wave beamsplitter and the electro-optic phase modulator and accounts for all the different available modulator structures. General models are developed both for single and dual drive configurations and specific results are obtained for the most common configurations currently employed. Finally, the operation with two-photon input for the control of phase-modulated photons and the important topic of multicarrier modulation are also addressed. PMID:21164859

Capmany, José; Fernández-Pousa, Carlos R

2010-11-22

19

Quantum model for electro-optical amplitude modulation  

CERN Document Server

We present a quantum model for electro-optic amplitude modulation, which is built upon quantum models of the main photonic components that constitute the modulator, that is, the guided-wave beamsplitter and the electro-optic phase modulator and accounts for all the different available modulator structures. General models are developed both for single and dual drive configurations and specific results are obtained for the most common configurations currently employed. Finally, the operation with two-photon input for the control of phase-modulated photons and the important topic of multicarrier modulation are also addressed.

Capmany, Jose; 10.1364/OE.18.025127

2011-01-01

20

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

2013-06-01

 
 
 
 
21

Modulated Amplitude Waves in Collisionally Inhomogeneous Bose-Einstein Condensates  

CERN Document Server

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

22

Superposed pulse amplitude modulation for visible light communication.  

Science.gov (United States)

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

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

2013-12-16

23

AMPLITUDE AND PHASE MODULATION FOR ULTRASONIC WIRELESS COMMUNICATION  

Directory of Open Access Journals (Sweden)

Full Text Available Short range wireless communications have been used more and more frequently in our life. But the electromagnetic fields waves also have some disadvantages. One of these disadvantages is health problems. Many studies shows the electromagnetic field waves using for communication may damage our health. And in most hospitals, they also have bans on the use of mobile phones and wide area networks because of Electromagnetic Interference. So this paper studied the use of ultrasound for wireless communication in air, instead of using electromagnetic field wave. In order to find an advisable modulation method for ultrasound wireless communication, Amplitude modulation method and Phased modulation method has been test.

Nan Gao

2014-04-01

24

Amplitude modulated drift wave packets in a nonuniform magnetoplasma  

CERN Document Server

We consider the amplitude modulation of low-frequency, long wavelength electrostatic drift wave packets in a nonuniform magnetoplasma with the effects of equilibrium density, electron temperature and magnetic field inhomogeneities. The dynamics of the modulated drift wave packet is governed by a nonlinear Schr\\"odinger equation. The latter is used to study the modulational instability of a Stoke's wave train to a small longitudinal perturbation. It is shown that the drift wave packet is stable (unstable) against the modulation when the drift wave number lies in $0< k < 1/\\sqrt{2}$ $(1/\\sqrt{2}modulated drift wave packet can propagate in the form of bright and dark envelope solitons or as a drift wave rogon.

Shukla, P K; 10.1016/j.physleta.2012.07.008

2012-01-01

25

Focusing Light through Random Photonic Media by Binary Amplitude Modulation  

CERN Document Server

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

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

2011-01-01

26

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

27

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

Science.gov (United States)

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

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

2013-12-01

28

Critical coupling control of a microresonator by laser amplitude modulation.  

Science.gov (United States)

We present a laser amplitude modulation technique to actively stabilize the critical coupling of a microresonator by controlling the evanescent coupling gap from an optical fiber taper. It is a form of nulled lock-in detection, which decouples laser intensity fluctuations from the critical coupling measurement. We achieved a stabilization bandwidth of ? 20 Hz, with up to 5 orders of magnitude displacement noise suppression at 10 mHz, and an inferred gap stability of better than a picometer/?Hz. PMID:22714249

Chow, Jong H; Taylor, Michael A; Lam, Timothy T-Y; Knittel, Joachim; Sawtell-Rickson, Jye D; Shaddock, Daniel A; Gray, Malcolm B; McClelland, David E; Bowen, Warwick P

2012-05-21

29

Longitudinal tracking with phase and amplitude modulated rf  

Energy Technology Data Exchange (ETDEWEB)

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.

Caussyn, D.D.; Ball, M.; Brabson, B. [Indiana Univ., Bloomington, IN (United States)] [and others

1993-06-01

30

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

1993-05-17

31

Performance of OFDM System with Constant Amplitude Modulation  

Directory of Open Access Journals (Sweden)

Full Text Available The Orthogonal Frequency Division Multiplexing (OFDM technique has recently received considerable attention for wireless networks. Despite its advantages, it has a major drawback of its high Peak-to-Average Power Ratio (PAPR value which affects the system efficiency and the cost. In this paper, a proposed system is discussed to achieve 0 dB PAPR value. It depends on a proposed block, called Constant Amplitude (CA modulation. The whole characteristic mathematical analysis is presented for the proposed system. Additionally, the complexity evolution is explained. Afterwards, many MATLAB simulation programs are executed. Time and frequency domain behaviors are presented. Furthermore, in-band distortion introduced by the proposed CA modulation is calculated in terms of Error Vector Magnitude (EVM. Moreover, the proposed system outperforms the conventional one when compared in terms of PAPR, equalization, and BER under Additive White Gaussian Noise (AWGN channel and multipath fading channels. In addition, the impact of the proposed scheme design parameter is studied.

Waleed Saad

2013-08-01

32

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

CERN Multimedia

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

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

2003-01-01

33

Inhomogeneous phase-visibility modulating interferometry by space on-off non-quadrature amplitude modulation.  

Science.gov (United States)

A new method in interferometry based on on-off non-quadrature amplitude modulation for object phase retrieval is presented. Although the technique introduces inhomogeneous visibility and phase variations in the interferogram, it is shown that the phase retrieval of a given object is still possible. This method is implemented by using three beams and two Mach-Zehnder interferometers in series. One of the arms of the system is used as a probe beam and the other two are used as reference beams, yielding from their sum the conventional reference beam of a two-beam interferometer. We demonstrate that, if there is a phase difference within the range of (0,?) between these two beams, the effect of modulation in both amplitude and phase is generated for the case of on-off non-quadrature amplitude modulation. An analytical discussion is provided to sustain this method. Numerical and experimental results are also shown. PMID:23938612

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

2013-07-29

34

Frequency discriminator with amplitude modulation for magnetic measurements  

International Nuclear Information System (INIS)

A device for measuring the Curie temperature and a value of spontaneous magnetization of ferromagnetic semiconductors and small anisotropy dielectrics is described. In the process of the measurements recorded are dependences on magnetic field and temperature of a real part of radiofrequent magnetic permeability of a specimen having a known value of demagnetizing factor. Device operation is based on linear conversion of LC circuit resonance frequency deviations caused with magnetization or temperature variation of the specimen under investigation serving as a core of inductance coil to voltage. Conversion is performed by means of a frequency detector using semiconductor tetrode. To improve sensitivity, amplitude modulation of high-frequency reference signal with subsequent synchronous detection is applied. The system provides 0.5 V/% conversion transconductance at a noise level <=2 mV and driff of zero level <=3 mV/h

1981-01-01

35

On the frequency spectrum of Amplitude Modulation Following Responses.  

Science.gov (United States)

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

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

2000-01-01

36

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

Science.gov (United States)

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

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

2014-04-01

37

Decadal amplitude modulation of two types of ENSO and its relationship with the mean state  

Energy Technology Data Exchange (ETDEWEB)

In this study, we classified two types of El Nino-Southern Oscillation (ENSO) events within the decadal ENSO amplitude modulation cycle using a long-term coupled general circulation model simulation. We defined two climate states - strong and weak ENSO amplitude periods - and separated the characteristics of ENSO that occurred in both periods. There are two major features in the characteristics of ENSO: the first is the asymmetric spatial structure between El Nino and La Nina events; the second is that the El Nino-La Nina asymmetry is reversed during strong and weak ENSO amplitude periods. El Nino events during strong (weak) ENSO amplitude periods resemble the Eastern Pacific (Central Pacific) El Nino in terms of the spatial distribution of sea surface temperature anomalies (SSTA) and physical characteristics based on heat budget analysis. The spatial pattern of the thermocline depth anomaly for strong (weak) El Nino is identical to that for weak (strong) La Nina, but for an opposite sign and slightly different amplitude. The accumulated residuals of these asymmetric anomalies dominated by an east-west contrast structure could feed into the tropical Pacific mean state. Moreover, the residual pattern associated with El Nino-La Nina asymmetry resembles the first principal component analysis (PCA) mode of tropical Pacific decadal variability, indicating that the accumulated residuals could generate the change in climate state. Thus, the intensified ENSO amplitude yields the warm residuals due to strong El Nino and weak La Nina over the eastern tropical Pacific. This linear relationship between ENSO and the mean state is strong during the mature phases of decadal oscillation, but it is weak during the transition phases. Furthermore, the second PCA mode of tropical Pacific decadal variability plays an important role in changing the phase of the first mode. Consequently, the feedback between ENSO and the mean state is positive feedback to amplify the first PCA mode, whereas the second PCA mode is a negative feedback to lead the phase change of the first PCA mode due to their lead-lag relationship. These features could be regarded as evidence that the decadal change in properties of ENSO could be generated by the nonlinear interaction between ENSO and the mean state on a decadal-to-interdecadal time scale. (orig.)

Choi, Jung; An, Soon-Il [Yonsei University, Department of Atmospheric Sciences, Global Environmental Laboratory, Seoul (Korea, Republic of); Yeh, Sang-Wook [Hanyang University, Department of Environmental Marine Science, Ansan (Korea, Republic of)

2012-06-15

38

Some key issues on the optimization of multiple quantum well structures for amplitude modulation  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Main parameters of InGaAs/InAlAs multiple quantum well amplitude modulators, such as contrast ratio, insertion loss and chirp parameter, were calculated in order to find a quantum well structure which optimizes them. The parameters were estimated from the theoretical absorption curves, which were ca [...] lculated for different values of applied reverse bias and were compared with experimental data. A study of the device parameters as a function of the Ga content and operation voltage was performed. The study showed that optimum values for the modulator parameters cannot be obtained simultaneously. The influence of the residual doping level and the applied pre-bias are emphasized.

C.V-B., Tribuzy; M. P., Pires; B., Yavich; P. L., Souza.

39

Modifications and lithography on iridovirus surface using amplitude modulated nanolithography  

Science.gov (United States)

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

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

2004-04-01

40

nipi delta-doping superlattices for amplitude modulation  

Scientific Electronic Library Online (English)

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

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

 
 
 
 
41

Conversion of phase-modulated signals to amplitude-modulated signals in SOAs due to mirror reflections  

DEFF Research Database (Denmark)

We present theoretical results that show conversion of phase modulated signals to amplitude modulated signals in an SOA. Large-signal and small-signal calculations show significant conversion responses caused by even minute reflections at the end mirrors.

Blaaberg, Søren; Mørk, Jesper

2009-01-01

42

Constant RMS versus constant peak modulation for the perceptual equivalence of sinusoidal amplitude modulated signals.  

Science.gov (United States)

Neuroprosthetics using intracortical microstimulation can potentially alleviate sensory deprivation due to injury or disease. However the information bandwidth of a single microstimulation channel remains largely unanswered. This paper presents three experiments that examine the importance of Peak Power/Charge and RMS Power/Charge for detection of acoustic and electrical Sinusoidal Amplitude Modulated stimuli by the auditory system. While the peripheral auditory system is sensitive to RMS power cues for the detection of acoustic stimuli, here we provide results that suggest that the auditory cortex is sensitive to peak charge cues for electrical stimuli. Varying the modulation frequency and depth do not change this effect for detection of modulated electrical stimuli. PMID:24110387

Regele, Oliver B; Koivuniemi, Andrew S; Otto, Kevin J

2013-01-01

43

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Middlebrooks, John C.

2008-01-01

44

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

45

Effects of stimulus duration on amplitude modulation processing with cochlear implants  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study investigated temporal integration processes underlying cochlear implant (CI) users’ amplitude modulation processing. Thresholds for modulation detection (AMDTs) and modulation frequency discrimination (AMFDTs) were measured for 50-, 100-, and 200-Hz modulation frequencies with stimulus durations from 50 to 400 ms in eight adult CI users. The results showed significant interactions between modulation frequency and stimulus duration for AMDTs and AMFDTs. The data suggest that tempo...

2010-01-01

46

Trellis-coded pulse amplitude modulation for indoor visible light communication  

Science.gov (United States)

Trellis-coded pulse-amplitude modulation (TC-PAM) is applied in visible light communication (VLC) system using RGB-LED. Based on natural modulation, we propose a modified modulation to yield performance enhancement. Further, a decoding method of combing soft-decision Viterbi algorithm with most significant bit (MSB) decoding is developed. Finally, the results of Monte-Carlo simulation are presented to verify the best modulation and decoding method among the mentioned modulation and decoding techniques.

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

2013-12-01

47

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

DEFF Research Database (Denmark)

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

Hoffmann, Pablo F.

2010-01-01

48

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

49

Constant Amplitude and Triangular Modulation Cumulative Fatigue Damage Tests on Notched Steel Specimens.  

Science.gov (United States)

The interaction effects between high and low load levels were investigated to gain information on the qualitative and quantitative effects of axial loading conditions. Test results are tabulated for constant amplitude, axial loading; triangular modulation...

D. J. Ashby D. H. Baker

1975-01-01

50

Lateralization based on interaural differences in the second-order amplitude modulator.  

Science.gov (United States)

Second-order amplitude modulation is a relatively slow variation of the modulation depth of a first-order amplitude modulation with higher frequency. In contrast to first-order modulation, which appears as a physical component in the stimulus spectrum after half-wave rectification, second-order modulation is not necessarily demodulated by the auditory periphery. For binaural processing of second-order amplitude modulated stimuli it is unknown whether interaural time differences (ITDs) in the second-order modulation result in a lateralized percept. Thus, second-order modulation can serve as a tool to investigate whether demodulation of interaurally delayed components is a prerequisite for lateralization. In most of the psychoacoustic experiments presented here, a 25 Hz sinusoidally amplitude-modulated (SAM) 160 Hz tone was either transposed to 4 kHz by half-wave rectifying this SAM waveform before multiplication with a 4 kHz tone (TSAM), or by adding an offset before multiplication (SAMAM). The experiments revealed an inability to lateralize the SAMAM based on ITDs in the 25 Hz component, whereas subjects could lateralize the TSAM. Given that only the TSAM results in a demodulated 25 Hz component after peripheral auditory processing, this result supports the hypothesis that demodulation is a prerequisite for lateralization, which has consequences for temporal modulation processing in models of binaural interaction. PMID:22280601

Dietz, Mathias; Ewert, Stephan D; Hohmann, Volker

2012-01-01

51

Amplitude modulation following responses in awake and sleeping humans--a comparison for 40 Hz and 80 Hz modulation frequency.  

Science.gov (United States)

There have been several studies, which suggest that the amplitude of amplitude modulation following responses (AMFR) is correlated to the state of vigilance, similar to the 40 Hz event-related potentials. The aim of the present study was to compare the dependency of the AMFR-amplitude from the state of sleep for 40 Hz and 80 Hz modulation frequency. Eight normal hearing adults were investigated during natural and drug-induced sleep. The stimuli used were sinusoidally amplitude-modulated tones of 1 kHz carried frequency and 40 or 80 Hz modulation frequency at 60 dB nH stimulation level. For 40 Hz modulation frequency an increase of EEG-activity in the Delta-and Theta-band during periods of sleep correlates significantly with a decreased AMFR-amplitude whereas for 80 Hz no significant relation between stage of sleep and AMFR-amplitude could be found. The results suggest that in audiological use of 40 Hz-AMFR the state of vigilance should be monitored and stabilized at a high level. PMID:11318452

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

2001-01-01

52

EFFECTS OF CONTINUOUS-WAVE, PULSED, AND SINUSOIDAL-AMPLITUDE-MODULATED MICROWAVES ON BRAIN ENERGY METABOLISM  

Science.gov (United States)

A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...

53

One-shot phase-visibility modulating interferometry by on–off non-quadrature amplitude modulation  

Science.gov (United States)

This manuscript presents a proposal for achieving in a single-shot the phase-visibility modulating interferometry method. The setup is based on a 4f optical system consisting of three apertures at the input plane and a grid with a fill factor of 1/2 at the Fourier plane. One of the apertures serves as a probe beam and the other two apertures serve as reference beams, with which a reference beam modulated in phase and amplitude by the on–off non-quadrature amplitude modulation method is created. We show that the grid implements simultaneously the on–off non-quadrature amplitude modulation technique; therefore multiple interferograms can be obtained in a single-shot. A theoretical model will be shown supported by the experimental results.

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

2014-07-01

54

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-06-15

55

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

Science.gov (United States)

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

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

2014-06-01

56

Smooth Pursuit Saccade Amplitude Modulation During Exposure to Microgravity  

Science.gov (United States)

Russian investigators have reported changes in pursuit tracking of a vertically moving point stimulus during space flight. Early in microgravity, changes were manifested by decreased eye movement amplitude (undershooting) and the appearance of correction saccades. As the flight progressed, pursuit of the moving point stimulus deteriorated while associated saccadic movements were unchanged. Immediately postflight there was an improved execution of active head movements indicating that the deficiencies in pursuit function noted in microgravity may be of central origin. In contrast, tests of two cosmonauts showed that horizontal and vertical smooth pursuit were unchanged inflight. However, results of corresponding saccadic tasks showed a tendency toward the overshooting of a horizontal target early inflight with high accuracy developing later inflight, accompanied by an increased saccade velocity and a trend toward decreased saccade latency. Based on these equivocal results, we have further investigated the effects of space flight on the smooth pursuit mechanism during and after short duration flight, and postflight on returning MIR crewmembers. Sinusoidal target movement was presented horizontally at frequencies of 0.33 and 1.0 Hz. Subjects were asked to perform two trials for each stimulus combination: (1) moving eyes-only (EO) and (2) moving eyes and head (EH) with the target motion. Peak amplitude was 30 deg for 0.33 Hz trials and 15 deg for the 1.0 Hz trials. The relationship between saccade amplitude and peak velocity were plotted as a main sequence for each phase of flight, and linear regression analysis allowed us to determine the slope of each main sequence plot. The linear slopes were then combined for each flight phase for each individual subject. The main sequence for both EO and EH trials at both the 0.33 and 1.0 Hz frequencies during flight for the short duration flyers showed a reduction in saccade velocity and amplitude when compared to the preflight main sequence . This difference in the regression slopes between flight phase, head/eye condition (EO or EH), and pursuit target frequency was observed across all subjects (statistically significant at the p<0.02, df= 2). It is interesting to note that postflight for the short duration flyers there was an immediate recovery to the preflight main sequence across all trials. There were no significant differences observed between the preflight slopes for either head movement condition (EO vs. EH). When the immediate postflight (R+O) regression slopes were compared with the preflight slopes, there was a tendency (not significant) for both saccade amplitude and peak velocity to increase during the postflight testing. This tendency had vanished by R+ 1. Of particular interest was the redistribution of saccades during the latter stages of the flight and immediately postflight in the EO condition. At the 1.0 Hz frequency the saccades tended to be clustered near the lowest target velocity. It was also interesting to note that gaze performance (eye in skull + head in space) was consistently better during the EH condition; a finding also observed by our Russian colleagues. As the results of the long duration flight become available we expect that they will not only show that postflight effects will be similar to those observed during the short duration flights, but will also last for a greater period of time following flight. It is not clear what mechanism is responsible for the decreased peak saccadic velocity during flight unless the change is related to the control of retinal slip. For example, it is possible that saccades will tend to initially undershoot their targets by a small percentage and these saccades are then followed, if vision is available, by a small augmenting corrective saccade. It has been postulated that the functional significance of this undershooting tendency is to maintain the spatial representation of the target on the same side of the fovea (as opposedo racing across the fovea) and hence in the same cerebral hemisphere that initiated the primar

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

2002-01-01

57

Radio frequency path characterization for wide band quadrature amplitude modulation  

Energy Technology Data Exchange (ETDEWEB)

Remote, high speed, high explosive wave front monitoring requires very high bandwidth telemetry to allow transmission of diagnostic data before the explosion destroys the sensor system itself. The main motivation for this study is that no known existing implementation of this sort has been applied to realistic weapons environments. These facts have prompted the research and gathering of data that can be used to extrapolate towards finding the best modulation method for this application. In addition to research of similar existing analysis and testing operations, data was recently captured from a Joint Test Assembly (JTA) Air Launched Cruise Missile (ALCM) flight.

Bracht, R.

1998-12-31

58

Effect of large-amplitude alternating current modulation on apparent reversibility of electrode processes.  

Science.gov (United States)

We examined the effect of a large-amplitude high-frequency alternating potential modulation on direct currents associated with irreversible, quasi-reversible, and reversible electron-transfer processes occurring at microelectrodes under voltammetric conditions. All irreversible processes appear to be accelerated by the superimposed ac modulation, and under certain conditions this may even lead to an electrochemical etching of noble metal electrodes. In the case of electrode processes which are reversible on the time scale of a dc polarization, but quasi-reversible on the time scale of the ac modulation, the distortion of voltammograms caused by the ac modulation can provide useful information about the kinetics of fast electron-transfer processes. For completely reversible electrode processes the effect of the large-amplitude ac modulation is essentially trivial; the distortion of voltammetric curves causes broadening of analytical signals without providing any useful information. PMID:20825176

Baranski, Andrzej S; Boika, Aliaksei

2010-10-01

59

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

60

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

Science.gov (United States)

Detection and modulation rate discrimination were measured in cochlear-implant users for pulse-trains that were either sinusoidally amplitude modulated or were modulated with half-wave rectified sinusoids, which in acoustic hearing have been used to simulate the response to low-frequency temporal fine structure. In contrast to comparable results from acoustic hearing, modulation rate discrimination was not statistically different for the two stimulus types. The results suggest that, in contrast to binaural perception, pitch perception in cochlear-implant users does not benefit from using stimuli designed to more closely simulate the cochlear response to low-frequency pure tones. PMID:20136187

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

2010-02-01

 
 
 
 
61

Amplitude modulation of sound from wind turbines under various meteorological conditions.  

Science.gov (United States)

Wind turbine (WT) sound annoys some people even though the sound levels are relatively low. This could be because of the amplitude modulated "swishing" characteristic of the turbine sound, which is not taken into account by standard procedures for measuring average sound levels. Studies of sound immission from WTs were conducted continually between 19 August 2011 and 19 August 2012 at two sites in Sweden. A method for quantifying the degree and strength of amplitude modulation (AM) is introduced here. The method reveals that AM at the immission points occur under specific meteorological conditions. For WT sound immission, the wind direction and sound speed gradient are crucial for the occurrence of AM. Interference between two or more WTs could probably enhance AM. The mechanisms by which WT sound is amplitude modulated are not fully understood. PMID:24437746

Larsson, Conny; Öhlund, Olof

2014-01-01

62

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

2013-01-01

63

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

Science.gov (United States)

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.

Ow, Y. S.; Breese, M. B. H.; Leng, Y. R.; Azimi, S.; Teo, E. J.; Sun, X. W.

2010-05-01

64

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

Science.gov (United States)

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

Parkkonen, Lauri; Hari, Riitta

2014-01-01

65

Near-threshold recordings of amplitude modulation following responses (AMFR) in children of different ages.  

Science.gov (United States)

Amplitude modulation following responses (AMFR) to single near-threshold 40-Hz or 80-Hz amplitude-modulated tones of 1 kHz were recorded in 48 normal children between the ages of 2 months and 14 years. Children under the age of 2 years were tested during natural sleep, and older children were tested awake. The objectives of this study were to find out how the AMFR changes with age and to determine the most effective modulation frequency for objective threshold assessment at different ages. The optimal modulation frequency changed from higher to lower modulation frequencies at about 13 years. In younger children, the 80-Hz AMFR was larger than the 40-Hz AMFR. The 40-Hz response became similar to the adult response by the age of 14 years, while the 80-Hz response had an amplitude greater than half of an adult response by the age of 1 year, changed very little during the investigated period, and reached the amplitude of adult responses at the end of the investigated period. PMID:15457816

Pethe, Joachim; Mühler, Roland; Siewert, Karen; von Specht, Hellmut

2004-06-01

66

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

Directory of Open Access Journals (Sweden)

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

Miriam Jaafar

2012-04-01

67

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

Science.gov (United States)

Summary 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.

Jaafar, Miriam; Cuenca, Mariano; Melcher, John; Raman, Arvind

2012-01-01

68

Synthesis of electro-optic modulators for amplitude modulation of light  

Science.gov (United States)

Electro-optical modulator realizes voltage transfer function in synthesizing birefringent networks. Choice of the voltage transfer function is important, the most satisfactory optimizes the modulator property.

Ammann, E. O.; Yarborough, J. M.

1968-01-01

69

Radar transponder operation with compensation for distortion due to amplitude modulation  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-01-04

70

Differential Space-Time Coding Scheme Using Star Quadrature Amplitude Modulation Method  

Directory of Open Access Journals (Sweden)

Full Text Available Differential space-time coding (DSTC has received much interest as it obviates the requirement of the channel state information at the receiver while maintaining the desired properties of space-time coding techniques. In this paper, by introducing star quadrature amplitude modulation (star QAM method, two kinds of multiple amplitudes DSTC schemes are proposed. One is based on differential unitary space-time coding (DUSTC scheme, and the other is based on differential orthogonal space-time coding (DOSTC scheme. Corresponding bit-error-rate (BER performance and coding-gain analysis are given, respectively. The proposed schemes can avoid the performance loss of conventional DSTC schemes based on phase-shift keying (PSK modulation in high spectrum efficiency via multiple amplitudes modulation. Compared with conventional PSK-based DSTC schemes, the developed schemes have higher spectrum efficiency via carrying information not only on phases but also on amplitudes, and have higher coding gain. Moreover, the first scheme can implement low-complexity differential modulation and different code rates and be applied to any number of transmit antennas; while the second scheme has simple decoder and high code rate in the case of 3 and 4 antennas. The simulation results show that our schemes have lower BER when compared with conventional DUSTC and DOSTC schemes.

Bi Guangguo

2006-01-01

71

Effect of amplitude modulation and phase perturbation on the optimizing parameters of third harmonic generation  

International Nuclear Information System (INIS)

Effect of amplitude modulation and phase perturbation of incident fundamental field on the tripling efficiency and dynamic range has been discussed in details. The method which can improve the tripling efficiency and dynamic range has been proposed. Using type I/II angle-detuning scheme for third harmonic generation, the parameter of harmonic conversion crystal has been optimized

2003-01-01

72

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

CERN Document Server

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

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

2009-01-01

73

Amplitude Modulation  

Science.gov (United States)

This tutorial is part of the National Instruments Measurement Fundamentals series. Each tutorial in this series teaches a specific topic of common measurement applications by explaining the theory and giving practical examples. This tutorial covers an introduction to RF, wireless, and high-frequency signals and systems. A PDF of the tutorial is available for download.

2013-08-13

74

Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator.  

Science.gov (United States)

We utilize various techniques to characterize the residual phase modulation of a waveguide-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement. PMID:20173940

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

2010-01-18

75

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

CERN Document Server

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

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

2009-01-01

76

Walking phase modulates H-reflex amplitude in flexor carpi radialis.  

Science.gov (United States)

It is well established that remote whole-limb rhythmic movement (e.g., cycling or stepping) induces suppression of the Hoffman (H-) reflex evoked in stationary limbs. However, the dependence of reflex amplitude on the phase of the movement cycle (i.e., phase-dependence) has not been consistent across this previous research. The authors investigated the phase-dependence of flexor carpi radialis (FCR) H-reflex amplitudes during active walking and in kinematically matched static postures across the gait cycle. FCR H-reflexes were elicited in the stationary forearm with electrical stimulation to the median nerve. Significant phase-dependent modulation occurred during walking when the gait cycle was examined with adequate phase resolution. The suppression was greatest during midstance and midswing, suggesting increased ascending communication during these phases. There was no phase-dependent modulation in static standing postures and no correlation between lower limb background electromyography levels and H-reflex amplitude during active walking. This evidence, along with previous research demonstrating no phase modulation during passive walking, suggests that afferent feedback associated with joint position and leg muscle activation levels are not the sole source of the phase modulation seen during active walking. Possible sources of phase modulation include combinations of afferent feedback related to active movement or central motor commands or both. PMID:24313749

Domingo, Antoinette; Klimstra, Marc; Nakajima, Tsuyoshi; Lam, Tania; Hundza, Sandra R

2014-01-01

77

NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS  

International Nuclear Information System (INIS)

Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times have not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts of acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.

2010-01-10

78

Perceptual learning and generalization resulting from training on an auditory amplitude-modulation detection taska  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fluctuations in sound amplitude provide important cues to the identity of many sounds including speech. Of interest here was whether the ability to detect these fluctuations can be improved with practice, and if so whether this learning generalizes to untrained cases. To address these issues, normal-hearing adults (n?=?9) were trained to detect sinusoidal amplitude modulation (SAM; 80-Hz rate, 3–4 kHz bandpass carrier) 720 trials?day for 6–7 days and were tested before and after tra...

Fitzgerald, Matthew B.; Wright, Beverly A.

2011-01-01

79

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

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

Ghaffar, Farhan A.

2012-09-30

80

The effect of weld residual stresses and their re-distribution with crack growth during fatigue under constant amplitude loading  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work the evolution of the residual stresses in a MIG-welded 2024-T3 aluminium alloy M(T) specimen during in situ fatigue crack growth at constant load amplitude has been measured with neutron diffraction. The plastic relaxation and plasticity-induced residual stresses associated with the fatigue loading were found to be small compared with the stresses arising due to elastic re-distribution of the initial residual stress field. The elastic re-distribution was modelled with a finite el...

Liljedahl, C. D. M.; Zanellato, O.; Fitzpatrick, M. E.; Lin, J.; Edwards, L.

2010-01-01

 
 
 
 
81

Amplitude, phase, and hybrid ternary modulation modes of a twisted-nematic liquid-crystal display at approximately 400 nm.  

Science.gov (United States)

Applicability of a commercial twisted-nematic liquid-crystal display is examined at approximately 400 nm. Different modulation modes predicted by Jones-matrix calculus are experimentally tested. High contrast amplitude modulation with negligible loss, high contrast and low loss hybrid ternary modulation, and 1.5pi continuous phase delay without intensity modulation and with low loss are presented. Simulation results of a 4f holographic system prove the usefulness of the high contrast for amplitude modulation, and the importance of pi phase difference between high transmission white levels in a hybrid ternary modulation. PMID:12816330

Reményi, Judit; Várhegyi, Péter; Domján, László; Koppa, Pál; Lõrincz, Emõke

2003-06-10

82

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

CERN Document Server

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

Goorden, Sebastianus A; Mosk, Allard P

2014-01-01

83

Quantitative security evaluation of optical encryption using hybrid phase- and amplitude-modulated keys.  

Science.gov (United States)

In the increasing number of system approaches published in the field of optical encryption, the security level of the system is evaluated by qualitative and empirical methods. To quantify the security of the optical system, we propose to use the equivalent of the key length routinely used in algorithmic encryption. We provide a calculation method of the number of independent keys and deduce the binary key length for optical data encryption. We then investigate and optimize the key length of the combined phase- and amplitude-modulated key encryption in the holographic storage environment, which is one of the promising solutions for the security enhancement of single- and double-random phase-encoding encryption and storage systems. We show that a substantial growth of the key length can be achieved by optimized phase and amplitude modulation compared to phase-only encryption. We also provide experimental confirmation of the model results. PMID:22358164

Sarkadi, Tamás; Koppa, Pál

2012-02-20

84

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

85

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

Science.gov (United States)

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

Trosin, Barry James

2007-01-01

86

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

CERN Multimedia

In recent years diode laser sources have become widespread and reliable tools in magneto-optical spectroscopy. In particular, laser-driven atomic magnetometers have found a wide range of practical applications. More recently, so-called magnetically silent variants of atomic magnetometers have been developed. While in conventional magnetometers the magnetic resonance transitions between atomic sublevels are phase-coherently driven by a weak oscillating magnetic field, silent magnetometers use schemes in which either the frequency (FM) or the amplitude (AM) of the light beam is modulated. Here we present a theoretical model that yields algebraic expressions for the parameters of the multiple resonances that occur when either amplitude-, frequency- or polarization-modulated light of circular polarization is used to drive the magnetic resonance transition in a transverse magnetic field. The relative magnitudes of the resonances that are observed in the transmitted light intensity at harmonic m of the Larmor frequ...

Gruji?, Z D

2013-01-01

87

Surface plasmon polariton induced optical amplitude and phase modulation in sub-wavelength apertures.  

Science.gov (United States)

We report on the amplitude and phase modulation of picosecond optical pulses, near ? = 800 nm, transmitted through sub-wavelength rectangular apertures in thin gold films with thicknesses of ?/10 at per-pulse energies of aperture. Due to the excitation and strong confinement of surface plasmon polaritons in the apertures, the leading edge of a pulse causes a rapid heating of the electrons and lattice to modulate its falling edge. By comparing cross-correlation frequency resolved optical gating measurements with simulations, the thermal effects responsible for the induced pulse dynamics are identified. PMID:21643088

Joushaghani, Arash; Hou, Bo; Aitchison, J Stewart; Poon, Joyce K S

2011-04-25

88

Specificity of Binaural Perceptual Learning for Amplitude Modulated Tones: A Comparison of two Training Methods  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The specificity of auditory perceptual learning has been taken as an indicator of the likely locus within the brain at which underlying neuronal changes occur. This study examined interaural level difference (ILD) discrimination learning with sinusoidally amplitude modulated (SAM) tones and whether training-induced threshold improvements generalize from one side of auditory space to the other and to an untrained carrier frequency. A novel, dual-staircase adaptive method was adopted that was d...

Kumpik, Daniel; Ting, Jeremy; Campbell, Robert A. A.; Schnupp, Jan W. H.; King, Andrew J.

2009-01-01

89

Modulation of amplitude and latency of motor evoked potential by direction of transcranial magnetic stimulation  

Science.gov (United States)

The present study analyzed the effects of monophasic magnetic stimulation to the motor cortex. The effects of magnetic stimulation were evaluated by analyzing the motor evoked potentials (MEPs). The amplitude and latency of MEPs on the abductor pollicis brevis muscle were used to evaluate the effects of repetitive magnetic stimulation. A figure eight-shaped flat coil was used to stimulate the region over the primary motor cortex. The intensity of magnetic stimulation was 120% of the resting motor threshold, and the frequency of magnetic stimulation was 0.1 Hz. In addition, the direction of the current in the brain was posterior-anterior (PA) or anterior-posterior (AP). The latency of MEP was compared with PA and AP on initial magnetic stimulation. The results demonstrated that a stimulus in the AP direction increased the latency of the MEP by approximately 2.5 ms. MEP amplitude was also compared with PA and AP during 60 magnetic stimulations. The results showed that a stimulus in the PA direction gradually increased the amplitude of the MEP. However, a stimulus in the AP direction did not modulate the MEP amplitude. The average MEP amplitude induced from every 10 magnetic pulses was normalized by the average amplitude of the first 10 stimuli. These results demonstrated that the normalized MEP amplitude increased up to approximately 150%. In terms of pyramidal neuron indirect waves (I waves), magnetic stimulation inducing current flowing backward to the anterior preferentially elicited an I1 wave, and current flowing forward to the posterior elicited an I3 wave. It has been reported that the latency of the I3 wave is approximately 2.5 ms longer than the I1 wave elicitation, so the resulting difference in latency may be caused by this phenomenon. It has also been reported that there is no alteration of MEP amplitude at a frequency of 0.1 Hz. However, this study suggested that the modulation of MEP amplitude depends on stimulation strength and stimulation direction.

Sato, Aya; Torii, Tetsuya; Iwahashi, Masakuni; Itoh, Yuji; Iramina, Keiji

2014-05-01

90

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

Science.gov (United States)

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

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

2012-04-01

91

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

Science.gov (United States)

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

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

2013-10-01

92

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

93

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

Energy Technology Data Exchange (ETDEWEB)

Calcium (/sup 45/Ca/sup 2 +/) 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 CaCl/sub 2/-stimulated /sup 45/Ca/sup 2 +/ 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.

Lin-Liu, S.; Adey, W.R.

1982-01-01

94

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

International Nuclear Information System (INIS)

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

2009-12-01

95

Limitations on accurate shape determination using amplitude modulation atomic force microscopy  

International Nuclear Information System (INIS)

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

2012-04-01

96

Hermitian $(a, b)$-modules and Saito's "higher residue pairings"  

CERN Document Server

Following the work of Daniel Barlet ([Bar97]) and Ridha Belgrade ([Bel01]) the aim of this article is the study of the existence of $(a, b)$-hermitian forms on regular $(a, b)$-modules. We show that every regular $(a,b)$-module with a non-degenerate bilinear form can be written in an unique way as a direct sum of $(a, b)$-modules $E_i$ that admit either an $(a, b)$-hermitian or an $(a, b)$-anti-hermitian form or both; all three cases are equally possible with explicit examples. As an application we extend the result in [Bel01] on the existence for all $(a, b)$-modules $E$ associated with the Brieskorn module of a holomorphic function with an isolated singularity, of an $(a,b)$-bilinear non degenerate form on $E$. We show that with a small transformation Belgrade's form can be considered $(a, b)$-hermitian and that the result satis es the axioms of Kyoji Saito's "higher residue pairings".

Karwasz, Piotr P

2011-01-01

97

Modulation of the phase and amplitude of RF pulse for the L-band electron linac at ISIR, Osaka University  

International Nuclear Information System (INIS)

We are conducting to develop free electron laser (FEL) in the terahertz region using the L-band electron linac. In order to generate a micro-bunched electron beam with uniform energy, the phase and amplitude of rf pulses were repeatedly controlled. Using a electrical phase shifter and an I-Q modulator for the low level rf pulse, we achieved the undulations of flat-top of the input rf pulse for the accelerating structure were reduced to 0.3deg (p-p) and 0.9% (p-p) in the phase and amplitude within 7.6 ?s pulse duration, respectively. Now, we are developing the rf pulse modulation system that uses the I-Q modulator only. Iterating modulation, we reduced the rf pulse modulation error to 0.4deg (p-p, phase) and 0.4% (p-p, amplitude) respectively at the low level test module. (author)

2008-08-06

98

Simulation of amplitude-modulated circularly polarized Alfven waves for beta less than one  

International Nuclear Information System (INIS)

We study the nonlinear properties of the amplitude-modulated circulary polarized Alfven wave for ?<1. The temporal behavior of the wave packet of the electromagnetic hybrid simulation is compared with a numerical solution of the derivative nonlinear Schroedinger (DNLS) equation. It is shown that the left-hand-polarized mode evolves into a shocklike structure due to the modulational instability. However, both cyclotron damping and a snowplow effect near the steepened wave packet suppress its further steepening, contrary to the predictions of the DNLS equation. For the right-hand mode, formation of the shock does not take place, and the initial time development is well described by the DNLS equation. The daughter Alfven wave and ion acoustic waves are excited due to the decay instability at a later time. Heating or acceleration of the particles takes place for both left- and right-hand waves. Energy transfer from the wave to the particles occurs effectively when substantial modulation in the wave amplitude is present. The significance of this result is briefly discussed. copyright American Geophysical Union 1987

1987-07-01

99

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

Energy Technology Data Exchange (ETDEWEB)

In ambient conditions, nanometric water layers form on hydrophilic surfaces covering them and significantly changing their properties and characteristics. Here we report the excitation of subharmonics in amplitude modulation atomic force microscopy induced by intermittent water contacts. Our simulations show that there are several regimes of operation depending on whether there is perturbation of water layers. Single period orbitals, where subharmonics are never induced, follow only when the tip is either in permanent contact with the water layers or in pure noncontact where the water layers are never perturbed. When the water layers are perturbed subharmonic excitation increases with decreasing oscillation amplitude. We derive an analytical expression which establishes whether water perturbations compromise harmonic motion and show that the predictions are in agreement with numerical simulations. Empirical validation of our interpretation is provided by the observation of a range of values for apparent height of water layers when subharmonic excitation is predicted.

Santos, Sergio [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Barcons, Victor [Departament de Disseny i Programacio de Sistemes Electronics, UPC - Universitat Politecnica de Catalunya Av. Bases, 61, 08242 Manresa (Spain); Verdaguer, Albert [Centre d' Investigacio en Nanociencia i Nanotecnologia (CIN2) (CSIC-ICN), Esfera UAB, Campus de la UAB, Edifici CM-7, 08193-Bellaterra, Catalunya (Spain); Chiesa, Matteo [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307 (United States)

2011-12-01

100

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

International Nuclear Information System (INIS)

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

2013-01-01

 
 
 
 
101

Neural Rate and Timing Cues for Detection and Discrimination of Amplitude-Modulated Tones in the Awake Rabbit Inferior Colliculus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Neural responses to amplitude-modulated (AM) tones in the unanesthetized rabbit inferior colliculus (IC) were studied in an effort to establish explicit relationships between physiological and psychophysical measures of temporal envelope processing. Specifically, responses to variations in modulation depth (m) at the cell’s best modulation frequency, with and without modulation maskers, were quantified in terms of average rate and synchronization to the envelope over the entire perceptual d...

Nelson, Paul C.; Carney, Laurel H.

2007-01-01

102

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

International Nuclear Information System (INIS)

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

2013-10-18

103

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2011-01-01

104

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.

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

2013-10-01

105

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

In order to solve the limitation of data rate caused by long rise and fall time of light emitting diodes, m-ary return-to-zero optical pulse amplitude modulation is proposed in this paper for improving the bandwidth efficiency of indoor visible light communication. M-ary return-to-zero optical pulse amplitude modulation transmits information through a subtle change of illumination intensity and supports both flicker mitigation and dimming control functions. An indoor communication link establ...

Guanghui Ren; Shengyang He; Yunlong Yang

2013-01-01

106

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

107

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

DEFF Research Database (Denmark)

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

Ghoreishy, Hoda; Varjani, Ali Yazdian

2013-01-01

108

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

Directory of Open Access Journals (Sweden)

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

AravindakshanParthasarathy

2010-12-01

109

Use of amplitude modulation cues recovered from frequency modulation for cochlear implant users when original speech cues are severely degraded.  

Science.gov (United States)

Won et al. (J Acoust Soc Am 132:1113-1119, 2012) reported that cochlear implant (CI) speech processors generate amplitude-modulation (AM) cues recovered from broadband speech frequency modulation (FM) and that CI users can use these cues for speech identification in quiet. The present study was designed to extend this finding for a wide range of listening conditions, where the original speech cues were severely degraded by manipulating either the acoustic signals or the speech processor. The manipulation of the acoustic signals included the presentation of background noise, simulation of reverberation, and amplitude compression. The manipulation of the speech processor included changing the input dynamic range and the number of channels. For each of these conditions, multiple levels of speech degradation were tested. Speech identification was measured for CI users and compared for stimuli having both AM and FM information (intact condition) or FM information only (FM condition). Each manipulation degraded speech identification performance for both intact and FM conditions. Performance for the intact and FM conditions became similar for stimuli having the most severe degradations. Identification performance generally overlapped for the intact and FM conditions. Moreover, identification performance for the FM condition was better than chance performance even at the maximum level of distortion. Finally, significant correlations were found between speech identification scores for the intact and FM conditions. Altogether, these results suggest that despite poor frequency selectivity, CI users can make efficient use of AM cues recovered from speech FM in difficult listening situations. PMID:24532186

Won, Jong Ho; Shim, Hyun Joon; Lorenzi, Christian; Rubinstein, Jay T

2014-06-01

110

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

CERN Document Server

A model of the CW high-power transmitter, utilizing frequency-locked magnetrons with a phase control studied initially as a prototype of controllable in phase and power an RF source for intensity-frontier superconducting linacs, was considered for telecommunication as a model of magnetron source, acceptable for a wideband phase-amplitude modulation at a precisely stable carrier frequency. The R&D conducted with CW, 2.45 GHz, 1 kW, microwave oven magnetrons demonstrated that the frequency locking of the magnetrons by the phase-modulated signal provides wideband phase and amplitude modulation at the modulating frequency at least up to 3 MHz and large magnitude, keeping the carrier frequency precisely stable, without broadening of the spectral line width. Performed experiments with power combining verified applicability of the transmitter based on the frequency-locked magnetrons for wideband phase and amplitude modulation, which may be used for telecommunication. Results of the experiments are described in t...

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

2014-01-01

111

Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links  

DEFF Research Database (Denmark)

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

Iglesias Olmedo, Miguel; Zuo, Tianjian

2014-01-01

112

Acute effects of levodopa on wrist movement in Parkinson's disease. Kinematics, volitional EMG modulation and reflex amplitude modulation.  

Science.gov (United States)

Acute changes in motor performance due to levodopa were evaluated by a series of four motor tests unified by their focus on wrist flexion-extension movements. Subjects with idiopathic Parkinson's disease were evaluated with this battery of tests before (OFF) and after their usual morning dose of levodopa (ON). The test battery consisted of (i) repetitive self-paced movement in which velocity was to be maximized; (ii) visually guided tracking of a sinusoid and a square wave; and (iii) an assay of stretch reflex modulation during volitional sinusoidal tracking. The maximal wrist joint velocity of self-paced reciprocating flexion and extension movements increased after levodopa (ON), without significant changes in the movement period or amplitude. In the two tracking tasks, some subjects improved as evident by a lower root mean square (rms) error, but in similar numbers of subjects the rms error increased. Overall, the rms error, peak velocity or peak movement amplitude did not change after levodopa in either tracking task. Significant and consistent changes did occur after levodopa in an assay of reflex modulation during error-constrained tracking (Johnson et al., Brain 1991; 114: 443-60). The amplitude of volitional EMG increased after levodopa, with a concurrent reduction in reflex EMG. These changes are consistent with the noted increase in movement velocity. These results show that the effects of levodopa on movement velocity were not consistently translated into increased accuracy. The changes in the long latency reflex gain argue for a central control of this reflex, mediated by structures sensitive to levodopa. Finally, the results show that the quantitative evaluation of levodopa therapy cannot be unidimensional, but requires a battery of motor tests as undertaken in this study. PMID:7820576

Johnson, M T; Mendez, A; Kipnis, A N; Silverstein, P; Zwiebel, F; Ebner, T J

1994-12-01

113

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

DEFF Research Database (Denmark)

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

Dau, Torsten

2008-01-01

114

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

115

Effect of modulation amplitude on low-field microwave absorption in hafnium-doped Y-Ba-Cu-O  

International Nuclear Information System (INIS)

Low-field differential microwave absorption has been studied for hafnium-doped Y-Ba-Cu-O at the first harmonic of modulation field. The effect of modulation amplitude on peak height, peak position and the area under hysteresis curve has been discussed. (author). 8 refs., 3 figs

1991-06-01

116

Auditory stream segregation on the basis of amplitude-modulation rate  

Science.gov (United States)

In this study, auditory stream segregation based on differences in the rate of envelope fluctuations-in the absence of spectral and temporal fine structure cues-was tested. The temporal sequences to segregate were composed of fully amplitude-modulated (AM) bursts of broadband noises A and B. All sequences were built by the reiteration of a ABA triplet where A modulation rate was fixed at 100 Hz and B modulation rate was variable. The first experiment was devoted to measuring the threshold difference in AM rate leading subjects to perceive the sequence as two streams as opposed to just one. The results of this first experiment revealed that subjects generally perceived the sequences as a single perceptual stream when the difference in AM rate between the A and B noises was smaller than 0.75 oct, and as two streams when the difference was larger than about 1.00 oct. These streaming thresholds were found to be substantially larger than, and not related to, the subjects' modulation-rate discrimination thresholds. The results of a second experiment demonstrated that AM-rate-based streaming was adversely affected by decreases in AM depth, but that segregation remained possible as long as the AM of either the A or B noises was above the subject's AM-detection threshold. The results of a third experiment indicated that AM-rate-based streaming effects were still observed when the modulations applied to the A and B noises were set individually, either at a constant level in dB above AM-detection threshold, or at levels at which they were of the same perceived strength. This finding suggests that AM-rate-based streaming is not necessarily mediated by perceived differences in AM depth. Altogether, the results of this study indicate that sequential sounds can be segregated on the sole basis of differences in the rate of their temporal fluctuations in the absence of other temporal or spectral cues.

Grimault, Nicolas; Bacon, Sid P.; Micheyl, Christophe

2002-03-01

117

Amplitude modulation and demodulation of an electromagnetic wave in magnetised acousto-optic diffusive semiconductor plasmas: Hot carrier effects  

Science.gov (United States)

In communication processes, amplitude modulation is very helpful to save power using a single band transmission. Using the hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave incorporating carrier heating (CH) effects in acousto-optic magnetised semiconductor plasma. The CH effects add new dimensions in the present analysis. Analysis are made under different wave number regions over a wide range of cyclotron frequencies. It is found that incorporation of CH effects modifies the amplitude modulation and demodulation processes effectively. Numerical estimations are made for III-V semiconductor crystal irradiated by pump wave of frequency 1.6×10 13 s -1. Complete absorption of the waves takes place in all the possible wavelength regimes when the cyclotron frequency ?c becomes nearly equal to ?0, the pump frequency on neglecting the collision term in modulation/ demodulation indices.

Nimje, Nilesh; Dubey, Swati; Ghosh, S.

2012-06-01

118

Optical-wireless-optical full link for polarization multiplexing quadrature amplitude/phase modulation signal transmission.  

Science.gov (United States)

We propose and experimentally demonstrate an optical wireless integration system at the Q-band, in which up to 40 Gb/s polarization multiplexing multilevel quadrature amplitude/phase modulation (PM-QAM) signal can be first transmitted over 20 km single-mode fiber-28 (SMF-28), then delivered over a 2 m 2 × 2 multiple-input multiple-output wireless link, and finally transmitted over another 20 km SMF-28. The PM-QAM modulated wireless millimeter-wave (mm-wave) signal at 40 GHz is generated based on the remote heterodyning technique, and demodulated by the radio-frequency transparent photonic technique based on homodyne coherent detection and baseband digital signal processing. The classic constant modulus algorithm equalization is used at the receiver to realize polarization demultiplexing of the PM-QAM signal. For the first time, to the best of our knowledge, we realize the conversion of the PM-QAM modulated wireless mm-wave signal to the optical signal as well as 20 km fiber transmission of the converted optical signal. PMID:24322113

Li, Xinying; Yu, Jianjun; Chi, Nan; Zhang, Junwen

2013-11-15

119

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

Science.gov (United States)

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

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

2013-01-01

120

Cochlear Gain Control Estimated from Distortion Product Otoacoustic Emissions Evoked by Amplitude Modulated Tones  

Science.gov (United States)

It is known that cochlear outer hair cells (OHCs) can provide dynamic feedback to the basilar membrane vibration. Nonlinearities in OHC activities can generate distortion product otoacoustic emissions (DPOAEs) measurable in the ear canal. If evoked by amplitude modulation (AM) signals, DPOAEs could provide a means to access the dynamic gain control of the cochlea. In this study, one of the primary stimuli was replaced with an AM tone to evoke DPOAEs in human ears. The results showed that the estimated cochlear gain decreased with the increase in stimulus level and the gain functions obtained from different AM tone levels were continuous. However, there was a difference in the gain functions depending on which primary was modulated. The gain showed a stronger compression when f2 was modulated. Considering that DPOAEs are mainly generated at the f2 place, it suggests that the cochlear gain control is more nonlinear for on-frequency signals. Using AM stimulus could provide clues on how dynamic signals are processed in the cochlea.

Chen, Shixiong; Bian, Lin

2011-11-01

 
 
 
 
121

Multiscale amplitude-modulation frequency-modulation (AM-FM) texture analysis of multiple sclerosis in brain MRI images.  

Science.gov (United States)

This study introduces the use of multiscale amplitude modulation-frequency modulation (AM-FM) texture analysis of multiple sclerosis (MS) using magnetic resonance (MR) images from brain. Clinically, there is interest in identifying potential associations between lesion texture and disease progression, and in relating texture features with relevant clinical indexes, such as the expanded disability status scale (EDSS). This longitudinal study explores the application of 2-D AM-FM analysis of brain white matter MS lesions to quantify and monitor disease load. To this end, MS lesions and normal-appearing white matter (NAWM) from MS patients, as well as normal white matter (NWM) from healthy volunteers, were segmented on transverse T2-weighted images obtained from serial brain MR imaging (MRI) scans (0 and 6-12 months). The instantaneous amplitude (IA), the magnitude of the instantaneous frequency (IF), and the IF angle were extracted from each segmented region at different scales. The findings suggest that AM-FM characteristics succeed in differentiating 1) between NWM and lesions; 2) between NAWM and lesions; and 3) between NWM and NAWM. A support vector machine (SVM) classifier succeeded in differentiating between patients that, two years after the initial MRI scan, acquired an EDSS ? 2 from those with EDSS > 2 (correct classification rate = 86%). The best classification results were obtained from including the combination of the low-scale IA and IF magnitude with the medium-scale IA. The AM-FM features provide complementary information to classical texture analysis features like the gray-scale median, contrast, and coarseness. The findings of this study provide evidence that AM-FM features may have a potential role as surrogate markers of lesion load in MS. PMID:21062681

Loizou, C P; Murray, V; Pattichis, M S; Seimenis, I; Pantziaris, M; Pattichis, C S

2011-01-01

122

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

2013-01-01

123

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

Science.gov (United States)

In this work we present a new AFM based approach to measure the local dielectric response of polymer films at the nanoscale by means of Amplitude Modulation Electrostatic Force Microscopy (AM-EFM). The proposed experimental method is based on the measurement of the tip-sample force via the detection of the second harmonic component of the photosensor signal by means of a lock-in amplifier. This approach allows reaching unprecedented broad frequency range (2-3 × 10(4)Hz) without restrictions on the sample environment. The method was tested on different poly(vinyl acetate) (PVAc) films at several temperatures. Simple analytical models for describing the electric tip-sample interaction semi-quantitatively account for the dependence of the measured local dielectric response on samples with different thicknesses and at several tip-sample distances. PMID:21864778

Schwartz, G A; Riedel, C; Arinero, R; Tordjeman, Ph; Alegría, A; Colmenero, J

2011-07-01

124

Capacity analysis for pulse amplitude modulated visible light communications with dimming control.  

Science.gov (United States)

This paper focuses on the capacity-approaching, nonuniform signaling for the pulse amplitude modulated (PAM) visible light communications under the non-negativity, peak power, and dimmable average power constraints. The input distribution is characterized by three parameters, i.e., the intensities, the probabilities, and the number of mass points in the PAM constellation. In the open literature, no analytical expression can be used to obtain the capacity-achieving input distribution. In this paper, a computationally simple but capacity-approaching input distribution is alternatively derived by determining the three aforementioned parameters. The resulting input distribution can serve as a useful tool not to approach the channel capacity but to guide the practical system design. Numerical results substantiate that the derived input distribution is a capacity-approaching distribution and can offer a better performance gain in comparison with the commonly employed uniform input distribution. PMID:24690654

Wang, Jin-Yuan; Wang, Jun-Bo; Huang, Nuo; Chen, Ming

2014-03-01

125

Decoding Finger Flexion using amplitude modulation from band-specific ECoG  

CERN Multimedia

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

126

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 was also included. The results indicated significant reduction in the linear growth and biomass gain of S. rolfsii after being exposed to square AM waves for 24 h in vivo or in vitro. The number of sclerotia, percentage of germination and germ tuble length was dramatically affected. Sensitization of the fungus for 24 h counteracted the potency of the fungus exposed to frequencies above 0.5 Hz 5.0 and 15 Hz were even stimulatory to seedling emergence of sugarbeet to values around the control non-infected plants.

Mohamed A. Rizk

2003-01-01

127

Tight focus of a radially polarized and amplitude-modulated annular multi-Gaussian beam  

International Nuclear Information System (INIS)

The focusing of a radially polarized beam without annular apodization ora phase filter at the entrance pupil of the objective results in a wide focus and low purity of the longitudinally polarized component. However, the presence of a physical annular apodization or phase filter makes some applications more difficult or even impossible. We propose a radially polarized and amplitude-modulated annular multi-Gaussian beam mode. Numerical simulation shows that it can be focused into a sharper focal spot of 0.125?2 without additional apodizations or filters. The beam quality describing the purity of longitudinally polarized component is up to 86%. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

2011-11-01

128

Mechanics of interaction and atomic-scale wear of amplitude modulation atomic force microscopy probes.  

Science.gov (United States)

Wear is one of the main factors that hinders the performance of probes for atomic force microscopy (AFM), including for the widely used amplitude modulation (AM-AFM) mode. Unfortunately, a comprehensive scientific understanding of nanoscale wear is lacking. We have developed a protocol for conducting consistent and quantitative AM-AFM wear experiments. The protocol involves controlling the tip-sample interaction regime during AM-AFM scanning, determining the tip-sample contact geometry, calculating the peak repulsive force and normal stress over the course of the wear test, and quantifying the wear volume using high-resolution transmission electron microscopy imaging. The peak repulsive tip-sample interaction force is estimated from a closed-form equation accompanied by an effective tip radius measurement procedure, which combines transmission electron microscopy and blind tip reconstruction. The contact stress is estimated by applying Derjaguin-Müller-Toporov contact mechanics model and also numerically solving a general contact mechanics model recently developed for the adhesive contact of arbitrary axisymmetric punch shapes. We discuss the important role that the assumed tip shape geometry plays in calculating both the interaction forces and the contact stresses. Contact stresses are significantly affected by the tip geometry while the peak repulsive force is mainly determined by experimentally controlled parameters, specifically, the free oscillation amplitude and amplitude ratio. The applicability of this protocol is demonstrated experimentally by assessing the performance of diamond-like carbon-coated and silicon-nitride-coated silicon probes scanned over ultrananocrystalline diamond substrates in repulsive mode AM-AFM. There is no sign of fracture or plastic deformation in the case of diamond-like carbon; wear could be characterized as a gradual atom-by-atom process. In contrast, silicon nitride wears through removal of the cluster of atoms and plastic deformation. PMID:23506316

Vahdat, Vahid; Grierson, David S; Turner, Kevin T; Carpick, Robert W

2013-04-23

129

Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications  

Directory of Open Access Journals (Sweden)

Full Text Available We propose a novel differential amplitude pulse-position modulation (DAPPM for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM ? in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR. The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM ? depending on the number of amplitude levels A and the maximum length L of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about 1?dB and 1.5?dB more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM 2 . When the number of bits per symbol is the same, PAM requires more power, and DH-PIM 2 less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.

Sethakaset Ubolthip

2005-01-01

130

Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications  

Directory of Open Access Journals (Sweden)

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

Sethakaset Ubolthip

2005-01-01

131

Terminal residue hydrophobicity modulates transmembrane helix-helix interactions.  

Science.gov (United States)

Central to the formation of tertiary structure in membrane protein folding is the presence of amino acid sequence motifs (such as "small-XXX-small" segments) in the TM segments that promote interaction-compatible surfaces through which the TM ?-helices interact. Here, we sought to elucidate additional factors that may work in tandem to dictate the ultimate interaction fate of TM-embedded segments. In this context, we used proteolipid protein (PLP), the major protein from central nervous system myelin for which mutant-dependent non-native oligomerization has been implicated in neurological disorders, to explore the specific effects of TM boundary residues (the membrane entry and exit points), keying on the secondary structure and self-association of peptides corresponding to the PLP TM2 ?-helix (wild-type sequence (66)AFQYVIYGTASFFFLYGALLLAEGF(90)). Using gel electrophoresis, circular dichroism, and Förster resonance energy transfer in the membrane-mimetic detergent sodium dodecyl sulfate (SDS), we found that mutation of F90 to residues such as A, I, L, or V maintains the onset of TM2-TM2 dimerization, whereas mutation to E, G, Q, N, S, or T abrogates dimer formation. We attribute this sensitivity to changes in local hydrophobicity, viz., a decrease in hydrophobicity reduces local lipid-peptide interactions, which in turn disrupts peptide ?-helicity and hence the effectiveness of an incipient interaction-compatible surface. Our results show that the secondary structure and oligomeric state of PLP TM2 Lys-tagged peptides are significantly modulated by the specific nature of their C-terminal boundary residue, thus providing insight as to how point mutations, particularly where they produce disease states, can compromise the folding process. PMID:24857611

Ng, Derek P; Deber, Charles M

2014-06-17

132

Tip motion in amplitude modulation (tapping-mode) atomic-force microscopy: Comparison between continuous and point-mass models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss the influence of high-order frequency components in the operation of an amplitude modulation atomic-force microscope (AFM). A comparative study of point-mass and continuous models is performed to describe the tip motion. The tip–surface interaction force excites high-order frequency components whenever a higher harmonic of the excitation force is close to an eigenmode of the cantilever beam. The strength of those components depends on the set point amplitude and the fundamental r...

Rodri?guez, Toma?s R.; Garci?a Garci?a, Ricardo

2002-01-01

133

Mapping the local shear modulus and viscosity using a transient finite-amplitude modulated radiation force.  

Science.gov (United States)

Localized narrowband low-frequency shear waves can be non-invasively generated within tissue, by a modulated finite-amplitude radiation force, resulting from the interference of two focused quasi-CW ultrasound beams of slightly different frequencies. Assuming a Voigt viscoelastic model, this paper describes the use of a finite-element-method model, to simulate two-dimensional shear-wave propagation in viscoelastic media, containing circular inclusions (lesions). Using this model, an inverse approach is used to extract maps of the local shear modulus and viscosity. The performance is evaluated based on three metrics: the lesion contrast, the contrast-transfer-efficiency (CTE), and the contrast-to-noise ratio (CNR). Modified definitions of these metrics are proposed and used in order to account for the time-varying nature of the shear waves and the inverse reconstruction algorithm. In the absence of any noise, it is shown that accurate reconstruction can be achieved not only with the fundamental, but also with the higher harmonics, as well as, with a low-frequency component that occurs for high viscosity and high modulation frequencies. For low-viscosity conditions, the lesion contrast, CTE, and CNR are shown to exhibit very good performance not only for the fundamental, but also, for the higher harmonics. In the case of increased viscosities and modulation frequencies, the generated low-frequency component is shown to provide superior contrast performance even when compared to that of the fundamental. The effects of noise on the reconstruction quality are examined. Depending on the lesion and background properties, it is shown that noise can seriously degrade reconstruction from the higher harmonics. PMID:21106214

Giannoula, Alexia; Cobbold, Richard S C

2011-04-01

134

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

Science.gov (United States)

Advanced multi-level modulation is an attractive modulation technique for beyond 100 Gbps short reach optical transmission system. Above all, discrete multi-tone (DMT) technique and pulse amplitude modulation (PAM) technique are the strong candidates. We compared the 100 Gbps transmission characteristics of DMT and PAM by simulation and experiment. The comparison was done by using same devices and only the digital signal processing was changed. We studied the transmission distance dependence for 0.5 to 40 km and the impact of the frequency responses of the optical devices. Finally we discuss the features of the both modulation techniques.

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

2013-12-01

135

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

Directory of Open Access Journals (Sweden)

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

Ramadan Ali

2010-01-01

136

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

137

Amplitude modulation of charge-density-wave domains in 1T-TaS sub 2 at 300 K  

Energy Technology Data Exchange (ETDEWEB)

Measurements of the charge-density-wave (CDW) amplitude modulation in 1T-TaS{sub 2} 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.

Coleman, R.V.; McNairy, W.W.; Slough, C.G.

1991-01-01

138

Amplitude modulation of charge-density-wave domains in 1T-TaS{sub 2} at 300 K  

Energy Technology Data Exchange (ETDEWEB)

Measurements of the charge-density-wave (CDW) amplitude modulation in 1T-TaS{sub 2} 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.

Coleman, R.V.; McNairy, W.W.; Slough, C.G.

1991-12-31

139

Differential Amplitude Phase Shift Keying (Dapsk): A New Modulation Method For A Turbo Code In Digital Radio Broadcasting  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The multilevel modulation techniques of M–Differential Amplitude Phase Shift Keying (DAPSK) have been proposed in combination with Turbo code scheme for digital radio broadcasting bands below 30 MHz radio channel. Comparison of this modulation method with channel coding in an Additive White Gaussian Noise (AWGN) and multi–path–fading channels has been presented. The analysis provides an iterative decoding of the Turbo code.

Sayhood, K. H.

2003-01-01

140

Stark shift in multiple quantum well structures containing a delta-doping superlattice for amplitude modulation  

International Nuclear Information System (INIS)

Full text: Batty and Allsopp [1]ha ve theoretically predicted that the introduction of an nipi delta-doping superlattice in a MQW structure may double the Stark shift, which could be advantageous for optical communication. GaAs/AlGaAs MQW structures have been grown with Si delta layers centered in the QWs and with C delta layers centered in the barriers, to try to observe such effect. For applications in amplitude modulators, where the MQWs form the intrinsic active region of the device, it is crucial that the net doping corresponds to an undoped structure, otherwise, no Stark shift can be observed. However, it has already been shown that to achieve a balance between the n and the p doping levels is quite complicated [2], making it almost impossible to observe any Stark shift. In this communication, we report for the first time the experimental observation of a Stark shift for a GaAs/AlGaAs MQW structure containing an nipi delta-doping superlattice. From photocurrent measurements as a function of the applied voltage, the Stark shift was determined to be around 6 meV for an electric field of 58 KV/cm, equivalent to that of a reference undoped MQW sample. Even though this value is still a factor of two below that previously predicted [1], it shows that it is possible to fabricate amplitude modulators using an nipi delta-doping superlattice in a MQW structure. Moreover, from the experimental data, the chirp parameter was calculated. In optical communication systems it is important that the chirp parameter, which measures the change in refractive index per change in absorption coefficient, be between 0 and -1 to compensate for the positive fiber dispersion. A chirp parameter within this range was obtained, contrary to the value of + 1.8 for the reference sample, showing that such device, as a whole, may perform better. [1]W . Batty and D. W. E. Allsopp, Electronics Letters 29, 2066 (1993). [2]C. V.-B. Tribuzy, M. P. Pires, R. Butendeich, S. M. Landi, P. L. Souza, G. E. Marques, A. C. Bittencourt and A. B. Henriques, Physica E 11, 261 (2001). (author)

2003-05-06

 
 
 
 
141

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

DEFF Research Database (Denmark)

We experimentally demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs. © 2011 Optical Society of America.

Rodes Lopez, Roberto; Pham, Tien Thang

2011-01-01

142

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

Science.gov (United States)

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

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

2013-10-30

143

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2009-01-01

144

Determination of the partial contributions of photomultiplier electrodes in the pulse amplitude distribution by the double modulation method  

International Nuclear Information System (INIS)

A technique for determining a source of dark and light pulses on photomultiplier electrodes is considered. A principal flowsheet of a device for measuring amplitude distribution of photomultiplier output pulses appearing due to photo- or dark electron emission from its electrodes is given. A double modulation method, i. e. the simuttaneous modutation of a potentiat of the dynode unOer investigation and light flux incident on the photomultiplier, is realized in the device. Frequencaes of the dynode potential and the light flux modulation are equal to 300 and 30 Hz, correspondingly. The device arrangement permits to determine the source of electrons among first four electrodes. Experimental amplitude distributions for FEhU-116 are given. This data prove that when exciting with ultraviolet radiation (250 nm), photocathode emits mainly, and in the green region that is the inner modulator of the photomultiplier

1981-01-01

145

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

146

Hindlimb movement in the cat induced by amplitude-modulated stimulation using extra-spinal electrodes  

Science.gov (United States)

Hindlimb movement in the cat induced by electrical stimulation with an amplitude-modulated waveform of the dorsal surface of the L5-S1 spinal cord or the L5-S1 dorsal/ventral roots was investigated before and after acute spinal cord transection at the T13-L1 level. Stimulation of the spinal cord or dorsal/ventral root at the same spinal segment induced similar movements including coordinated multi-joint flexion or extension. The induced movements changed from flexion to extension when the stimulation was moved from rostral (L5) to caudal (S1) spinal segments. Stimulation of a dorsal or ventral root on one side induced only ipsilateral hindlimb movement. However, stimulation on the dorsal surface of the spinal cord along the midline or across the spinal cord induced bilateral movements. The extension induced by stimulation of L7 dorsal root produced the largest ground reaction force that was strong enough to support body weight. Dorsal root stimulation induced a larger ground reaction force than ventral root stimulation and produced a more graded recruitment curve. Stepping at different speeds could be generated by combined stimulation of the rostral (L5) and the caudal (L6/L7) spinal segments with an appropriate timing between the different stimulation channels. Acute transection of the spinal cord did not change the responses indicating that the induced movements did not require the involvement of the supraspinal locomotor centers. The methods and the stimulation strategy developed in this study might be utilized to restore locomotor function after spinal cord injury.

Tai, Changfeng; Wang, Jicheng; Shen, Bing; Wang, Xianchun; Roppolo, James R.; de Groat, William C.

2008-06-01

147

Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds  

Science.gov (United States)

The ability to locate the direction of a target sound in a background of competing sources is critical to the survival of many species and important for human communication. Nevertheless, brain mechanisms that provide for such accurate localization abilities remain poorly understood. In particular, it remains unclear how the auditory brain is able to extract reliable spatial information directly from the source when competing sounds and reflections dominate all but the earliest moments of the sound wave reaching each ear. We developed a stimulus mimicking the mutual relationship of sound amplitude and binaural cues, characteristic to reverberant speech. This stimulus, named amplitude modulated binaural beat, allows for a parametric and isolated change of modulation frequency and phase relations. Employing magnetoencephalography and psychoacoustics it is demonstrated that the auditory brain uses binaural information in the stimulus fine structure only during the rising portion of each modulation cycle, rendering spatial information recoverable in an otherwise unlocalizable sound. The data suggest that amplitude modulation provides a means of “glimpsing” low-frequency spatial cues in a manner that benefits listening in noisy or reverberant environments.

Dietz, Mathias; Marquardt, Torsten; Salminen, Nelli H.; McAlpine, David

2013-01-01

148

Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds.  

Science.gov (United States)

The ability to locate the direction of a target sound in a background of competing sources is critical to the survival of many species and important for human communication. Nevertheless, brain mechanisms that provide for such accurate localization abilities remain poorly understood. In particular, it remains unclear how the auditory brain is able to extract reliable spatial information directly from the source when competing sounds and reflections dominate all but the earliest moments of the sound wave reaching each ear. We developed a stimulus mimicking the mutual relationship of sound amplitude and binaural cues, characteristic to reverberant speech. This stimulus, named amplitude modulated binaural beat, allows for a parametric and isolated change of modulation frequency and phase relations. Employing magnetoencephalography and psychoacoustics it is demonstrated that the auditory brain uses binaural information in the stimulus fine structure only during the rising portion of each modulation cycle, rendering spatial information recoverable in an otherwise unlocalizable sound. The data suggest that amplitude modulation provides a means of "glimpsing" low-frequency spatial cues in a manner that benefits listening in noisy or reverberant environments. PMID:23980161

Dietz, Mathias; Marquardt, Torsten; Salminen, Nelli H; McAlpine, David

2013-09-10

149

Resonant and Non-Resonant Modulated Amplitude Waves for Binary Bose-Einstein Condensates in Optical Lattices  

CERN Document Server

We consider a system of two Gross-Pitaevskii (GP) equations, in the presence of an optical-lattice (OL) potential, coupled by both nonlinear and linear terms. This system describes a Bose-Einstein condensate (BEC) composed of two different spin states of the same atom which interact linearly through a resonant electromagnetic field. In the absence of the OL, plane-wave solutions are found, and their stability is examined. In the presence of the OL, we derive a system of amplitude equations for spatially modulated states which are coupled to the periodic potential through the lowest-order subharmonic resonance. We determine this system's equilibria, which represent spatially periodic solutions and subsequently examine stability of the corresponding solutions by direct simulations of the coupled GP equations. We find that symmetric (equal amplitude) and asymmetric (unequal amplitude) dual-mode resonant states are, respectively, stable and unstable. The unstable state generates periodic oscillations between the ...

Porter, M A; Malomed, B A; Porter, Mason A.

2004-01-01

150

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

International Nuclear Information System (INIS)

The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection (DPD) method in the signal waveform modulation multi-level (SWML) read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc. (classical areas of phenomenology)

2010-10-01

151

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

Science.gov (United States)

The effects of amplitude modulation (AM) on an atmospheric pressure microwave argon jet is investigated using time-resolved optical emission spectroscopy, passive acoustic diagnostic and digital camera imaging. These techniques show significant changes of the effluent plasma properties with varying AM frequency. Operation in AM mode can enhance the plasma jet length or width over continuous-wave mode with the same mean power, which could be advantageous in many practical applications of plasma jets.

Hnilica, J.; Kudrle, V.

2014-02-01

152

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

International Nuclear Information System (INIS)

Cerebral cortex tissue slices and cerebral hemispheres prepared from Gallus domesticus chicks were exposed to 147 MHz radiofrequency radiation, amplitude modulated at 16 Hz and applied at a power density of 0.75 mW/cm2, to determine the effect of such exposure of "4"5Ca"2"+ efflux from the avian brain tissue. Statistical analysis of these data demonstrates that such exposure has no significant effect on "4"5Ca"2"+ efflux

1987-01-01

153

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

Science.gov (United States)

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. PMID:6487385

Brunkard, K M; Pickard, W F

1984-01-01

154

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

155

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

An accurate ultrasonic range finder employing Sliding Discrete Fourier Transform (SDFT) based restructured phase-locked loop (RPLL), which is an improved version of the recently proposed integrated phase-locking scheme (IPLL), has been expounded. This range finder principally utilizes amplitude-modulated ultrasonic waves assisted by an infrared (IR) pilot signal. The phase shift between the envelope of the reference IR pilot signal and that of the received ultrasonic signal is proportional to...

Sumathi, P.; Janakiraman, P. A.

2010-01-01

156

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

International Nuclear Information System (INIS)

Highlights: •Our study addressed the toxicity thresholds of uranium on microalgae using PAM fluorometry. •The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium. •Uranium impaired the electron flux between the photosystems until almost complete inhibition. •Non-photochemical quenching was identified as the most sensitive fluorescence parameter. •PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response. -- Abstract: Although ecotoxicological studies tend to address the toxicity thresholds of uranium in freshwaters, there is a lack of information on the effects of the metal on physiological processes, particularly in aquatic plants. Knowing that uranium alters photosynthesis via impairment of the water photo-oxidation process, we determined whether pulse amplitude modulated (PAM) fluorometry was a relevant tool for assessing the impact of uranium on the green alga Chlamydomonas reinhardtii and investigated how and to what extent uranium hampered photosynthetic performance. Photosynthetic activity and quenching were assessed from fluorescence induction curves generated by PAM fluorometry, after 1 and 5 h of uranium exposure in controlled conditions. The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium, through alteration of the water photo-oxidation process as revealed by F0/Fv. Limiting re-oxidation of the plastoquinone pool, uranium impaired the electron flux between the photosystems until almost complete inhibition of the PSII quantum efficiency (F?q/F?m, EC50 = 303 ± 64 ?g U L?1 after 5 h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC50 = 142 ± 98 ?g U L?1 after 5 h of exposure), indicating that light energy not used in photochemistry was dissipated in non-radiative processes. It was shown that parameters which stemmed from fluorescence induction kinetics are valuable indicators for evaluating the impact of uranium on PSII in green algae. PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response to uranium in microalgae

2013-09-15

157

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-09-15

158

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

Directory of Open Access Journals (Sweden)

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

Mohammud Ershadul Haque

2013-01-01

159

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

CERN Document Server

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

Anderson, Richard I

2014-01-01

160

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

Science.gov (United States)

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

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

2011-07-01

 
 
 
 
161

Unilateral Auditory Cortex Lesions Impair or Improve Discrimination Learning of Amplitude Modulated Sounds, Depending on Lesion Side  

Science.gov (United States)

A fundamental principle of brain organization is bilateral symmetry of structures and functions. For spatial sensory and motor information processing, this organization is generally plausible subserving orientation and coordination of a bilaterally symmetric body. However, breaking of the symmetry principle is often seen for functions that depend on convergent information processing and lateralized output control, e.g. left hemispheric dominance for the linguistic speech system. Conversely, a subtle splitting of functions into hemispheres may occur if peripheral information from symmetric sense organs is partly redundant, e.g. auditory pattern recognition, and therefore allows central conceptualizations of complex stimuli from different feature viewpoints, as demonstrated e.g. for hemispheric analysis of frequency modulations in auditory cortex (AC) of mammals including humans. Here we demonstrate that discrimination learning of rapidly but not of slowly amplitude modulated tones is non-uniformly distributed across both hemispheres: While unilateral ablation of left AC in gerbils leads to impairment of normal discrimination learning of rapid amplitude modulations, right side ablations lead to improvement over normal learning. These results point to a rivalry interaction between both ACs in the intact brain where the right side competes with and weakens learning capability maximally attainable by the dominant left side alone.

Schulze, Holger; Deutscher, Anke; Tziridis, Konstantin; Scheich, Henning

2014-01-01

162

Cross-polarization with radio-frequency field phase and amplitude modulation under magic-angle spinning conditions  

International Nuclear Information System (INIS)

Nucleus cross-polarization technique in a rotating frame of reference is analyzed as applied to NMR experiments with sample magic-angle spinning. The concept of simultaneous phase and amplitude modulation is suggested. According to this suggestion, the form of the Hamiltonian of recoupled dipolar interaction remains unchanged if phase inversion is accompanied by inversion of the difference of radio-frequency (RF) field amplitudes. A theoretical treatment is given in terms of the average Hamiltonian theory. The concept is demonstrated experimentally and by numerical analysis for several particular cases. Periodic phase inversion in cross-polarization experiments was shown to have the practically important advantage of suppressing chemical shift interactions and the effect of inaccurate tuning of RF field parameters

2006-01-01

163

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

164

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 was also included. The results indicated significant reduction in the linear growth and biomass gain of S. rolfsii after being exposed to square AM waves for 24 h in vivo or in vitr...

Rizk, Mohamed A.

2003-01-01

165

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

Science.gov (United States)

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

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

2013-08-01

166

Improvement of the Spatial Amplitude Isotropy of a 4He Magnetometer Using a Modulated Pumping Beam  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Optically pumped magnetometers are scalar magnetometers. Contrary to vectoriel magnetometers, they measure the total magnetic field whatever the direction of the sensor. However, for some orientations of the magnetometer with respect to the magnetic field direction, the resonant signal vanishes and the measurement is impossible. In this paper we present a simple solution to reduce the amplitude spatial anisotropy and apply it to a 4He magnetometer developed in our Laboratory.

Che?ron, B.; Gilles, H.; Hamel, J.; Moreau, O.; Noe?l, E.

1997-01-01

167

Motivation modulates the P300 amplitude during brain-computer interface use  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objective: This study examined the effect of motivation as a possible psychological influencing variable on P300 amplitude and performance in a brain-computer interface (BCI) controlled by event-related potentials (ERP). Methods: Participants were instructed to copy spell a sentence by attending to cells of a randomly flashing 7 * 7 matrix. Motivation was manipulated by monetary reward. In two experimental groups participants received 25 (N = 11) or 50 (N = 11) Euro cent for each correctly se...

Kleih, S. C.; Nijboer, F.; Halder, S.; Kuebler, A.

2010-01-01

168

Techniques for Effective Optical Noise Rejection in Amplitude-Modulated Laser Optical Radars for Underwater Three-Dimensional Imaging  

Directory of Open Access Journals (Sweden)

Full Text Available Amplitude-modulated (AM laser imaging is a promising technology for the production of accurate three-dimensional (3D images of submerged scenes. The main challenge is that radiation scattered off water gives rise to a disturbing signal (optical noise that degrades more and more the quality of 3D images for increasing turbidity. In this paper, we summarize a series of theoretical findings, that provide valuable hints for the development of experimental methods enabling a partial rejection of optical noise in underwater imaging systems. In order to assess the effectiveness of these methods, which range from modulation/demodulation to polarimetry, we carried out a series of experiments by using the laboratory prototype of an AM 3D imager ( = 405?nm for marine archaeology surveys, in course of realization at the ENEA Artificial Vision Laboratory (Frascati, Rome. The obtained results confirm the validity of the proposed methods for optical noise rejection.

Francucci M

2010-01-01

169

Techniques for Effective Optical Noise Rejection in Amplitude-Modulated Laser Optical Radars for Underwater Three-Dimensional Imaging  

Directory of Open Access Journals (Sweden)

Full Text Available Amplitude-modulated (AM laser imaging is a promising technology for the production of accurate three-dimensional (3D images of submerged scenes. The main challenge is that radiation scattered off water gives rise to a disturbing signal (optical noise that degrades more and more the quality of 3D images for increasing turbidity. In this paper, we summarize a series of theoretical findings, that provide valuable hints for the development of experimental methods enabling a partial rejection of optical noise in underwater imaging systems. In order to assess the effectiveness of these methods, which range from modulation/demodulation to polarimetry, we carried out a series of experiments by using the laboratory prototype of an AM 3D imager (? = 405?nm for marine archaeology surveys, in course of realization at the ENEA Artificial Vision Laboratory (Frascati, Rome. The obtained results confirm the validity of the proposed methods for optical noise rejection.

R. Ricci

2010-01-01

170

Excitation of periodic magnetic field oscillations in the ULF range by amplitude modulated HF waves  

International Nuclear Information System (INIS)

High power HF radio waves radiated into the ionosphere strongly enhance the electron temperature. This electron heating can cause perturbations in the conductivity tensor via an enhancement of the collision frequency or the electron density, depending on the modulation frequency of the HF wave. The periodically altered conductivities result in an ac current that emits electromagnetic waves. Two experiments with modulation frequencies between 0.7 and 9 Hz, and one with frequencies of 1425 Hz, 1 Hz, and 8.33 mHz are studied in detail and compared with numerical calculations. It is found that ellipticity and orientation of the polarization ellipse of the measured magnetic wave field can be ascribed to the effects of the temperature and density modulation

1990-01-01

171

Low-bias terahertz amplitude modulator based on split-ring resonators and graphene.  

Science.gov (United States)

Split-ring resonators represent the ideal route to achieve optical control of the incident light at THz frequencies. These subwavelength metamaterial elements exhibit broad resonances that can be easily tuned lithographically. We have realized a design based on the interplay between the resonances of metallic split rings and the electronic properties of monolayer graphene integrated in a single device. By varying the major carrier concentration of graphene, an active modulation of the optical intensity was achieved in the frequency range between 2.2 and 3.1 THz, achieving a maximum modulation depth of 18%, with a bias as low as 0.5 V. PMID:24558983

Degl'Innocenti, Riccardo; Jessop, David S; Shah, Yash D; Sibik, Juraj; Zeitler, J Axel; Kidambi, Piran R; Hofmann, Stephan; Beere, Harvey E; Ritchie, David A

2014-03-25

172

An integrated program for amplitude-modulated RF pulse generation and re-mapping with shaped gradients.  

Science.gov (United States)

Efficient generation of amplitude modulated, frequency selective RF pulses has been demonstrated by the Shinnar-Le Roux (SLR) algorithm. In the present article, we provide an overview of a relatively comprehensive computer program that includes a version of the SLR algorithm and also incorporates an algorithm for re-mapping a selective RF pulse onto a new dwell time with modulated gradients. The re-mapping may be used to reduce SAR, or to shorten the RF pulse time by increasing the gradient and RF strength in regions where the original RF pulse amplitude was low. The program includes additional useful features including a Bloch equations algorithm, and pulse scaling, to enable examination of pulse profiles under a variety of conditions such as RF inhomogeneity and even nuclear relaxation. The program, MATPULSE, was developed with the MATLAB for Windows programming language and makes extensive use of the MATLAB graphical user interface (GUI) features to generate a user-friendly interface. A number of examples are provided to illustrate the capabilities of the MATPULSE program. PMID:7854027

Matson, G B

1994-01-01

173

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

Directory of Open Access Journals (Sweden)

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

Korman Maria

2011-12-01

174

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

175

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

Energy Technology Data Exchange (ETDEWEB)

Mechanical surface treatments such as deep rolling are known to affect the near-surface microstructure and induce, e.g. residual stresses and/or increase the surface hardness. It is well known that, e.g. compressive residual stress states usually increase the lifetime under fatigue loading. The stress relaxation behaviour and the stability of the residual stress during fatigue loading depend on the mechanical surface treatment method. In this paper three different surface treatments are used and their effects on the low cycle fatigue behaviour of austenitic stainless steel (AISI 304) and ferritic-pearlitic steel (SAE 1045) are investigated. X-ray diffraction is applied for the non-destructive evaluation of the stress state and the microstructure. It is found that consecutive deep rolling and annealing as well as high temperature deep rolling produce more stable near-surface stress states than conventional deep rolling at room temperature. The plastic strain amplitudes during fatigue loading are measured and it is shown that they correlate well with the induced residual stress and its relaxation, respectively. Furthermore, Coffin-Manson plots are presented which clearly show the correlation between the plastic strain amplitude and the fatigue lifetime.

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

2008-09-15

176

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

International Nuclear Information System (INIS)

Mechanical surface treatments such as deep rolling are known to affect the near-surface microstructure and induce, e.g. residual stresses and/or increase the surface hardness. It is well known that, e.g. compressive residual stress states usually increase the lifetime under fatigue loading. The stress relaxation behaviour and the stability of the residual stress during fatigue loading depend on the mechanical surface treatment method. In this paper three different surface treatments are used and their effects on the low cycle fatigue behaviour of austenitic stainless steel (AISI 304) and ferritic-pearlitic steel (SAE 1045) are investigated. X-ray diffraction is applied for the non-destructive evaluation of the stress state and the microstructure. It is found that consecutive deep rolling and annealing as well as high temperature deep rolling produce more stable near-surface stress states than conventional deep rolling at room temperature. The plastic strain amplitudes during fatigue loading are measured and it is shown that they correlate well with the induced residual stress and its relaxation, respectively. Furthermore, Coffin-Manson plots are presented which clearly show the correlation between the plastic strain amplitude and the fatigue lifetime

2008-09-15

177

Controlled transfer of quantum amplitude via modulation of a potential barrier: numerical study in a model of SQUID  

Energy Technology Data Exchange (ETDEWEB)

We numerically integrate the time-dependent Schroedinger equation in a single-degree-of-freedom model of SQUID with a variable potential barrier between the basis flux states. We find that linear superpositions of the basis states, with relatively little residual excitation, can be formed by pulsed modulations of the barrier, provided the pulse duration exceeds the period of small oscillations of the flux. Two pulses applied in sequence exhibit strong interference effects, which we propose to use for an experimental determination of the decoherence time in SQUIDs. (author)

Crogan, M. [Department of Physics, Purdue University, West Lafayette, IN (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN (United States); Khlebnikov, S. [Department of Physics, Purdue University, West Lafayette, IN (United States); Sadiek, G. [Department of Physics, Purdue University, West Lafayette, IN (United States)

2002-01-01

178

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

Science.gov (United States)

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.

Shih, Po-Jen

2012-01-01

179

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

2012-05-01

180

High resolution imaging of immunoglobulin G antibodies and other biomolecules using amplitude modulation atomic force microscopy in air.  

Science.gov (United States)

The atomic force microscope (AFM) is a very versatile tool for studying biological samples at -nanometre-scale resolution. The resolution one achieves depends on many factors, including the sample properties, the imaging environment, the AFM tip and cantilever probe characteristics, and the signal detection and feedback control mechanism, to name a few. This chapter describes how to routinely achieve the highest possible spatial resolution on isolated protein molecules on mica surfaces. This is illustrated with Immunoglobulin G antibodies but the methods apply equally well to any other globular multi-subunit protein, as well as other biomolecules. Double-stranded DNA is used as a model sample to illustrate the effects of the force regime in amplitude modulation atomic force microscopy (AM AFM) on the image resolution and contrast. AM control is a widely used technique in biological AFM for reasons which are discussed. PMID:21660721

Santos, Sergio; Thomson, Neil H

2011-01-01

 
 
 
 
181

A Fault-tolerant 32 nm CMOS Double Sideband Amplitude Suppressed Carrier Modulator-Demodulator Circuit Implementation  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a low-voltage, low-power and fault-tolerant implementation of Double Sideband Suppressed Carrier (DSB-SC amplitude modulator-demodulator circuit for portable communication systems. Through the approximation proposed in this work, a CMOS four quadrant multiplier is used as a (demodulator circuit to generate DSB-SC (demodulated signals. Furthermore, the proposed fault-tolerant modem can be used to enhance the reliability of safety-critical communication systems since it is able to provide duplicated output using two path output computations. The proposed circuit occupies a small surface area and is functional at high frequencies even with a low supply voltage. SPICE simulations of the post-layout extracted CMOS multiplier in a full-custom 32 nm CMOS technology, which include all parasitic, are used to demonstrate the electrical behavior of the circuit.

Mouna Karmani

2012-05-01

182

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

Science.gov (United States)

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

Vahdat, Vahid; Carpick, Robert W

2013-11-26

183

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

Scientific Electronic Library Online (English)

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

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

184

Antibody responses of mice exposed to low-power microwaves under combined, pulse-and-amplitude modulation  

Energy Technology Data Exchange (ETDEWEB)

Irradiation by pulsed microwaves (9.4 GHz, 1 microsecond pulses at 1,000/s), both with and without concurrent amplitude modulation (AM) by a sinusoid at discrete frequencies between 14 and 41 MHz, was assessed for effects on the immune system of Balb/C mice. The mice were immunized either by sheep red blood cells (SRBC) or by glutaric-anhydride conjugated bovine serum albumin (GA-BSA), then exposed to the microwaves at a low rms power density (30 microW/cm2; whole-body-averaged SAR approximately 0.015 W/kg). Sham exposure or microwave irradiation took place during each of five contiguous days, 10 h/day. The antibody response was evaluated by the plaque-forming cell assay (SRBC experiment) or by the titration of IgM and IgG antibodies (GA-BSA experiment). In the absence of AM, the pulsed field did not greatly alter immune responsiveness. In contrast, exposure to the field under the combined-modulation condition resulted in significant, AM-frequency-dependent augmentation or weakening of immune responses.

Veyret, B.; Bouthet, C.; Deschaux, P.; de Seze, R.; Geffard, M.; Joussot-Dubien, J.; le Diraison, M.; Moreau, J.M.; Caristan, A.

1991-01-01

185

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

CERN Multimedia

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

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

2013-01-01

186

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

Science.gov (United States)

Context. Classical Cepheids are crucial calibrators of the extragalactic distance scale. The Baade-Wesselink technique can be used to calibrate Cepheid distances using Cepheids in the Galaxy and the Magellanic Clouds. Aims: I report the discovery of modulations in radial velocity (RV) curves of four Galactic classical Cepheids and investigate their impact as a systematic uncertainty for Baade-Wesselink distances. Methods: Highly precise Doppler measurements were obtained using the Coralie high-resolution spectrograph since 2011. Particular care was taken to sample all phase points in order to very accurately trace the RV curve during multiple epochs and to search for differences in linear radius variations derived from observations obtained at different epochs. Different timescales are sampled, ranging from cycle-to-cycle to months and years. Results: The unprecedented combination of excellent phase coverage obtained during multiple epochs and high precision enabled the discovery of significant modulation in the RV curves of the short-period s-Cepheids QZ Normae and V335 Puppis, as well as the long-period fundamental mode Cepheids ? Carinae and RS Puppis. The modulations manifest as shape and amplitude variations that vary smoothly on timescales of years for short-period Cepheids and from one pulsation cycle to the next in the long-period Cepheids. The order of magnitude of the effect ranges from several hundred m s-1 to a few km s-1. The resulting difference among linear radius variations derived using data from different epochs can lead to systematic errors of up to 15% for Baade-Wesselink-type distances, if the employed angular and linear radius variations are not determined contemporaneously. Conclusions: The different natures of the Cepheids exhibiting modulation in their RV curves suggests that this phenomenon is common. The observational baseline is not yet sufficient to conclude whether these modulations are periodic. To ensure the accuracy of Baade-Wesselink distances, angular and linear radius variations should always be determined contemporaneously. Based on observations collected at ESO La Silla Observatory using the Coralie spectrograph mounted to the Swiss 1.2 m Euler telescope.The derived radial velocities are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/L10Appendix A is available in electronic form at http://www.aanda.org

Anderson, Richard I.

2014-06-01

187

The substructure of immunoglobulin G resolved to 25 kDa using amplitude modulation AFM in air  

International Nuclear Information System (INIS)

Amplitude modulation (or tapping-mode) atomic force microscopy (AM AFM or TM AFM) in air can reveal sub-molecular details of isolated multi-subunit proteins, such as immunoglobulin G (IgG) antibodies, on atomically flat support surfaces such as mica [A. San Paulo, R. Garcia, Biophys. J. 78(3) (2000) 1599]. This is achieved by controlling the microscope imaging parameters (e.g. cantilever drive frequency and set-point amplitude) to keep the AFM tip predominantly in the attractive force regime. Under these conditions, the 50 kDa F c and F ab subunits can be resolved when the molecule has the appropriate orientation on the surface. The presence of a water layer on hydrophilic mica is an important factor affecting imaging contrast, a consequence of capillary neck formation between tip and surface [L. Zitzler, S. Herminghaus, F. Mugele, Phys. Rev. B 66(15) (2002) 155436]. Desiccation of samples to remove surface bound water layers can yield reproducible imaging of the IgG substructure [N.H. Thomson, J. Microsc. (Oxford) 217(3) (2004) 193]. This approach has also given higher resolution than previously achieved, down to about 25 kDa, and these data are detailed here. These subdomains are formed as two immunoglobulin folds from the light and heavy peptide chains of the IgG crossover. This result has been validated by comparing the AFM images with X-ray crystallography data from the protein data bank. These data show that the AFM can obtain 25 kDa resolution on isolated protein molecules with commercially available silicon tips, but, as expected for a local probe technique, resolution is highly dependent on the macromolecular orientation on the support surface

2005-11-01

188

Characterization of deep nanoscale surface trenches with AFM using thin carbon nanotube probes in amplitude-modulation and frequency-force-modulation modes  

International Nuclear Information System (INIS)

The characterization of deep surface trenches with atomic force microscopy (AFM) presents significant challenges due to the sharp step edges that disturb the instrument and prevent it from faithfully reproducing the sample topography. Previous authors have developed AFM methodologies to successfully characterize semiconductor surface trenches with dimensions on the order of tens of nanometers. However, the study of imaging fidelity for features with dimensions smaller than 10 nm has not yet received sufficient attention. Such a study is necessary because small features in some cases lead to apparently high-quality images that are distorted due to tip and sample mechanical deformation. This paper presents multi-scale simulations, illustrating common artifacts affecting images of nanoscale trenches taken with fine carbon nanotube probes within amplitude-modulation and frequency-force-modulation AFM (AM-AFM and FFM-AFM, respectively). It also describes a methodology combining FFM-AFM with a step-in/step-out algorithm analogous to that developed by other groups for larger trenches, which can eliminate the observed artifacts. Finally, an overview of the AFM simulation methods is provided. These methods, based on atomistic and continuum simulation, have been previously used to study a variety of samples including silicon surfaces, carbon nanotubes and biomolecules

2008-01-01

189

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

Science.gov (United States)

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

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

2014-01-01

190

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

Science.gov (United States)

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

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

2014-05-15

191

Use of special modules of the residue number system for redundant representation  

Directory of Open Access Journals (Sweden)

Full Text Available The residue number system (RNS, due to its properties, is used in applications in which high ac-curacy of computations is not required. Since carries are not transmitted between the moduli in the RNS, the performance is only restricted by the speed of the operations in each modulus. A new method of number representation using the redundancy is suggested in which is a set of the reference modules, where and . This method provides a signifi-cant reduction of delay of computations and conversions and leads to a simplification of schemes.

Erdnieva Nadezhda Sergeevna

2013-08-01

192

Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in static NMR of half-integer spin quadrupolar nuclei  

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In solid-state NMR of quadrupolar nuclei with half-integer spin I, fast amplitude-modulated (FAM) pulse trains have been utilised to enhance the intensity of the central-transition signal, by transferring spin population from the satellite transitions. In this paper, the signal-enhancement performance of the recently introduced SW-FAM pulse train with swept modulation frequency [T. Bräuniger, K. Ramaswamy, P.K. Madhu, Enhancement of the central-transition signal in static and magic-angle-spinning NMR of quadrupolar nuclei by frequency-swept fast amplitude-modulated pulses, Chem. Phys. Lett. 383 (2004) 403-410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW (1/ ?)-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SW ( ?)-FAM). For static spectra of 27Al ( I = 5/2), better signal-enhancement performance is found for the SW (1/ ?)-FAM sequence, as demonstrated both by experiments and numerical simulations.

Bräuniger, Thomas; Hempel, Günter; Madhu, P. K.

2006-07-01

193

Sets of Covariant Residues Modulate the Activity and Thermal Stability of GH1 ?-Glucosidases  

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The statistical coupling analysis of 768 ?-glucosidases from the GH1 family revealed 23 positions in which the amino acid frequencies are coupled. The roles of these covariant positions in terms of the properties of ?-glucosidases were investigated by alanine-screening mutagenesis using the fall armyworm Spodoptera frugiperda ?-glycosidase (Sf?gly) as a model. The effects of the mutations on the Sf?gly kinetic parameters (kcat/Km) for the hydrolysis of three different p-nitrophenyl ?-glycosides and structural comparisons of several ?-glucosidases showed that eleven covariant positions (54, 98, 143, 188, 195, 196, 203, 398, 451, 452 and 460 in Sf?gly numbering) form a layer surrounding the active site of the ?-glucosidases, which modulates their catalytic activity and substrate specificity via direct contact with the active site residues. Moreover, the influence of the mutations on the transition temperature (Tm) of Sf?gly indicated that nine of the coupled positions (49, 62, 143, 188, 223, 278, 309, 452 and 460 in Sf?gly numbering) are related to thermal stability. In addition to being preferentially occupied by prolines, structural comparisons indicated that these positions are concentrated at loop segments of the ?-glucosidases. Therefore, due to these common biochemical and structural properties, these nine covariant positions, even without physical contacts among them, seem to jointly modulate the thermal stability of ?-glucosidases.

Tamaki, Fabio K.; Textor, Larissa C.; Polikarpov, Igor; Marana, Sandro R.

2014-01-01

194

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

195

Magnetic field and temperature dependence of the amplitude-modulated magnetic structure of PrNi2Si2 determined by single-crystal neutron diffraction  

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The temperature and magnetic field dependence of the magnetic structure in the singlet crystal-field ground-state system PrNi2Si2 have been determined using single-crystal neutron diffraction. At the magnetic ordering temperature in zero field, TN=20.0±0.5?K, an amplitude-modulated magnetic structure sets in with a propagation vector k=(0,0,0.87) and the magnetic moments of the Pr3+ ions parallel to the c axis of the body-centered tetragonal structure. The magnetic structure remains amplit...

Blanco, J. A.; Rodrigue?z-velamaza?n, J. A.; Campo, Javier

2010-01-01

196

Non Uniform Differential Amplitude Phase–Shift–Key (Dapsk) Modulation For Multimedia Multicast Wireless Communications With Punctured Convolutional Coding  

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Simple closed–form expressions for the probability of error for nonuniform M–ary Differential Amplitude Phase–Shift–Key (DAPSK) signaling over an Additive White Gaussian Noise (AWGN) and Rayleigh fading channels are presented. Nonuniform M–DAPSK is shown to be useful for multimedia communication and multicast transmission. The performance of nonuniform M–DAPSK with punctured convolutional coding is presented. The results show that the coding can be used with nonuniform M–DAPSK m...

Sayhood, K. H.

2003-01-01

197

Amplitude modulation of steady-state visual evoked potentials by event-related potentials in a working memory task  

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Previous studies have shown that the amplitude and phase of the steady-state visual-evoked potential (SSVEP) can be influenced by a cognitive task, yet the mechanism of this influence has not been understood. As the event-related potential (ERP) is the direct neural electric response to a cognitive task, studying the relationship between the SSVEP and ERP would be meaningful in understanding this underlying mechanism. In this work, the traditional average method was applied to extract the ERP...

Wu, Zhenghua; Yao, Dezhong; Tang, Yu; Huang, Yilan; Su, Sheng

2010-01-01

198

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

199

Mutation of outer-shell residues modulates metal ion co-ordination strength in a metalloenzyme.  

Science.gov (United States)

The metal ion co-ordination sites of many metalloproteins have been characterized by a variety of spectroscopic techniques and small-molecule model systems, revealing many important insights into the structural determinants of metal ion co-ordination. However, our understanding of this fundamentally and practically important phenomenon remains frustratingly simplistic; in many proteins it is essentially impossible to predict metal ion specificity and the effects of remote 'outer-shell' residues on metal ion co-ordination strength are also poorly defined. This is exemplified by our inability to explain why metalloenzymes with identical metal ion co-ordination spheres, such as the closely related orthologues of bacterial PTE (phosphotriesterase) from Agrobacterium radiobacter and Pseudomonas diminuta, display different metal ion specificity and co-ordination strength. In the present study, we present a series of PTE variants that all possess identical metal ion co-ordination spheres, yet display large differences in their metal ion co-ordination strength. Using measurement of the rates of metal ion dissociation from the active site alongside analysis of structural data obtained through X-ray crystallography, we show that 'outer-shell' residues provide essential support for the metal ion ligands, in effect buttressing them in their optimal orientation. Remote mutations appear to modulate metal ion interactions by increasing or decreasing the stabilizing effects of these networks. The present study therefore provides a description of how the greater protein fold can be modified to 'tune' the strength of metal ion co-ordination and metal ion specificity, as well as reinforcing the concept of proteins as ensembles of conformational states with unique structures and biochemical properties. PMID:20459397

Foo, Jee-Loon; Jackson, Colin J; Carr, Paul D; Kim, Hye-Kyung; Schenk, Gerhard; Gahan, Lawrence R; Ollis, David L

2010-07-15

200

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

Directory of Open Access Journals (Sweden)

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

Aru Okereke Eze

2014-02-01

 
 
 
 
201

The Influence of Silica Module of the Soluble Sodium Silicate Hardened by Ester on the Residual Strenght of Molding Sand  

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Full Text Available Describes how to obtain a soluble sodium silicate with a density of 1.40 g/cm3, 1.45 g/cm3, 1.50 g/cm3, and silica module M = 2.1obtained from the silica- sodium glass with module M = 3.3 and M = 2.1. Residual (final strength of molding samples made with thesebinders, were determined at temperatures corresponding to the characteristic temperatures of phase and temperature transitions of silica gel. Indicated the type of soluble sodium silicate capable of obtain the smallest value of the final strength of molding sand in the specified range of temperatures.

A. Bali?ski

2013-01-01

202

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

Science.gov (United States)

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

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

2013-02-01

203

Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in solid-state NMR of spin-7/2 nuclei  

Science.gov (United States)

We here investigate the sensitivity enhancement of central-transition NMR spectra of quadrupolar nuclei with spin-7/2 in the solid state, generated by fast amplitude-modulated RF pulse trains with constant (FAM-I) and incremented pulse durations (SW-FAM). Considerable intensity is gained for the central-transition resonance of single-quantum spectra by means of spin population transfer from the satellite transitions, both under static and magic-angle-spinning (MAS) conditions. It is also shown that incorporation of a SW-FAM train into the excitation part of a 7QMAS sequence improves the efficiency of 7Q coherence generation, resulting in improved signal-to-noise ratio. The application of FAM-type pulse trains may thus facilitate faster spectra acquisition of spin-7/2 systems.

Bräuniger, Thomas; Madhu, P. K.

2008-07-01

204

Experimental verification of low-frequency, highly-directive sound radiation in ambient air by amplitude-modulated, high-intensity ultrasonic waves  

Science.gov (United States)

A 21 kHz standing-wave amplifier at the focus of a 36 cm diameter parabolic mirror (ka=70) is used for highly directive radiation of low frequency sine waves, voice signals and even music (of poor quality). The low frequency waves are amplitude-modulated onto the ultrasonic carrier wave and radiated into a solid angle of +/-1° (-3 dB). Low frequency sound waves with frequencies between 50 Hz and 3 kHz are radiated over a distance of more than 20 m. The achievable audio sound pressure levels decrease with approximately 20 dB per distance doubling and reached about 30 dB at 20 m distance. The discussion of the measurements is based on Blackstock's weak shock theory [5] and on the nonsaturated radiation pressure at saturated sound pressure levels. .

Lierke, E. G.

2000-07-01

205

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

Science.gov (United States)

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

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

2004-10-01

206

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

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Full Text Available Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip, Mumbai (13.4° N dip and Ujjain (18.6° N dip exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not inconsistent with our observations.

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

A. K. Sinha

207

Simulation study of amplitude-modulated (AM) harmonic motion imaging (HMI) for stiffness contrast quantification with experimental validation.  

Science.gov (United States)

The objective of this study is to show that Harmonic Motion Imaging (HMI) can be used as a reliable tumor-mapping technique based on the tumor's distinct stiffness at the early onset of disease. HMI is a radiation-force-based imaging method that generates a localized vibration deep inside the tissue to estimate the relative tissue stiffness based on the resulting displacement amplitude. In this paper, a finite-element model (FEM) study is presented, followed by an experimental validation in tissue-mimicking polyacrylamide gels and excised human breast tumors ex vivo. This study compares the resulting tissue motion in simulations and experiments at four different gel stiffnesses and three distinct spherical inclusion diameters. The elastic moduli of the gels were separately measured using mechanical testing. Identical transducer parameters were used in both the FEM and experimental studies, i.e., a 4.5-MHz single-element focused ultrasound (FUS) and a 7.5-MHz diagnostic (pulse-echo) transducer. In the simulation, an acoustic pressure field was used as the input stimulus to generate a localized vibration inside the target. Radiofrequency (rf) signals were then simulated using a 2D convolution model. A one-dimensional cross-correlation technique was performed on the simulated and experimental rf signals to estimate the axial displacement resulting from the harmonic radiation force. In order to measure the reliability of the displacement profiles in estimating the tissue stiffness distribution, the contrast-transfer efficiency (CTE) was calculated. For tumor mapping ex vivo, a harmonic radiation force was applied using a 2D raster-scan technique. The 2D HMI images of the breast tumor ex vivo could detect a malignant tumor (20 x 10 mm2) surrounded by glandular and fat tissues. The FEM and experimental results from both gels and breast tumors ex vivo demonstrated that HMI was capable of detecting and mapping the tumor or stiff inclusion with various diameters or stiffnesses. HMI may thus constitute a promising technique in tumor detection (>3 mm in diameter) and mapping based on its distinct stiffness. PMID:20718245

Maleke, Caroline; Luo, Jianwen; Gamarnik, Viktor; Lu, Xin L; Konofagou, Elisa E

2010-07-01

208

Dynamics of Linker Residues Modulate the Nucleic Acid Binding Properties of the HIV-1 Nucleocapsid Protein Zinc Fingers  

Science.gov (United States)

The HIV-1 nucleocapsid protein (NC) is a small basic protein containing two zinc fingers (ZF) separated by a short linker. It is involved in several steps of the replication cycle and acts as a nucleic acid chaperone protein in facilitating nucleic acid strand transfers occurring during reverse transcription. Recent analysis of three-dimensional structures of NC-nucleic acids complexes established a new property: the unpaired guanines targeted by NC are more often inserted in the C-terminal zinc finger (ZF2) than in the N-terminal zinc finger (ZF1). Although previous NMR dynamic studies were performed with NC, the dynamic behavior of the linker residues connecting the two ZF domains remains unclear. This prompted us to investigate the dynamic behavior of the linker residues. Here, we collected 15N NMR relaxation data and used for the first time data at several fields to probe the protein dynamics. The analysis at two fields allows us to detect a slow motion occurring between the two domains around a hinge located in the linker at the G35 position. However, the amplitude of motion appears limited in our conditions. In addition, we showed that the neighboring linker residues R29, A30, P31, R32, K33 displayed restricted motion and numerous contacts with residues of ZF1. Our results are fully consistent with a model in which the ZF1-linker contacts prevent the ZF1 domain to interact with unpaired guanines, whereas the ZF2 domain is more accessible and competent to interact with unpaired guanines. In contrast, ZF1 with its large hydrophobic plateau is able to destabilize the double-stranded regions adjacent to the guanines bound by ZF2. The linker residues and the internal dynamics of NC regulate therefore the different functions of the two zinc fingers that are required for an optimal chaperone activity.

Zargarian, Loussine; Tisne, Carine; Barraud, Pierre; Xu, Xiaoqian; Morellet, Nelly; Rene, Brigitte; Mely, Yves; Fosse, Philippe; Mauffret, Olivier

2014-01-01

209

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

210

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)

In this study, atomic force microscopy (AFM) has been employed to image a photopolymerized poly(ethylene glycol) diacrylate (PEG-DA) hydrogel. The same area was imaged both in amplitude modulation (AM) and in frequency modulation (FM) mode and the latter allowed for excellent resolution of the hydrogel microstructure. It shows globular domains with typical diameters in the range of ~10-100 nm. The hydrogel morphology has been analysed using grain size analysis as well as roughness analysis. Based on AFM topography images of hydrogel nano-domains, a set of roughness parameters has been identified which can be readily used as descriptors for spatial resolution. It includes the density of summits, Sds, the mean summit curvature, Ssc, the surface area ratio, Sdr, and the correlation length parameter, Scl37. The latter describes the length over which the autocorrelation function decays to 37% of its peak value. These parameters allow for better discrimination than the widely used root-mean-square (RMS) roughness, Sq, and are available with common image processing software packages. Systematic variation of the virtual tilt angle has indicated that these parameters are robust to small variations in plane levelling. Such image processing is frequently needed to separate the inherent surface microstructure from the global topography related to sample tilt or surface waviness. Hydrogels are an important group of biomaterials as they find numerous applications in biomedical engineering, ranging from adhesives, to controlled release of water-soluble drugs, to encapsulation of cells, to tissue engineering. Optimisation of their interactions with bioentities, such as bacteria, cells or proteins, requires accurate surface characterisation.

Munz, M.

2013-08-01

211

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

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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

2013-06-01

212

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

DEFF Research Database (Denmark)

Short-term temperature effects on photosynthesis were investigated by measuring O2 production, PSII-fluorescence kinetics, and 14C-incorporation rates in monocultures of the marine phytoplankton species Prorocentrum minimum (Pavill.) J. Schiller (Dinophyceae), Prymnesium parvum f. patelliferum ( J. C. Green, D. J. Hibberd et Pienaar) A. Larsen (Coccolithophyceae), and Phaeodactylum tricornutum Bohlin (Bacillariophyceae), grown at 15 oC and 80 umol photons m-2 s-1. Photosynthesis versus irradiance curves were measured at seven temperatures (0oC to 30oC) by all three approaches. The maximum photosynthetic rate (PCmax) was strongly stimulated by temperature, reached an optimum for Pro. minimum only (20oCâ??25oC), and showed a similar relative temperature response for the three applied methods, with Q10 ranging from 1.7 to 3.5. The maximum light utilization coefficient (alfaC) was insensitive or decreased slightly with increasing temperature. Absolute rates of O2 production were calculated from pulse-amplitude-modulated (PAM) fluorometry measurements in combination with biooptical determination of absorbed quanta in PSII. The relationship between PAM-based O2 production and measured O2 production and 14C assimilation showed a species-specific correlation, with 1.2â??3.3 times higher absolute values of PCmax and alfaC when calculated from PAM data for Pry. parvum and Ph. tricornutum but equivalent for Pro. minimum. The offset seemed to be temperature insensitive and could be explained by a lower quantum yield for O2 production than the theoretical maximum (due to Mehler-type reactions). Conclusively, the PAM technique can be used to study temperature responses of photosynthesis in microalgae when paying attention to the absorption properties in PSII.

Hancke, Kasper; Hancke, Torunn

2008-01-01

213

FKBP12.6 activates RyR1: investigating the amino acid residues critical for channel modulation.  

Science.gov (United States)

We have previously shown that FKBP12 associates with RyR2 in cardiac muscle and that it modulates RyR2 function differently to FKBP12.6. We now investigate how these proteins affect the single-channel behavior of RyR1 derived from rabbit skeletal muscle. Our results show that FKBP12.6 activates and FKBP12 inhibits RyR1. It is likely that both proteins compete for the same binding sites on RyR1 because channels that are preactivated by FKBP12.6 cannot be subsequently inhibited by FKBP12. We produced a mutant FKBP12 molecule (FKBP12E31Q/D32N/W59F) where the residues Glu(31), Asp(32), and Trp(59) were converted to the corresponding residues in FKBP12.6. With respect to the functional regulation of RyR1 and RyR2, the FKBP12E31Q/D32N/W59F mutant lost all ability to behave like FKBP12 and instead behaved like FKBP12.6. FKBP12E31Q/D32N/W59F activated RyR1 but was not capable of activating RyR2. In conclusion, FKBP12.6 activates RyR1, whereas FKBP12 activates RyR2 and this selective activator phenotype is determined within the amino acid residues Glu(31), Asp(32), and Trp(59) in FKBP12 and Gln(31), Asn(32), and Phe(59) in FKBP12.6. The opposing but different effects of FKBP12 and FKBP12.6 on RyR1 and RyR2 channel gating provide scope for diversity of regulation in different tissues. PMID:24559985

Venturi, Elisa; Galfré, Elena; O'Brien, Fiona; Pitt, Samantha J; Bellamy, Stuart; Sessions, Richard B; Sitsapesan, Rebecca

2014-02-18

214

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

215

Examination of inductance matrices and winding factors of pole-changing induction motor with pole-amplitude modulation. Pole changing from 8-pole to 6-pole by pole-amplitude modulation; PAM hoshiki kyokusu kirikae yudo dendoki no inductance gyoretsu to makisen keisu no kento. PAM hoshiki ni yotte 8 kyoku kara 6 kyoku e kirikaeru baai  

Energy Technology Data Exchange (ETDEWEB)

A pole-changing induction motor with pole-amplitude modulation (PAM) is a single-winding system, and has a unique speed ratio other than 1/2. The method of conversion from an 8-pole to a 6-pole induction motor using PAM becomes complicated compared with the method of conversion to a 10-pole motor. The present paper describes the harmonic torque prevention approach done by using the unified theory of electrical machinery for the case of 8-pole to 6-pole conversion by PAM. From the results of analysis and speed-torque experiment, it was found that this induction motor is driven by the negative-phase revolving magnetic field due to the 3rd order harmonic. It was also found that there appears 13th harmonic asynchronous torque in the motor region and 11th harmonic asynchronous torque in the braking region. Furthermore, it is shown that a long-pitch winding with a machine angle of 8/24 is recommended for the motor design in order to remove the 11th and 13th harmonic torques. 12 refs., 10 figs., 3 tabs.

Yamazaki, H.; Tsuchiya, T. [Hokkaido University, Sapporo (Japan); Anazawa, Y.; Tajima, K.; Kaga, A. [Akita University, Akita (Japan); Koido, M. [Hitachi, Ltd., Tokyo (Japan)

1994-08-20

216

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

217

Investigation of interchannel nonlinear tolerance of 256-Gb/s polarization-division multiplexing return-to-zero 16-ary quadrature amplitude modulation in a hybrid wavelength-division multiplexing transmission system using optical comb  

Science.gov (United States)

By applying recirculating frequency shifter technology to generate optical comb as neighboring channels, we have experimentally investigated the interchannel nonlinear tolerance of 256-Gbit/s polarization-division multiplexing return-to-zero 16-ary quadrature amplitude modulation (PDM-RZ-16QAM) in a co-propagation with 32-Gbaud on-off keying, binary phase-shift keying, quadrature phase-shift keying (QPSK) signals in 792-km large-area fiber transmission system. The results show that the experimental back-to-back optical signal-to-noise ratio requirement of 256-Gbit/s (32-GBaud) PDM-RZ-16QAM signal is shifted by 4.8-dB penalty in comparison with the theoretical limits. The cross-phase modulation (XPM) tolerance for 256-Gbit/s PDM-RZ-16QAM in 32-Gbaud phase-modulated neighboring channels is better than in 32-Gbaud intensity-modulated neighbors. Moreover, the performance of XPM tolerance for 256-Gbit/s PDM-RZ-16QAM in 32-Gbaud QPSK neighboring channels is the best among other kinds of modulation neighboring formats.

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

2014-01-01

218

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

Energy Technology Data Exchange (ETDEWEB)

Carbohydrate binding modules (CBMs) are specialized proteins that bind to polysaccharides and oligosaccharides. Caldanaerobius polysaccharolyticus Man5ACBM16-1/CBM16-2 bind to glucose-, mannose-, and glucose/mannose-configured substrates. The crystal structures of the two proteins represent the only examples in CBM family 16, and studies that evaluate the roles of amino acid residues in ligand binding in this family are lacking. In this study, we probed the roles of amino acids (selected based on CBM16-1/ligand co-crystal structures) on substrate binding. Two tryptophan (Trp-20 and Trp-125) and two glutamine (Gln-81 and Gln-93) residues are shown to be critical in ligand binding. Additionally, several polar residues that flank the critical residues also contribute to ligand binding. The CBM16-1 Q121E mutation increased affinity for all substrates tested, whereas the Q21G and N97R mutants exhibited decreased substrate affinity. We solved CBM/substrate co-crystal structures to elucidate the molecular basis of the increased substrate binding by CBM16-1 Q121E. The Gln-121, Gln-21, and Asn-97 residues can be manipulated to fine-tune ligand binding by the Man5A CBMs. Surprisingly, none of the eight residues investigated was absolutely conserved in CBM family 16. Thus, the critical residues in the Man5A CBMs are either not essential for substrate binding in the other members of this family or the two CBMs are evolutionarily distinct from the members available in the current protein database. Man5A is dependent on its CBMs for robust activity, and insights from this study should serve to enhance our understanding of the interdependence of its catalytic and substrate binding modules.

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

2010-11-22

219

Schematic-based 4/16/64 order quadrature amplitude modulation mapper-demapper implementation for 256 subchannel orthogonal frequency division multiplexing model on FPGA Xilinx SPARTAN 3E  

Science.gov (United States)

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique which provides higher bit rate and efficient bandwidth. This paper presents an implementation of a 4/16/64 Order Quadrature Amplitude Modulation (QAM) Mapper-Demapper for 256 Sub channel OFDM Model on Xilinx SPARTAN 3E Field-Programmable Gate Array (FPGA) series, using schematic approach. This QAMOFDM model is reconfigurable in term of its QAM order. The result shows that under the clock frequency around 262 MHz, the implementation works well, high precision is achieved at its serial output. A precision process conducted at 20 ns internal clock input period, with the 25 Mbps input bit rate requires 81.94 ?s QAM processing-time. The implementation consumes about 80 % of the total FPGA slices (3736 slices).

Imaduddin, .; Setiyanto, Budi; Litasari, .

2010-03-01

220

Higher rank cylinder amplitude  

International Nuclear Information System (INIS)

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

1980-01-01

 
 
 
 
221

Numerical modeling of tides in the Great Bay Estuarine System: dynamical balance and spring-neap residual modulation  

Science.gov (United States)

The Great Bay Estuarine System, in New Hampshire, USA, has been the focus area for an attempt to develop a robust finite element method model for estuarine hydrodynamics. Past studies used a nonlinear, time stepping, kinematic model with limited success (Ip et al. Advances in fluid mechanics III, WIT, Southampton (2000) 569; Bilgili et al. J. Geophys. Res. - Oceans 107 (2002); Ertürk et al. Estuar. Coast. Shelf Sci. 47 (1998) 119). We add dynamic physics (that is, local accelerations) for deep-water areas and keep kinematic physics (that is, without local and advective accelerations), with the inclusion of a porous medium beneath the open channel, for shallow and dewatering areas. The choice of which physics set to apply is made on an elemental depth dependent basis. The addition of the local acceleration terms for deep-water areas is seen to greatly improve accuracy in matching of tidal phasing over previous studies. Simulations involving M 2/M 4/M 6 tidal constituents result in strong agreement to observed data from the 1975 Great Bay field program (Swift & Brown, Estuar. Coast. Shelf Sci. 17 (1983) 297), in terms of both tidal heights and cross-section averaged velocities. Comparisons with 10 tidal elevation observation stations and four cross-section averaged current transects show good agreement, displaying average normalized root mean square misfit values of 0.08 and 0.25, respectively. Study of the simulated momentum balance shows the size of the contributions from acceleration terms to be on the order of a third the size of the contributions from the pressure gradient and bottom stress terms. Although relatively small, they are observed to peak at the crucial time of tidal reversal. Application of the model for long-term simulation using an M 2/N 2/S 2 forcing shows the ability to realistically capture the spring-neap cycle. The tidally rectified flow is generally described as a constant spatial pattern with overall amplitude modulation following the spring-neap cycle.

McLaughlin, J. W.; Bilgili, A.; Lynch, D. R.

2003-05-01

222

SAR impulse response with residual chirps.  

Energy Technology Data Exchange (ETDEWEB)

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

Doerry, Armin Walter

2009-06-01

223

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

224

Contribution of extracellular negatively charged residues to ATP action and zinc modulation of rat P2X2 receptors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two histidines are known to be essential for zinc potentiation of rat P2X2 receptors, but the chemistry of zinc coordination would suggest that other residues also participate in this zinc binding site. There is also a second lower affinity zinc binding site in P2X2 receptors whose constituents are unknown. To assess whether extracellular acidic residues of the P2X2 receptor contribute to zinc potentiation or inhibition, site-directed mutagenesis was used to produce alanine substitutions at e...

Friday, Sean C.; Hume, Richard I.

2008-01-01

225

Superlinear Amplitude Amplification  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quantum search/amplitude amplification algorithms are designed to be able to amplify the amplitude in the target state linearly with the number of operations. Since the probability is the square of the amplitude, this results in the success probability rising quadratically with the number of operations. This paper presents a new kind of quantum search algorithm in which the amplitude of the target state, itself increases quadratically with the number of operations. However, ...

Grover, Lov K.

2008-01-01

226

Construction of diffractive amplitudes  

International Nuclear Information System (INIS)

Starting from a simple parametrization of production amplitudes an explicit construction of the diffractive elastic amplitude through multiparticle unitarity is given. It is shown that the phase cancellation effect is essential in order to obtain an elastic amplitude which displays a diffractive peak in qualitative agreement with the data. (orig.)

1983-09-01

227

Experimental study on MOSFET pulse modulator  

International Nuclear Information System (INIS)

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

2006-09-01

228

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

Directory of Open Access Journals (Sweden)

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

A.O. Oso

2011-01-01

229

Algebras for Amplitudes  

CERN Multimedia

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

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

2012-01-01

230

DYRK1A Autophosphorylation on Serine Residue 520 Modulates Its Kinase Activity via 14-3-3 Binding  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dual-specificity tyrosine-phosphorylated and regulated kinase (DYRK) proteins are an evolutionarily conserved family of protein kinases, with members identified from yeast to humans, that participate in a variety of cellular processes. DYRKs are serine/threonine protein kinases that are activated by autophosphorylation on a tyrosine residue in the activation loop. The family member DYRK1A has been shown to phosphorylate several cytosolic proteins and a number of splicing and transcription fac...

Alvarez, Mo?nica; Altafaj, Xavier; Aranda, Sergi; La Luna, Susana

2007-01-01

231

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.  

Science.gov (United States)

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. PMID:15066178

Weyer, Kathrin; Overgaard, Michael T; Laursen, Lisbeth S; Nielsen, Claus G; Schmitz, Alexander; Christiansen, Michael; Sottrup-Jensen, Lars; Giudice, Linda C; Oxvig, Claus

2004-04-01

232

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

International Nuclear Information System (INIS)

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

2000-12-11

233

DFB laser with attached external intensity modulator  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a theoretical study of the frequency pulling effect exerted on a DFB laser by an external amplitude modulator that is directly attached to it. The modulator consists of a piece of waveguide whose loss is modulated by means of an externally applied voltage. The modulator affects the laser due to residual reflections from its far end which appear as a variable effective reflectivity to the output end of the DFB laser. Modulation affects the magnitude as well as the phase of the effective reflection coefficient presented to the laser due to the coupling of the real and imaginary parts of the effective refractive index of the modulator waveguide. The tuning problem is formulated as an eigenvalue equation for the DFB laser in the presence of an externally attached lossy cavity.

Marcuse, D. (AT and T Bell Labs. Holmdel, NJ (US))

1990-02-01

234

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

DEFF Research Database (Denmark)

One industrial process for the production of cellulosic ethanol and or value-added products involves exposing the cellulose content of plant materials by steam explosion in the presence of strong acid, followed by its neutralization and subsequent digestion with a cocktail of cellulolytic enzymes. These enzymes typically have activity optima at slightly acidic or neutral pH and so generating enzymes that are more active and tolerant in more acidic conditions would help to reduce associated costs. Here, we describe the engineering of cellulase A from Cellulomonas fimi as a model to replace residues that were identified as potentially influencing the pH-activity profile of the enzyme based on sequence alignments and analysis of the known three-dimensional structures of other CAZy family 6 glycoside hydrolases with the aim to lower its pH optimum. Twelve specific residues and a sequence of eight were identified and a total of 30 mutant enzymes were generated. In addition to being replaced with natural amino acids, some of the identified residues were substituted with cysteine and subsequently oxidized to cysteinesulfinate. Of the four single amino acid replacements that produced enhancements of activity at acidic pH, three involved the removal of charged groups from the surface of the enzyme. The generation of double mutations provided mixed results but the combination of Glu407â??Ala and Tyr321â??Phe replacements had an additive effect on the enhancement, reaching a total activity that was 162 of the wild-type level. This study thus illustrated the utility of altering the surface charge properties of the family 6 glycoside hydrolases to enhance activity at low pH and thereby an avenue for further protein engineering. © 2011 The Author Published by Oxford University Press. All rights reserved.

Cockburn, Darrell W.; Clarke, Anthony J.

2011-01-01

235

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2010-01-01

236

Calculating scattering amplitudes efficiently  

International Nuclear Information System (INIS)

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

1995-06-04

237

Immunogenicity of membrane-bound HIV-1 gp41 membrane-proximal external region (MPER) segments is dominated by residue accessibility and modulated by stereochemistry.  

Science.gov (United States)

Structural characterization of epitope-paratope pairs has contributed to the understanding of antigenicity. By contrast, few structural studies relate to immunogenicity, the process of antigen-induced immune responses in vivo. Using a lipid-arrayed membrane-proximal external region (MPER) of HIV-1 glycoprotein 41 as a model antigen, we investigated the influence of physicochemical properties on immunogenicity in relation to structural modifications of MPER/liposome vaccines. Anchoring the MPER to the membrane via an alkyl tail or transmembrane domain retained the MPER on liposomes in vivo, while preserving MPER secondary structure. However, structural modifications that affected MPER membrane orientation and antigenic residue accessibility strongly impacted induced antibody responses. The solvent-exposed MPER tryptophan residue (Trp-680) was immunodominant, focusing immune responses, despite sequence variability elsewhere. Nonetheless, immunogenicity could be readily manipulated using site-directed mutagenesis or structural constraints to modulate amino acid surface display. These studies provide fundamental insights for immunogen design aimed at targeting B cell antibody responses. PMID:24047898

Kim, Mikyung; Song, Likai; Moon, James; Sun, Zhen-Yu J; Bershteyn, Anna; Hanson, Melissa; Cain, Derek; Goka, Selasie; Kelsoe, Garnett; Wagner, Gerhard; Irvine, Darrell; Reinherz, Ellis L

2013-11-01

238

Nullification of threshold amplitudes  

International Nuclear Information System (INIS)

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

2002-11-15

239

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

240

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.

Zengliang Yu

2003-09-01

 
 
 
 
241

Individual substitutions of clustered arginine residues of the sensor kinase KdpD of Escherichia coli modulate the ratio of kinase to phosphatase activity.  

Science.gov (United States)

Escherichia coli responds to K+ limitation or high osmolarity by induction of the kdpFABC operon coding for the high affinity K+-translocating Kdp-ATPase. KdpD, the sensor kinase of this system, is a bifunctional enzyme catalyzing the autophosphorylation by ATP and the dephosphorylation of the corresponding response regulator KdpE. Here we demonstrate that individual replacements of clustered arginine residues located close to transmembrane domain TM4 modulate the ratio of kinase to phosphatase activity. Thus KdpD-Arg511 --> Gln is characterized by an increase in the kinase activity and a loss of the phosphatase activity. However, when Arg at position 511 is replaced with Lys, activities of the corresponding protein are comparable with wild-type KdpD. In contrast, replacement of arginine residues at positions 503, 506, or 508 with glutamine or lysine causes a decrease of the kinase and an increase of the phosphatase activities. Changes of the activities of these KdpD proteins correspond with alterations in kdpFABC expression. Thus KdpD-Arg511 --> Gln causes constitutive expression of kdpFABC. KdpD proteins with Arg replacements at positions 503, 506, or 508 are unable to respond to osmolarity, whereas the sensing of K+ limitation is not influenced. Simultaneous replacement of arginine residues 508 and 511 or 506, 508, and 511 with glutamine leads to a decrease of the phosphatase activity. However, kdpFABC expression is dependent on K+ and osmolarity. Finally, when Arg513 is replaced with glutamine the amount of KdpD detected in the membrane is drastically reduced. These results imply that there is an equilibrium between the kinase and phosphatase activities of KdpD, which can be shifted by the replacement of one arginine residue. An electrostatic switch mechanism within the protein is proposed through which the ratio of kinase to phosphatase is regulated. Finally, these results lend support to the notion that KdpD can be activated by two distinct stimuli, K+ limitation and osmolarity. PMID:9756874

Jung, K; Altendorf, K

1998-10-01

242

Large amplitude electromagnetic waves  

International Nuclear Information System (INIS)

Large amplitude electromagnetic waves have been studied in connection with several astrophysical problems. It has been quite successful in the interpretation of the slowing-down of pulsars as due to the emission of large amplitude, low frequency electromagnetic waves. With this interpretation the necessity has emerged to consider exact solutions of the self-consistent fluid and Maxwell equations to describe these nonlinear electromagnetic waves. Radiative damping of large amplitude waves, as well as the Weibel instability are finally discussed. 36 refs, 8 figs, 4 tabs

1984-01-01

243

CAMAC nonius amplitude-to-digital convereter  

International Nuclear Information System (INIS)

Spectrometric amplitude-to-digital converter is designed for measuring voltages within the 0-2.5 V range with automatic substraction of linear gate base. The conversion time is 1 mus. The differential nonlinearity is <20%. The discharge number is 10 plus overcharging discharge. The module contains a buffer with the 1Kx11 capacity

1990-01-01

244

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-04-30

245

BK channel activation by tungstate requires the ?1 subunit extracellular loop residues essential to modulate voltage sensor function and channel gating.  

Science.gov (United States)

Tungstate, a compound with antidiabetic, antiobesity, and antihypertensive properties, activates the large-conductance voltage- and Ca(2+)-dependent K(+) (BK) channel containing either ?1 or ?4 subunits. The BK activation by tungstate is Mg(2+)-dependent and promotes arterial vasodilation, but only in precontracted mouse arteries expressing ?1. In this study, we further explored how the ?1 subunit participates in tungstate activation of BK channels. Activation of heterologously expressed human BK??1 channels in inside-out patches is fully dependent on the Mg(2+) sensitivity of the BK ? channel subunit even at high (10 ?M) cytosolic Ca(2+) concentration. Alanine mutagenesis of ?1 extracellular residues Y74 or S104, which destabilize the active voltage sensor, greatly decreased the tungstate-induced left-shift of the BK??1 G-V curves in either the absence or presence of physiologically relevant cytosolic Ca(2+) levels (10 ?M). The weakened tungstate activation of the BK??1Y74A and BK??1S104A mutant channels was not related to decreased Mg(2+) sensitivity. These results, together with previously published reports, support the idea that the putative binding site for tungstate-mediated BK channel activation is located in the pore-forming ? channel subunit, around the Mg(2+) binding site. The role of ?1 in tungstate-induced channel activation seems to rely on its interaction with the BK ? subunit to modulate channel activity. Loop residues that are essential for the regulation of voltage sensor activation and gating of the BK channel are also relevant for BK activation by tungstate. PMID:24158430

Fernández-Mariño, Ana I; Valverde, Miguel A; Fernández-Fernández, José M

2014-07-01

246

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

247

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

248

Radar Ambiguity Function for Random Intrapulse-Modulated Radar Signals.  

Science.gov (United States)

The radar ambiguity function for random intrapulse-modulated signals with constant frequency and amplitude for each sub-pulse was considered. The amplitude and frequency of each sub-pulse were random variables. The amplitude modulation (AM) and frequency ...

H. N. Hebert

1974-01-01

249

Pulse amplitude analyser circuits  

International Nuclear Information System (INIS)

A pulse amplitude analyser circuit having a very short dead-time comprises a plurality of amplitude discriminators having a common input and progressively increasing threshold levels, and a plurality of pulse storage elements for receiving the respective discriminator outputs, other than that of the discriminator which has the lowest threshold level. Pulse gates operate in conjuction with pulse storage elements and with a further such element which receives the output of the discriminator, to detect the back edge of the output pulse from the discriminator having the highest exceeded threshold level, indicating a fall below that level, and thereupon to restore the pulse storage elements to an initial condition. (author)

1984-03-23

250

Stability in Period and Amplitude: The High-Amplitude ? Scuti Star YZ Boötis  

Science.gov (United States)

The variability of period and amplitude of the high-amplitude ? Scuti star YZ Boo was thoroughly investigated based on a comprehensive analysis of new time-series photometry and other available data. Fourier analysis, O Cdiagram, and wavelet analysis establish a clear picture for the star's time-dependent behavior in period and amplitude. We detected no additional frequencies being intrinsic to the variable or caused by amplitude/frequency modulation confirming its mono-periodicity. We reveal the pulsation of YZ Boo is quite stable in both period and amplitude over the past 50 years. Short-term variations at cycle level including “anomalous cycles” are present clearly, while long-term variations in period and amplitude at annual base are insignificant. However, we note an increment from 2000 to 2003 in both period and amplitude. In 2000 the amplitude reached the lowest. This is indicated by the Fourier and wavelet results. In the long term, O Cfits and wavelet analysis agree with the Fourier results that the period change of YZ Boo is still inconclusive.

Zhou, Ai-Ying

2006-01-01

251

Light Meson Distribution Amplitudes  

CERN Document Server

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

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

2010-01-01

252

Universal boundary reflection amplitudes  

CERN Multimedia

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

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

2003-01-01

253

Fusing gauge theory tree amplitudes into loop amplitudes  

International Nuclear Information System (INIS)

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

1995-02-06

254

Universal boundary reflection amplitudes  

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-03-29

255

N=4 Scattering Amplitudes and the Deformed Grassmannian  

CERN Document Server

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

Ferro, Livia; Staudacher, Matthias

2014-01-01

256

Closed String Amplitudes as Single-Valued Open String Amplitudes  

CERN Document Server

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

Stieberger, Stephan

2014-01-01

257

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

CERN Document Server

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

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

2011-01-01

258

On the adelic string amplitudes  

International Nuclear Information System (INIS)

Some remarkable properties of the adelic string amplitudes for the physical domain of the Mandelstam variables are considered. It is shown that the p-adic four-point functions are always negative. Also, a formula is obtained which expresses the product of moduli of the p-adic amplitudes and the Veneziano amplitude in terms of the zeta functions. This product is absolutely convergent unlike the divergent product of these amplitudes without moduli, recently considered by Freund and Witten. Using the zeta function representation, p-adic interpolation of the Veneziano amplitude is also considered. (orig.)

1988-08-11

259

On the adelic string amplitudes  

Energy Technology Data Exchange (ETDEWEB)

Some remarkable properties of the adelic string amplitudes for the physical domain of the Mandelstam variables are considered. It is shown that the p-adic four-point functions are always negative. Also, a formula is obtained which expresses the product of moduli of the p-adic amplitudes and the Veneziano amplitude in terms of the zeta functions. This product is absolutely convergent unlike the divergent product of these amplitudes without moduli, recently considered by Freund and Witten. Using the zeta function representation, p-adic interpolation of the Veneziano amplitude is also considered.

Aref' eva, I.Ya.; Volovich, I.V.; Dragovic, B.G.

1988-08-11

260

Finite amplitude method for the RPA solution  

CERN Multimedia

We propose a practical method to solve the random-phase approximation (RPA) in the self-consistent Hartree-Fock (HF) and density-functional theory. The method is based on numerical evaluation of the residual interactions utilizing finite amplitude of single-particle wave functions. The method only requires calculations of the single-particle Hamiltonian constructed with independent bra and ket states. Using the present method, the RPA calculation becomes possible with a little extension of a numerical code of the static HF calculation. We demonstrate usefulness and accuracy of the present method performing test calculations for isoscalar responses in deformed 20Ne.

Nakatsukasa, Takashi; Yabana, Kazuhiro

2007-01-01

 
 
 
 
261

Generator of Stable Amplitude Spectroscopy Pulses  

CERN Document Server

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

262

Generator of stable amplitude spectroscopy pulses  

International Nuclear Information System (INIS)

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

2004-01-01

263

Large Amplitude Oscillations in Prominences  

CERN Document Server

Since the first reports of oscillations in prominences in 1930s there have been major theoretical and observational advances to understand the nature of these oscillatory phenomena leading to a whole new field of so called "prominence seismology". There are two types of oscillatory phenomena observed in prominences; "small amplitude oscillations" (~2-3 km s$^{-1}$) which are quite common and "large amplitude oscillations" ($>$20 km s$^{-1}$) for which observations are scarce. Large amplitude oscillations have been found as "winking filament" in H$\\alpha$ as well as motion in the sky plane in H$\\alpha$, EUV, micro-wave and He 10830 observations. Historically, it was suggested that the large amplitude oscillations in prominences were triggered by disturbances such as fast-mode MHD waves (Moreton wave) produced by remote flares. Recent observations show, in addition, that near-by flares or jets can also create such large amplitude oscillations in prominences. Large amplitude oscillations, which are observed both...

Tripathi, D; Jain, R

2009-01-01

264

On the Period-Amplitude and Amplitude-Period Relationships  

Science.gov (United States)

Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.

Wilson, Robert M.; Hathaway, David H.

2008-01-01

265

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

266

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

International Nuclear Information System (INIS)

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

1984-05-03

267

Identification and Modulation of the Key Amino Acid Residue Responsible for the pH Sensitivity of Neoculin, a Taste-Modifying Protein  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Neoculin occurring in the tropical fruit of Curculigo latifolia is currently the only protein that possesses both a sweet taste and a taste-modifying activity of converting sourness into sweetness. Structurally, this protein is a heterodimer consisting of a neoculin acidic subunit (NAS) and a neoculin basic subunit (NBS). Recently, we found that a neoculin variant in which all five histidine residues are replaced with alanine elicits intense sweetness at both neutral and acidic pH but has no ...

Nakajima, Ken-ichiro; Yokoyama, Kanako; Koizumi, Taichi; Koizumi, Ayako; Asakura, Tomiko; Terada, Tohru; Masuda, Katsuyoshi; Ito, Keisuke; Shimizu-ibuka, Akiko; Misaka, Takumi; Abe, Keiko

2011-01-01

268

Approximating chiral SU(3) amplitudes  

CERN Document Server

We construct large-N_c motivated approximate chiral SU(3) amplitudes of next-to-next-to-leading order. The amplitudes are independent of the renormalization scale. Fitting lattice data with those amplitudes allows for the extraction of chiral coupling constants with the correct scale dependence. The differences between approximate and full amplitudes are required to be at most of the order of N^3LO contributions numerically. Applying the approximate expressions to recent lattice data for meson decay constants, we determine several chiral couplings with good precision. In particular, we obtain a value for F_0, the meson decay constant in the chiral SU(3) limit, that is more precise than all presently available determinations.

Ecker, G; Neufeld, H

2013-01-01

269

Ultrasoft amplitudes in hot QCD  

International Nuclear Information System (INIS)

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

2000-03-20

270

Scattering amplitudes in gauge theories  

CERN Multimedia

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

Henn, Johannes M

2014-01-01

271

Amplitude-mediated chimera states.  

Science.gov (United States)

We investigate the possibility of obtaining chimera state solutions of the nonlocal complex Ginzburg-Landau equation (NLCGLE) in the strong coupling limit when it is important to retain amplitude variations. Our numerical studies reveal the existence of a variety of amplitude-mediated chimera states (including stationary and nonstationary two-cluster chimera states) that display intermittent emergence and decay of amplitude dips in their phase incoherent regions. The existence regions of the single-cluster chimera state and both types of two-cluster chimera states are mapped numerically in the parameter space of C(1) and C(2), the linear and nonlinear dispersion coefficients, respectively, of the NLCGLE. They represent a new domain of dynamical behavior in the well-explored rich phase diagram of this system. The amplitude-mediated chimera states may find useful applications in understanding spatiotemporal patterns found in fluid flow experiments and other strongly coupled systems. PMID:24229259

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

2013-10-01

272

Approximating chiral SU(3) amplitudes  

Energy Technology Data Exchange (ETDEWEB)

We construct large-N{sub c} motivated approximate chiral SU(3) amplitudes of next-to-next-to-leading order. The amplitudes are independent of the renormalisation scale. Fitting lattice data with those amplitudes allows for the extraction of chiral coupling constants with the correct scale dependence. The differences between approximate and full amplitudes are required to be at most of the order of N{sup 3}LO contributions numerically. Applying the approximate expressions to recent lattice data for meson decay constants, we determine several chiral couplings with good precision. In particular, we obtain a value for F{sub 0}, the meson decay constant in the chiral SU(3) limit, that is more precise than all presently available determinations. (orig.)

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

2014-02-15

273

Scattering amplitudes in Lifshitz spacetime  

CERN Document Server

We consider the calculation of scattering amplitudes in field theories dual to Lifshitz spacetimes. These amplitudes provide an interesting probe of the IR structure of the field theory; our aim is to use them to explore the observable consequences of the singularity in the spacetime. We assume the amplitudes can be related by T-duality to a Wilson loop, as in the AdS case, and determine the bulk minimal surfaces for the simplest cusp Wilson loop. We use this to determine the leading IR singularity in the amplitude. We find there is a stronger IR singularity for z >1 than for z=1, with a coefficient which vanishes as z goes to 1.

Andrade, Tomas; Ross, Simon F

2014-01-01

274

Frequency, phase, and amplitude changes of the hydrogen maser oscillation  

Science.gov (United States)

The frequency, the phase, and the amplitude changes of the hydrogen maser oscillation, which are induced by the modulation of the cavity resonant frequency, are considered. The results obtained apply specifically to one of the H-maser cavity autotuning methods which is actually implemented, namely the cavity frequency-switching method. The frequency, the phase, and the amplitude changes are analyzed theoretically. The phase and the amplitude variations are measured experimentally. It is shown, in particular, that the phase of oscillation is subjected to abrupt jumps at the times of the cavity frequency switching, whose magnitude is specified. The results given can be used for the design of a phase-locked loop (PLL) aimed at minimizing the transfer of the phase modulation to the slaved VCXO.

Audoin, Claude; Diener, William A.

1992-01-01

275

Amplitude death state for hearing  

CERN Multimedia

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

276

Interpolating Axial Anomaly Induced Amplitudes  

CERN Multimedia

We propose an interpolating formula for the amplitude induced by the axial anomaly, concentrating on the $\\pi^0\\gamma^{\\ast}\\gamma^{\\ast}$ transition form factor. The QCD corrections to this amplitude are generally described by two major contributions coming from the $q\\bar{q}$ bound state and the background continuous spectrum, respectively. For the first contribution, we include the lowest vector bound state using the realization of the dynamical gauge boson of hidden local symmetry. The second contribution is included as the triangle quark loop in which a constituent mass is adopted as a internal quark mass and the amplitudes are smeared out around the threshold. Using the resulting form factor, we fit the experimental data for the $\\pi^0\\gamma$ and the $\\omega\\pi^0$ transition form factors and show that our result describes the experimental data well.

Bando, M; Bando, Masako; Harada, Masayasu

1994-01-01

277

Nonsinglet pentagons and NHMV amplitudes  

CERN Document Server

Scattering amplitudes in maximally supersymmetric gauge theory receive a dual description in terms of the expectation value of the super Wilson loop stretched on a null polygonal contour. This makes the analysis amenable to nonperturbative techniques. Presently, we elaborate on a refined form of the operator product expansion in terms of pentagon transitions to compute twist-two contributions to NMHV amplitudes. To start with, we provide a novel derivation of scattering matrices starting from Baxter equations for flux-tube excitations propagating on magnon background. We propose bootstrap equations obeyed by pentagon form factors with nonsinglet quantum numbers with respected to the R-symmetry group and provide solutions to them to all orders in 't Hooft coupling. These are then successfully confronted against available low-loop perturbative calculations for NMHV amplitudes.

Belitsky, A V

2014-01-01

278

Cavity enhanced terahertz modulation  

Science.gov (United States)

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

Born, N.; Scheller, M.; Koch, M.; Moloney, J. V.

2014-03-01

279

All-digital QPSK modulator  

Science.gov (United States)

Circuit consisting to only four components (2 IC chips and 2 time delay devices) modulates RF signal with 2 asynchronous digital data signals. Digital modulator is virtually free of amplitude modulation, is not subject to temperature effects from other components, dissipates less power, and is far simpler than its analog predecessors.

Burgess, R. W.; Julian, R. L.

1980-01-01

280

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

Science.gov (United States)

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

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

2014-01-01

 
 
 
 
281

Solid residues  

International Nuclear Information System (INIS)

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

1995-01-01

282

Distribution Amplitudes of Pseudoscalar Mesons  

CERN Multimedia

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.

Braun, V M; Horsley, R; Perlt, H; Pleiter, D; Rakow, P E L; Schierholz, G; Schiller, A; Schroers, W; Stüben, H; Zanotti, J M

2006-01-01

283

Amplitude alignment for preshower detector  

CERN Document Server

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

284

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

285

Distribution amplitudes of vector mesons  

International Nuclear Information System (INIS)

Results are presented for the lowest moment of the distribution amplitude for the K* 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.)

2007-08-04

286

Scattering amplitudes in gauge theories  

International Nuclear Information System (INIS)

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

2014-01-01

287

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

288

Discontinuity formulas for multiparticle amplitudes  

International Nuclear Information System (INIS)

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 condition. The discontinuity formulas to be derived are the basis of multi-particle fixed-t dispersion relations

1976-01-01

289

Scattering amplitudes in gauge theories  

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-03-01

290

Two- and three-loop amplitudes in the bosonic string theory  

International Nuclear Information System (INIS)

Explicit formulae are obtained for two- and three-loop vacuum amplitudes in the theory of closed oriented bosonic strings at ?=26 in terms of the theta-constants, with the module space being parametrized by period matrices

1986-01-01

291

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

LENUS (Irish Health Repository)

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

Adamson, Justus

2012-02-01

292

Effect of Modulation Error on All Optical Fiber Current Transformers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For actively modulated In-line Sagnac interferential all optic fiber current transformers (AOFCTs), the accuracies are directly affected by the amplitude of the modulation signal. In order to deeply undertand the function of the modulator, a theoretical model of modulation effect to AOFCTs is built up in this paper. The effect of the amplitude of the modulation signal to the output intensity of AOFCTs is theoretically formulated and numerical calculated. The results show that the modulation v...

Zhengping Wang; Yuekun Wang; Shuai Sun

2012-01-01

293

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

294

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

295

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

296

Infrared singularities in QCD amplitudes  

CERN Multimedia

We review recent progress in determining the infrared singularity structure of on-shell scattering amplitudes in massless gauge theories. We present a simple ansatz where soft singularities of any scattering amplitude of massless partons, to any loop order, are written as a sum over colour dipoles, governed by the cusp anomalous dimension. We explain how this formula was obtained, as the simplest solution to a newly-derived set of equations constraining the singularity structure to all orders. We emphasize the physical ideas underlying this derivation: the factorization of soft and collinear modes, the special properties of soft gluon interactions, and the notion of the cusp anomaly. Finally, we briefly discuss potential multi-loop contributions going beyond the sum-over-dipoles formula, which cannot be excluded at present.

Gardi, Einan

2009-01-01

297

Method and apparatus for correcting amplitude variation in electro-optic laser systems  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a method of correcting the amplitude variation induced by electro-optic crystal birefringence within a laser system. It comprises: actuating a laser gain medium being disposed within a resonant cavity defined by an end reflector and a partially reflective outcoupler; frequency modulating the laser light by passing the light through an electro-optic crystal modulator disposed within the resonant cavity, the modulator being activated by a time varying electrical signal, wherein crystal birefringence in the electro-optic crystal modulator causes elliptical polarization in the linearly polarized light and amplitude variation in the frequency modulated laser light; and correcting the amplitude variation by changing the elliptically polarized light to a linear polarization within the resonant cavity.

Chien, K.R.; Reeder, R.A.; Stovall, H.D.

1991-05-21

298

Nonlinear graphene plasmonics: amplitude equation  

CERN Multimedia

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

299

An automatic amplitude control algorithm  

Energy Technology Data Exchange (ETDEWEB)

A computational scheme for a TARA algorithm is proposed; this scheme increases the operational productivity by decreasing the number of division operations and as a result of the efficient use of the computer's special processor and processor. The advantages and drawbacks of the computational scheme are discussed; this scheme is based on a peak-to-peak evaluation of the amplitude envelope of the seismic recordings.

Kaplan, S.A.; Afanaseva, L.A.; Diudikova, S.K.; Romanova, S.A.

1981-01-01

300

The Amplitude of Mass Fluctuations  

CERN Document Server

We determine the linear amplitude of mass fluctuations in the universe, sigma_8, from the abundance of massive clusters at redshifts z=0.5-0.8. The evolution of massive clusters depends exponentially on the amplitude of mass fluctuations and thus provides a powerful measure of this important cosmological parameter. The relatively high abundance of massive clusters observed at z>0.5, and the relatively slow evolution of their abundance with time, suggest a high amplitude of mass fluctuations: sigma_8=0.9 +-10% for Omega_m=0.4, increasing slightly to sigma_8=0.95 for Omega_m=0.25 and sigma_8=1.0 for Omega_m=0.1 (flat CDM models). We use the cluster abundance observed at z=0.5-0.8 to derive a normalization relation from the high-redshift clusters, which is only weakly dependent on Omega_m: sigma_8*Omega_m^{0.14}=0.78 +-0.08. When combined with recent constraints from the present-day cluster mass function, sigma_8*Omega_m^{0.6}=0.33 +-0.03, we find sigma_8=0.98 +-0.1 and Omega_m=0.17 +-0.05. Low sigma_8 values (&...

Bahcall, Neta A; Bahcall, Neta A.; Bode, Paul

2003-01-01

 
 
 
 
301

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

302

Fusion residues  

International Nuclear Information System (INIS)

This paper discusses when and how the Verlinde dimensions of a rational conformal field theory can be expressed as correlation functions in a topical LG theory. It is seen that a necessary condition is that the RCFT fusion rules must exhibit an extra symmetry. The authors consider two particular perturbations of the Grassmannian superpotentials. The topological LG residues in one perturbation, introduced by Gepner, are shown to be a twisted version of the SU(N)k Verlinde dimensions. The residues in the other perturbations are the twisted Verlinde dimensions of another RCFT; these topological LG correlation functions are conjectured to be the correlation functions of the corresponding Grassmannian topological sigma model with a coupling in the action to instanton number

1991-12-14

303

Fusion residues  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses when and how the Verlinde dimensions of a rational conformal field theory can be expressed as correlation functions in a topical LG theory. It is seen that a necessary condition is that the RCFT fusion rules must exhibit an extra symmetry. The authors consider two particular perturbations of the Grassmannian superpotentials. The topological LG residues in one perturbation, introduced by Gepner, are shown to be a twisted version of the SU(N){sub k} Verlinde dimensions. The residues in the other perturbations are the twisted Verlinde dimensions of another RCFT; these topological LG correlation functions are conjectured to be the correlation functions of the corresponding Grassmannian topological sigma model with a coupling in the action to instanton number.

Intriligator, K. (Lyman Lab. of Physics, Harvard Univ., Cambridge, MA (US))

1991-12-14

304

Full phase and amplitude control in computer-generated holography.  

Science.gov (United States)

We report what we believe to be the first realization of a computer-generated complex-valued hologram recorded in a single film of photoactive polymer. Complex-valued holograms give rise to a diffracted optical field with control over its amplitude and phase. The holograms are generated by a one-step direct laser writing process in which a spatial light modulator (SLM) is imaged onto a polymer film. Temporal modulation of the SLM during exposure controls both the strength of the induced birefringence and the orientation of the fast axis. We demonstrate that complex holograms can be used to impart arbitrary amplitude and phase profiles onto a beam and thereby open new possibilities in the control of optical beams. PMID:19953153

Fratz, Markus; Fischer, Peer; Giel, Dominik M

2009-12-01

305

Full phase and amplitude control in computer generated holography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report what we believe to be the first realization of a computer-generated complex-valued hologram recorded in a single film of photoactive polymer. Complex-valued holograms give rise to a diffracted optical field with control over its amplitude and phase. The holograms are generated by a one-step direct laser writing process in which a spatial light modulator (SLM) is imaged onto a polymer film. Temporal modulation of the SLM during exposure controls both the strength of the induced biref...

Fratz, M.; Fischer, P.; Giel, D. M.

2009-01-01

306

Response accuracy rating modulates ERN and Pe amplitudes.  

Science.gov (United States)

Response accuracy ratings are often used in studies investigating the relationship between ERP correlates of performance monitoring and error awareness. Still, it is unclear whether the act of rating response correctness changes ERP correlates of performance monitoring. In order to investigate the influence of response accuracy ratings, a flanker task was conducted with or without concomitant accuracy rating and ERPs were compared between the two conditions. Error- and correct-related negativities were increased in the rating condition, possibly indicating an increase in performance monitoring. The error positivity differed more strongly between errors and correct responses in the rating condition. Additionally, correct reaction times were slower and post-error slowing was diminished in the rating condition, pointing toward a more cautious response strategy. These possible confounds should be taken into account by future studies using response accuracy ratings. PMID:24184812

Grützmann, Rosa; Endrass, Tanja; Klawohn, Julia; Kathmann, Norbert

2014-02-01

307

Complete determination of reaction amplitudes  

Energy Technology Data Exchange (ETDEWEB)

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

Ramachandran, G.; Sandhya, S.N.

1988-09-01

308

One loop amplitudes in ABJM  

Science.gov (United States)

For three dimensional {N} = 6 superconformal field theories we compute oneloop scattering amplitudes for any number of external particles. We focus on a particular subsector of {N} = 2 invariant superamplitudes for which the ordinary perturbative evaluation becomes very easy. The result we obtain is in general non-vanishing. For six external particles our findings are sufficient for determining the complete expression of the {N} = 6 superamplitude at this order. We discuss the symmetries of the result and its anomalous variation under superconformal generators.

Bianchi, Marco S.; Leoni, Matias; Mauri, Andrea; Penati, Silvia; Santambrogio, Alberto

2012-07-01

309

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

310

Superstring amplitudes and contact interactions  

International Nuclear Information System (INIS)

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

1987-01-01

311

Constructing Amplitudes from Their Soft Limits  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-12-09

312

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

313

Amplitude control of quantum interference  

CERN Multimedia

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

Mullin, W J

2011-01-01

314

Completeness of the scattering amplitudes  

CERN Multimedia

Let $f\\in L^2(S^2)$ be an arbitrary fixed function on the unit sphere $S^2$, and $D\\subset \\R^3$ be an arbitrary fixed bounded domain. Let $k>0$ and $\\alpha\\in S^2$ be fixed. It is proved that there exists a potential $q\\in L^2(D)$ such that the corresponding scattering amplitude $A(\\alpha')=A_q(\\alpha')=A_q(\\alpha',\\alpha,k)$ approximates $f(\\alpha')$ with arbitrary high accuracy: $\\|f(\\alpha')-A_q(\\alpha')_{L^2(S^2)}\\|\\leq\\ve$ where $\\ve>0$ is an arbitrarily small fixed number. This means that the set $\\{A_q(\\alpha')\\}_{\\forall q\\in L^2(D)}$ is complete in $L^2(S^2)$. The results can be used for constructing nanotechnologically "smart materials".

Ramm, A G

2006-01-01

315

Residual shear deformations in the coronary artery.  

Science.gov (United States)

Quantifying arterial residual deformations is critical for understanding the stresses and strains within the arterial wall during physiological and pathophysiological conditions. This study presents novel findings on residual shear deformations in the left anterior descending coronary artery. Residual shear deformations are most evident when thin, long axial strips are cut from the artery. These strips deform into helical configurations when placed in isotonic solution. A residual shear angle is introduced as a parameter to quantify the residual shear deformations. Furthermore, a stress analysis is performed to study the effects of residual shear deformations on the intramural shear stress distribution of an artery subjected to pressure, axial stretch, and torsion using numerical simulation. The results from the stress analyses suggest that residual shear deformations can significantly modulate the intramural shear stress across the arterial wall. PMID:24686990

Wang, Ruoya; Gleason, Rudolph L

2014-06-01

316

Modulation of ultrasound to produce multifrequency radiation force1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dynamic radiation force has been used in several types of applications, and is performed by modulating ultrasound with different methods. By modulating ultrasound, energy can be transmitted to tissue, in this case a dynamic force to elicit a low frequency cyclic displacement to inspect the material properties of the tissue. In this paper, different types of modulation are explored including amplitude modulation (AM), double sideband suppressed carrier amplitude modulation AM, linear frequency...

2010-01-01

317

New identities among gauge theory amplitudes  

Energy Technology Data Exchange (ETDEWEB)

Color-ordered amplitudes in gauge theories satisfy non-linear identities involving amplitude products of different helicity configurations. We consider the origin of such identities and connect them to the Kawai-Lewellen-Tye (KLT) relations between gravity and gauge theory amplitudes. Extensions are made to one-loop order of the full N=4 super Yang-Mills multiplet.

Bjerrum-Bohr, N.E.J., E-mail: bjbohr@nbi.d [Niels Bohr International Academy and Discovery Center, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Damgaard, Poul H. [Niels Bohr International Academy and Discovery Center, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Feng Bo [Center of Mathematical Science, Zhejiang University, Hangzhou (China); Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Sondergaard, Thomas [Niels Bohr International Academy and Discovery Center, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

2010-08-09

318

Residual DPCM about Motion Compensated Residual Signal for H.264 Lossless Coding  

Science.gov (United States)

In this letter, a new Inter lossless coding method based on a residual DPCM (Differential Pulse Code Modulation) is proposed to improve compression ratio in the H.264 standard. Since the spatial correlation in a residual block can be further exploited among the residual signals after motion estimation/compensation, horizontal or vertical DPCM in the residual signals can be applied to further reduce the magnitudes of the residual signals. The proposed method reduces the average bitrates of 3.5% compared with the Inter lossless coding of the H.264 standard.

Han, Ki-Hun; Rao, Kamisetty R.; Lee, Yung-Lyul

319

Compact dynatron modulator  

CERN Document Server

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

320

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

 
 
 
 
321

Quantum Amplitude Amplification and Estimation  

CERN Document Server

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

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

2000-01-01

322

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

2008-04-01

323

Josephson superlattices and low-amplitude gap solitons  

International Nuclear Information System (INIS)

We have examined the amplitude dependence of the transmission properties in the natural gap of a finite Josephson transmission line and in the first artificial gap of a finite Josephson superlattice. We show that the nonlinear transmission response of both systems exhibits gap-soliton-mediated bistability and hysteresis and can approach unity, once the amplitude of the incoming wave is greater than a certain threshold which is frequency dependent and also decreases with the length of the system. Our computer experiments on the dynamics of wave transmission, which show how the systems would behave in practice, are in good agreement with our calculations and the theoretical predictions in the literature for other kinds of superlattices. We have observed that the modulational instability in the Benjamin-Feir sense which may appear in some computer experiments is eliminated if one considers weak dissipative systems

1990-05-15

324

All-fibre source of amplitude-squeezed light pulses  

CERN Multimedia

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

325

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

Directory of Open Access Journals (Sweden)

Full Text Available Objectives: The amplitude of the auditory steady-state response (ASSR is enhanced in tinnitus. As ASSR ampli¬tude is also enhanced by attention, the effect of tinnitus on ASSR amplitude could be interpreted as an effect of attention mediated by tinnitus. As attention effects on the N1 are signi¬fi¬cantly larger than those on the ASSR, if the effect of tinnitus on ASSR amplitude were due to attention, there should be similar amplitude enhancement effects in tinnitus for the N1 component of the auditory evoked response. Methods: MEG recordings of auditory evoked responses which were previously examined for the ASSR (Diesch et al. 2010 were analysed with respect to the N1m component. Like the ASSR previously, the N1m was analysed in the source domain (source space projection. Stimuli were amplitude-modulated tones with one of three carrier fre¬quen¬cies matching the tinnitus frequency or a surrogate frequency 1½ octaves above the audio¬metric edge frequency in con¬trols, the audiometric edge frequency, and a frequency below the audio¬metric edge Results: In the earlier ASSR study (Diesch et al., 2010, the ASSR amplitude in tinnitus patients, but not in controls, was significantly larger in the (surrogate tinnitus condition than in the edge condition. In the present study, both tinnitus patients and healthy controls show an N1m-amplitude profile identical to the one of ASSR amplitudes in healthy controls. N1m amplitudes elicited by tonal frequencies located at the audiometric edge and at the (surrogate tinnitus frequency are smaller than N1m amplitudes elicited by sub-edge tones and do not differ among each other. Conclusions: There is no N1-amplitude enhancement effect in tinnitus. The enhancement effect of tinnitus on ASSR amplitude cannot be accounted for in terms of attention induced by tinnitus.

EugenDiesch

2012-05-01

326

Weak etalon effect in wave plates can introduce significant FM-to-AM modulations in complex laser systems.  

Science.gov (United States)

The conversion of frequency modulation to amplitude modulation (FM-to-AM) effect is harmful to the high power laser facility based on the phase modulation technique. The FM-to-AM effect of phase modulation pulse induced by the weak etalon effect in wave plates was investigated theoretically and experimentally. A bulk phase modulator with a modulation frequency of 9.2GHz was employed. The numerical simulation results show that the FM-to-AM effect with a temporal modulation depth of 2.5% and 29.7% on the top of the pulse shape was induced by the weak etalon effect in half-wave plate with thickness of 1mm and residual reflectance ratio of 0.5% for 1 pass and 12 passes respectively. On the same condition, the temporal modulation depth is 3.0% and 23.4% respectively in the experiment. The results are in good agreement with numerical simulation results. To our knowledge, it is the first time to introduce the weak etalon effect in wave plates for a complex phase modulation laser system. PMID:20389686

Dangpeng, Xu; Jianjun, Wang; Mingzhong, Li; Honghuan, Lin; Rui, Zhang; Ying, Deng; Qinghua, Deng; Xiaodong, Huang; Mingzhe, Wang; Lei, Ding; Jun, Tang

2010-03-29

327

On the singularities of massive superstring amplitudes  

Science.gov (United States)

Superstring one-loop amplitudes with massive external states are shown to be in general ill-defined due to internal on-shell propagators. However, we argue that since any massive string state (in the uncompactified theory) has a finite lifetime to decay into massless particles, such amplitudes are not terms in the perturbative expansion of physical S-matrix elements: these can be defined only with massless external states. Consistent massive amplitudes require an off-shell formalism.

Foda, Omar

1987-06-01

328

On the singularities of massive superstring amplitudes  

International Nuclear Information System (INIS)

Superstring one-loop amplitudes with massive external states are shown to be in general ill-defined due to internal on-shell propagators. However, we argue that since any massive string state (in the uncompactified theory) has a finite lifetime to decay into massless particles, such amplitudes are not terms in the perturbative expansion of physical S-matrix elements: These can be defined only with massless external states. Consistent massive amplitudes repuire an off-shell formalism. (orig.)

1987-06-04

329

On the singularities of massive superstring amplitudes  

Energy Technology Data Exchange (ETDEWEB)

Superstring one-loop amplitudes with massive external states are shown to be in general ill-defined due to internal on-shell propagators. However, we argue that since any massive string state (in the uncompactified theory) has a finite lifetime to decay into massless particles, such amplitudes are not terms in the perturbative expansion of physical S-matrix elements: These can be defined only with massless external states. Consistent massive amplitudes repuire an off-shell formalism.

Foda, O.

1987-06-04

330

On the singularities of massive superstring amplitudes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Superstring one-loop amplitudes with massive external states are shown to be in general ill-defined due to internal on-shell propagators. However, we argue that since any massive string state (in the uncompactified theory) has a finite lifetime to decay into massless particles, such amplitudes are not terms in the perturbative expansion of physical S-matrix elements: these can be defined only with massless external states. Consistent massive amplitudes require an off-shell formalism.

Foda, O.

1987-01-01

331

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

International Nuclear Information System (INIS)

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

2005-01-01

332

The quadrupole amplitude in the ?N ? ? transition  

International Nuclear Information System (INIS)

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

1992-05-28

333

Observational studies of Cepheid amplitudes. I - Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes  

CERN Document Server

Aims: We attempt to revise the period-amplitude (P-A) relationship of Galactic Cepheids based on multi-colour photometric and radial velocity data. Reliable P-A graphs for Galactic Cepheids constructed for the U, B, V, R_C, and I_C photometric bands and pulsational radial velocity variations facilitate investigations of previously poorly studied interrelations between observable amplitudes. The effects of both binarity and metallicity on the observed amplitude, and the dichotomy between short- and long-period Cepheids can both be studied. Results: Large amplitude Cepheids with companions exhibit smaller photometric amplitudes on average than solitary ones, as expected, while s-Cepheids pulsate with an rbitrary (although small) amplitude. The ratio of the observed radial velocity to blue photometric amplitudes, A_V_RAD/A_B, is not as good an indicator of the ulsation mode as predicted theoretically. This may be caused by an incorrect mode assignment to a number of small amplitude Cepheids, which are not ecessa...

Klagyivik, Peter

2009-01-01

334

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

CERN Multimedia

The Nonlinear Schr\\"odinger (NLS) equation is used to model surface waves in wave tanks of hydrodynamic laboratories. Analysis of the linearized NLS equation shows that its harmonic solutions with a small amplitude modulation have a tendency to grow exponentially due to the so-called Benjamin-Feir instability. To investigate this growth in detail, we relate the linearized solution of the NLS equation to a fully nonlinear, exact solution, called soliton on finite background. As a result, we find that in the range of instability the maximum amplitude increase is finite and can be at most three times the initial amplitude.

Karjanto, N; Peterson, P

2011-01-01

335

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

Directory of Open Access Journals (Sweden)

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

FriniKarayanidis

2014-04-01

336

Full amplitude models of 15 day Cepheids  

Energy Technology Data Exchange (ETDEWEB)

Numerical models of Cepheids have been computed with a range of effective temperatures and compositions. The amplitudes increase if the helium abundance increases or if the effective temperature decreases. The latter effect is contrary to observational data. The models also exhibit velocity amplitudes which are much lower than those observed.

Cogan, B.C.; Cox, A.N.; King, D.S.

1980-01-01

337

Constructing QCD one-loop amplitudes  

CERN Document Server

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 behaviour of the cut integrand as the unconstrained parameters of a specifically chosen parametersiation of the cut loop momentum approach infinity.

Forde, D

2007-01-01

338

On loop amplitudes in the fermionic string  

International Nuclear Information System (INIS)

One loop fermionic string amplitudes with up to four massless (bosonic) external legs are calculated in Polvakov's approach and shown to agree with the ones in operator formalism. Some of the ingredients necessary to prove the vanishing of the multiloop amplitudes with up to three external legs are also discussed. (author)

1986-01-01

339

Helicity amplitudes for matter-coupled gravity  

International Nuclear Information System (INIS)

The Weyl-van der Waerden spinor formalism is applied to the evaluation of helicity invariant amplitudes in the framework of linearized gravitation. The graviton couplings to spin-0, 1 _- _2, 1, and 3 _- _2 particles are given, and, to exhibit the reach of this method, the helicity amplitudes for the process electron + positron ? photon + graviton are obtained. (author)

1992-01-01

340

Validity of certain soft photon amplitudes  

CERN Multimedia

Certain soft photon amplitudes which have been recently suggested as alternatives to the usual Low form of the soft photon approximation are studied and it is demonstrated that problems exist in their relation to the corresponding non-radiative amplitude. The non-radiative amplitude, which is an input to soft photon calculations, is in certain cases required to be evaluated outside of its physical phase space region. Also, for the case of two-body identical particle bremsstrahlung processes, the symmetrized or antisymmetrized form of these soft photon amplitudes cannot be written in terms of the symmetrized or antisymmetrized amplitude for the non-radiative process. It is found that the usual Low form of the soft photon theorem is essentially unaffected by these problems.

Welsh, M; Welsh, Mark; Fearing, Harold W

1996-01-01

 
 
 
 
341

New relations for gauge-theory amplitudes  

International Nuclear Information System (INIS)

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

2008-10-15

342

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

International Nuclear Information System (INIS)

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

2010-06-01

343

?- and K-meson Bethe-Salpeter amplitudes  

International Nuclear Information System (INIS)

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

1997-12-01

344

DETERMINISTIC COMPONENTS IN THE LIGHT CURVE AMPLITUDE OF Y OPH  

International Nuclear Information System (INIS)

About two decades after the discovery of the amplitude decline of the light curve of the classical Cepheid Y Oph, its study is resumed using an increased amount of homogenized data and an extended time base. In our approach, the investigation of different time series concerning the light curve amplitude of Y Oph is not only the reason for the present study, but also a stimulus for developing a coherent methodology for studying long- and short-term variability phenomena in variable stars, taking into account the details of concrete observing conditions: amount of data, data sampling, time base, and individual errors of observational data. The statistical significance of this decreasing trend was estimated by assuming its linearity. We approached the decision-making process by formulating adequate null and alternative hypotheses, and testing the value of the regression line slope for different data sets via Monte Carlo simulations. A variability analysis, through various methods, of the original data and of the residuals obtained after removing the linear trend was performed. We also proposed a new statistical test, based on amplitude spectrum analysis and Monte Carlo simulations, intended to evaluate how detectible is a given (linear) trend in well-defined observing conditions: the trend detection probability. The main conclusion of our study on Y Oph is that, even if the false alarm probability is low enough to consider the decreasing trend to be statistically significant, the available data do not allow us to obtain a reasonably powerful test. We are able to confirm the light curve amplitude decline, and the order of magnitude of its slope with a better statistical substantiation. According to the obtained values of the trend detection probability, it seems that the trend we are dealing with is marked by a low detectibility. Our attempt to find signs of possible variability phenomena at shorter timescales ended by emphasizing the relative constancy of our data, within their precision limits.

2010-02-01

345

Regulation of motor representation by phase-amplitude coupling in the sensorimotor cortex.  

Science.gov (United States)

High-? amplitude (80-150 Hz) represents motor information, such as movement types, on the sensorimotor cortex. In several cortical areas, high-? amplitudes are coupled with low-frequency phases, e.g., ? and ? (phase-amplitude coupling, PAC). However, such coupling has not been studied in the sensorimotor cortex; thus, its potential functional role has yet to be explored. We investigated PAC of high-? amplitude in the sensorimotor cortex during waiting for and the execution of movements using electrocorticographic (ECoG) recordings in humans. ECoG signals were recorded from the sensorimotor cortices of 4 epilepsy patients while they performed three different hand movements. A subset of electrodes showed high-? activity selective to movement type around the timing of motor execution, while the same electrodes showed nonselective high-? activity during the waiting period (>2 s before execution). Cross frequency coupling analysis revealed that the high-? amplitude during waiting was strongly coupled with the ? phase (10-14 Hz) at the electrodes with movement-selective high-? amplitudes during execution. This coupling constituted the high-? amplitude peaking around the trough of the ? oscillation, and its strength and phase were not predictive of movement type. As the coupling attenuated toward the timing of motor execution, the high-? amplitude appeared to be released from the ? phase to build a motor representation with phase-independent activity. Our results suggest that PAC modulates motor representation in the sensorimotor cortex by holding and releasing high-? activity in movement-selective cortical regions. PMID:23115184

Yanagisawa, Takufumi; Yamashita, Okito; Hirata, Masayuki; Kishima, Haruhiko; Saitoh, Youichi; Goto, Tetsu; Yoshimine, Toshiki; Kamitani, Yukiyasu

2012-10-31

346

Residue analysis in linearized elastic inversion  

Energy Technology Data Exchange (ETDEWEB)

Amplitude-versus-Offset (AVA) information is used for estimation of the elastic parameters. We introduce a method based on the linearized Zoeppritz equation to separate the linear AVA behavior from the nonlinear and noise terms, which we call the residue. This residue is used to analyze the influence of errors, noise and nonlinear terms on the resolution of the linear inversion. The problem of interference of thin layers has been addressed and a new method to avoid the apparent AVA due to this layering is shown.

Wijngaarden, A.J. van; Wapenaar, P.A. [Delft Univ. of Technology (Netherlands)

1995-12-31

347

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

Directory of Open Access Journals (Sweden)

Full Text Available Attitude maneuvers of a Communication Technology Satellite (CTS-like spacecraft using constant-amplitude thrusters is of great importance. The spacecraft consists of a rigid main body and two symmetrical solar panels. When the panels are large, they cannot be treated as rigid bodies anymore. They are supposed to behave structural flexibility. To discrete their motion, the finite element method is followed. Under constant-amplitude thrusts, steady-state attitude angle oscillations may occur in large amplitude after the maneuvers. Since, the spacecraft should point to the earth precisely, these oscillations must be reduced into small permissible values. To reduce residual attitude angle oscillations, Proportional Derivative (PD based constant-amplitude input shaping logic is proposed to determine time locations of thruster switching. Then, under such inputs, attitude maneuvers of the spacecraft are simulated numerically. Results of simulations show that the precise orientation of the satellite can be achieved.

Edward Halawa

2012-01-01

348

Helicity Amplitudes and Angular Decay Distributions  

CERN Document Server

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

Körner, J G

2014-01-01

349

A Method and an Apparatus for Generating a Phase-Modulated Wave Front of Electromagnetic Radiation  

DEFF Research Database (Denmark)

The present invention provides a method and a system for generating a phase-modulated wave front. According to the present invention, the spatial phase-modulation is not performed on the different parts of the wave front individually as in known POSLMs. Rather, the spatial phase-modulation of the present invention is performed by generating an amplitude modulation in the wave front, Fourier or Fresnel transforming the amplitude modulated wave front, filtering Fourier or Fresnel components of the Fourier or Fresnel distribution with a spatial filter such as a phase contrast filter, and regenerating the wave front whereby the initial amplitude modulation has transformed into a phase-modulation.

Glückstad, Jesper Technical University of Denmark,

350

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

351

Amplitude Variations in Pulsating Yellow Supergiants  

CERN Document Server

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

Percy, John R

2014-01-01

352

The singular behavior of massive QCD amplitudes  

International Nuclear Information System (INIS)

We discuss the structure of infrared singularities in on-shell QCD amplitudes with massive partons and present a general factorization formula in the limit of small parton masses. The factorization formula gives rise to an all-order exponentiation of both, the soft poles in dimensional regularization and the large collinear logarithms of the parton masses. Moreover, it provides a universal relation between any on-shell amplitude with massive external partons and its corresponding massless amplitude. For the form factor of a heavy quark we present explicit results including the fixed-order expansion up to three loops in the small mass limit. For general scattering processes we show how our constructive method applies to the computation of all singularities as well as the constant (mass-independent) terms of a generic massive n-parton QCD amplitude up to the next-to-next-to-leading order corrections. (orig.)

2006-01-01

353

Open String Amplitudes in Various Gauges  

CERN Document Server

Recently, Schnabl constructed the analytic solution of the open string tachyon. Subsequently, the absence of the physical states at the vacuum was proved. The development relies heavily on the use of the gauge condition different from the ordinary one. It was shown that the choice of gauge simplifies the analysis drastically. When we perform the calculation of the amplitudes in Schnabl gauge, we find that the off-shell amplitudes of the Schnabl gauge is still very complicated. In this paper, we propose the use of the propagator in the modified Schnabl gauge and show that this modified use of the Schnabl gauge simplifies the computation of the off-shell amplitudes drastically. We also compute the amplitudes of open superstring in this gauge.

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

2007-01-01

354

Constant-amplitude, frequency- independent phase shifter  

Science.gov (United States)

Electronic circuit using operational amplifiers provides output with constant phase shift amplitude, with respect to sinusoidal input, over wide range of frequencies. New circuit includes field effect transistor, Q, operational amplifiers, A1 and A2, and phase detector.

Deboo, G. J.

1971-01-01

355

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

356

Regge amplitudes with crossing and unitarity  

International Nuclear Information System (INIS)

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

1976-07-21

357

String amplitudes as solutions to soliton equations  

International Nuclear Information System (INIS)

Tree and one-loop bosonic string amplitudes are shown to be given by solutions to the Kadomtsev-Petviashvili hierarchy of soliton equations whose solutions are completely known. Generalization to all Polyakov strings is discussed

1987-09-15

358

Sensitivity of nonlinear fiber CPA-systems to initial spectral amplitude and spectral phase ripples  

Science.gov (United States)

Pulse-contrast degradation at the CPA-system's output is analyzed. If Kerr-nonlinearity is present, weak initial spectral phase and amplitude modulations are responsible for the decrease. The pulse is split into several sub-pulses. Bessel-functions describe the intensities of the side-pulses relative to the principal pulse. We provide the governing physical quantities.

Schimpf, D. N.; Seise, E.; Limpert, J.; Tünnermann, A.

2009-02-01

359

Performance of a monolithic time-to-amplitude converter for high precision TOF measurements  

Energy Technology Data Exchange (ETDEWEB)

A monolithic time-to-amplitude converter integrated circuit was designed and built with a semicustom bipolar IC technology. In order to evaluate the performance of the IC, it was incorporated into a CAMAC TDC module. We observed a resolution of 50 ps with high stability against temperature variation and external disturbance. This performance was achieved by using the differential TAC technique. (orig.).

Tanaka, Manobu; Ikeda, Hirokazu; Ikeda, Mitsuo; Inaba, Susumu (National Lab. for High Energy Physics, Oho, Tsukuba (Japan))

1992-02-15

360

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

Directory of Open Access Journals (Sweden)

Full Text Available Amplitude modulated continuous wave (AMCW lidar systems commonly suffer from non-linear phase and amplitude responses due to a number of known factors such as aliasing and multipath inteference. In order to produce useful range and intensity information it is necessary to remove these perturbations from the measurements. We review the known causes of non-linearity, namely aliasing, temporal variation in correlation waveform shape and mixed pixels/multipath inteference. We also introduce other sources of non-linearity, including crosstalk, modulation waveform envelope decay and non-circularly symmetric noise statistics, that have been ignored in the literature. An experimental study is conducted to evaluate techniques for mitigation of non-linearity, and it is found that harmonic cancellation provides a significant improvement in phase and amplitude linearity.

John P. Godbaz

2011-12-01

 
 
 
 
361

Protecting quantum entanglement from amplitude damping  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently stu...

Liao, Zeyang; Al-amri, M.; Zubairy, M. Suhail

2012-01-01

362

Nucleon distribution amplitudes from lattice QCD  

CERN Document Server

We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MSbar scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature.

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

2008-01-01

363

Effective gluon interactions from superstring disk amplitudes  

International Nuclear Information System (INIS)

In this thesis an efficient method for the calculation of the N-point tree-level string amplitudes is presented. Furthermore it is shown that the six-gluon open-superstring disk amplitude can be expressed by a basis of six triple hypergeometric functions, which encode the full ?' dependence. In this connection material for obtaining the ?' expansion of these functions is derived. Hereby many Euler-Zagier sums are calculated including multiple harmonic series. (HSI)

2006-01-01

364

Nucleon distribution amplitudes from lattice QCD  

International Nuclear Information System (INIS)

We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature. (orig.)

2008-01-01

365

Nucleon distribution amplitudes from lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature. (orig.)

Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Kaltenbrunner, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (DE). John von Neumann-Inst. fuer Computing NIC] (and others)

2008-04-15

366

Seismic directional beamforming using cosine amplitude distribution  

Science.gov (United States)

o improve the signal-to-noise ratio in seismic exploration, we studied the method of time domain seismic beam-forming based on receiver array (TSBBRA). TSBBRA is useful to extract reflected waves from some target layers and decrease noise from other direction. When noise is strong enough, the control parameter of the method of TSBBRA need to be increased. It means that we have to use more raw records to form a directional seismic record. Therefore, the signal energy in beam is much denser, and the beam becomes narrower accordingly. When the beam can not cover the receiver array, the signal-to-noise ratios in different traces are quite unbalanced and average quality of data probably is still quite low. Therefore, this paper proposes seismic directional beamforming using the cosine amplitude distribution (SDBCAD). SDBCAD can adjust seismic beam shape by introducing cosine amplitude distribution, an amplitude weighting method, in the procedure of beamforming. We studied cosine amplitude weighting function, analyzed the characteristics of uniform and cosine amplitude distribution in beamforming, and compared directivity of beams from the two kind of amplitude pattern. It shows that the main beam of cosine-weighted amplitude is different from uniform distribution. The coverage of main beam from SDBCAD is wider than uniform amplitude, and the width of beam is varied with different number of cosine order. So we simulated the seismic raw record, and used TSBBRA and SDBCAD to process simulated data at the receiving array. The results show that SDBCAD can broaden directional beam, and the main beam from SDBCAD can cover the entire traces instead of partial coverage in TSBBRA. The average signal-to-noise ratio increased 0.2~4.5dB. It concludes that SDBCAD is competent to stretch beam reasonable, and it is useful to boost signal-to-noise ratio when beam from TSBBRA is too narrow to illuminate receiver array properly. Updated results will be presented at the meeting.

Jiang, T.; Xu, X.; Song, J.; Jia, H.; Ge, L.

2013-12-01

367

All loop N = 2 string amplitudes  

CERN Multimedia

Using the N=4 topological reformulation of N=2 strings, we compute all loop partition function for special compactifications of N=2 strings as a function of target moduli. We also reinterpret N=4 topological amplitudes in terms of slightly modified N=2 topological amplitudes. We present some preliminary evidence for the conjecture that N=2 strings is the large N limit of Holomorphic Yang-Mills in 4 dimensions.

Ooguri, H; Ooguri, Hirosi; Vafa, Cumrun

1995-01-01

368

Effective gluon interactions from superstring disk amplitudes  

Energy Technology Data Exchange (ETDEWEB)

In this thesis an efficient method for the calculation of the N-point tree-level string amplitudes is presented. Furthermore it is shown that the six-gluon open-superstring disk amplitude can be expressed by a basis of six triple hypergeometric functions, which encode the full {alpha}' dependence. In this connection material for obtaining the {alpha}' expansion of these functions is derived. Hereby many Euler-Zagier sums are calculated including multiple harmonic series. (HSI)

Oprisa, D.

2006-05-15

369

Simple parametrization of the. pi. -N amplitude  

Energy Technology Data Exchange (ETDEWEB)

We present a simple parametrization of the S-, P-, and D-wave ..pi..-N amplitudes using separable potentials for T/sub ..pi../<1 GeV. The effect of the inelasticity is included in the Green's function while maintaining consistency with unitarity. The P/sub 11/ amplitude is written as a pole plus nonpole in order to describe pion absorption in A> or =2.

McLeod, R.J.; Afnan, I.R.

1985-07-01

370

Heterotic approach to the nucleon distribution amplitude  

Science.gov (United States)

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

Bergmann, M.; Stefanis, N. G.

1994-04-01

371

Helicity amplitudes for matter-coupled gravity  

Science.gov (United States)

The great simplicity attained by the Weyl-van der Waerden spinor technique in the evaluation of helicity invariant amplitudes is shown to apply in the cumbersome calculations within the framework of linearized gravitation. Once the graviton couplings to spin-0, 1/2, 1, and 3/2 particles are given, we exhibit the reach of this method by evaluating, as an example, the helicity amplitudes for the process electron + positron ? photon + graviton in a very straightforward way.

Aldrovandi, R.; Novaes, S. F.; Spehler, D.

1994-04-01

372

Amplitudes and Cross Sections at the LHC  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We describe the elements of the GLM model that successfully describes soft hadronic interactions at energies from ISR to LHC. This model is based on a single Pomeron with a large intercept $\\Delta_{\\pom}$ = 0.23 and slope $\\alpha_{\\pom}'$ = 0, and so provides a natural matching with perturbative QCD. We analyze the elastic, single diffractive and double diffractive amplitudes, and compare the behaviour of the GLM amplitudes to those of other parameterizations. We summar...

Gotsman, Errol

2013-01-01

373

Branching Brownian Motion from Quantized Heat Amplitudes  

CERN Document Server

Heat amplitudes are shown to possess Lagrangian dynamics equivalent to the heat equation. Quantization of heat amplitudes then leads to discrete particles performing Brownian motion. The propagator for free Brownian motion is derived and shown to give the classical expression for the transition probability of a Brownian particle. An exponential clock is seen to be naturally contained in the formalism. Interactions are introduced and the Feynman series for a 'branching and dying' model is exactly summed.

Schuller, F P; Schuller, Frederic P.; Vogt, Pascal

2003-01-01

374

Effect of Modulation Error on All Optical Fiber Current Transformers  

Directory of Open Access Journals (Sweden)

Full Text Available For actively modulated In-line Sagnac interferential all optic fiber current transformers (AOFCTs, the accuracies are directly affected by the amplitude of the modulation signal. In order to deeply undertand the function of the modulator, a theoretical model of modulation effect to AOFCTs is built up in this paper. The effect of the amplitude of the modulation signal to the output intensity of AOFCTs is theoretically formulated and numerical calculated. The results show that the modulation voltage variation could affect the output accuracies significantly. This might be some references on the investigation for practical applications of AOFCTs.

Zhengping Wang

2012-12-01

375

Online tracking of instantaneous frequency and amplitude of dynamical system response  

Science.gov (United States)

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

Frank Pai, P.

2010-05-01

376

Phase-to-amplitude data page conversion for holographic storage and optical encryption.  

Science.gov (United States)

A new phase-to-amplitude data page conversion method is proposed for efficient recovery of the data encoded in phase-modulated data pages used in holographic storage and optical encryption. The method is based on the interference between the data page and its copy shifted by an integral number of pixels. Key properties such as Fourier plane homogeneity, bit error rate, and positioning tolerances are investigated by computer modeling, and a comparison is provided with amplitude-modulated data page holographic storage with and without static phase masks. The feasibility and the basic properties of the proposed method are experimentally demonstrated. The results show that phase-modulated data pages can be used efficiently with reduced system complexity. PMID:17514316

Koppa, Pál

2007-06-10

377

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

378

Scattering amplitudes in open superstring theory  

International Nuclear Information System (INIS)

The present thesis deals with the theme field of the scattering amplitudes in theories of open superstrings. Especially two different formalisms for the handling of superstrings are introduced and applied for the calaculation of tree-level amplitudes - the Ramond- Neveu-Schwarz (RNS) and the Pure-Spinor (PS) formalism. The RNS approach is proved as flexible in order to describe compactification of the initially ten flat space-time dimensions to four dimensions. We solve the technical problems, which result from the interacting basing world-sheet theory with conformal symmetry. This is used to calculate phenomenologically relevant scattering amplitudes of gluons and quarks as well as production rates of massive harmonic vibrations, which were already identified as virtual exchange particles on the massless level. In the case of a low string mass scale in the range of some Tev the string-specific signatures in parton collisions can be observed in the near future in the LHC experiment at CERN and indicated as first experimental proof of the string theory. THose string effects occur universally for a wide class of string ground states respectively internal geometries and represent an elegant way to avoid the so-called landscape problem of the string theory. A further theme complex in this thesis is based on the PS formalism, which allows a manifestly supersymmetric treatment of scattering amplitudes in ten space-time dimension with sixteen supercharges. We introduce a family of superfields, which occur in massless amplitudes of the open string and can be naturally identified with diagrams of three-valued knots. Thereby we reach not only a compact superspace representation of the n-point field-theory amplitude but can also write the complete superstring n-point amplitude as minimal linear combination of partial amplitudes of the field theory as well as hypergeometric functions. The latter carry the string effects and are analyzed from different perspectives, above all with regards to the duality between group-theoretical and kinematic contributions to tree-level amplitudes observed in the field theory.

2011-01-01

379

The output amplitude prediction of crystal oscillator  

Science.gov (United States)

Crystal oscillator is an important component of the microwave and RF devices. One of the most important characteristics of crystal oscillators is phase noise spectrum. Phase noise within the half-bandwidth of the loop is closely related to the loaded quality factor QL. According to our research about Pierce oscillator circuit, we can derive that phase noise improves with increasing QL and an appropriate increase in the value of collector-to-ground capacitance C1 can improve QL. However, to change the value of C1 also affects the output amplitude of oscillation circuit. In the paper, the method of predicting output amplitude is presented and a prototype 50 MHz AT-cut 3rd overtone Pierce low phase noise crystal oscillator is designed. The output amplitude variation versus the value of C1 can be obtained with MATLAB. On the premise of specific value of C1, the values of other circuit parameters are changed to make sure that output amplitude is maintained in the required value range. A design of the prototype 50MHz Pierce crystal oscillator is presented and the experiments are carried out. The measurement phase noise results are -126 dBc/Hz@100Hz and -151 dBc/Hz@1KHz. Experimental result shows it is necessary to predict the output amplitude of crystal oscillators.

Wang, Yan; Huang, Xianhe

2013-03-01

380

Finite amplitude thermal convection with variable gravity  

Directory of Open Access Journals (Sweden)

Full Text Available Finite amplitude thermal convection is studied in a horizontal layer of infinite Prandtl number fluid with a variable gravity. For the present study, gravity is restricted to vary quadratically with respect to the vertical variable. A perturbation technique based on a small parameter, which is a measure of the ratio of the vertical to horizontal dimensions of the convective cells, is employed to determine the finite amplitude steady solutions. These solutions are represented in terms of convective modes whose amplitudes can be either small or of order unity. Stability of these solutions is investigated with respect to three dimensional disturbances. A variable gravity function introduces two non-dimensional parameters. For certain range of values of these two parameters, double or triple cellular structure in the vertical direction can be realized. Hexagonal patterns are preferred for sufficiently small amplitude of convection, while square patterns can become dominant for larger values of the convective amplitude. Variable gravity can also affect significantly the wavelength of the cellular pattern and the onset condition of the convective motion.

Albert T. Hsui

2001-01-01

 
 
 
 
381

RESIDUATED WEAK LATTICES  

Directory of Open Access Journals (Sweden)

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

M. BASHEER AHAMED

2010-12-01

382

Scaling of saturation amplitudes in baroclinic instability  

International Nuclear Information System (INIS)

By using finite-amplitude conservation laws for pseudomomentum and pseudoenergy, rigorous upper bounds have been derived on the saturation amplitudes in baroclinic instability for layered and continuously-stratified quasi-geostrophic models. Bounds have been obtained for both the eddy energy and the eddy potential enstrophy. The bounds apply to conservative (inviscid, unforced) flow, as well as to forced-dissipative flow when the dissipation is proportional to the potential vorticity. This approach provides an efficient way of extracting an analytical estimate of the dynamical scalings of the saturation amplitudes in terms of crucial non-dimensional parameters. A possible use is in constructing eddy parameterization schemes for zonally-averaged climate models. The scaling dependences are summarized, and compared with those derived from weakly-nonlinear theory and from baroclinic-adjustment estimates

1994-02-01

383

Duality and effective amplitudes in quantum chromodynamics  

International Nuclear Information System (INIS)

This work is an attempt to relate the partonic and hadronic phases of strong interactions by means of a model of effective string amplitudes which take into account color coherence without the need to restrict the phase-space. The basic idea of this approach is to construct, from open superstrings, string amplitudes which give, at the zero slope limit, QCD amplitudes. The running parameters (coupling and slope) of the model are constrained by perturbative QCD and by the consistency of string quantization. When the running slope becomes equal to the hadronic one, the model can be used in the hadronic sector. This approach could provide some hints about the effective string theory of QCD, and a better understanding of the parton-hadron duality

1991-01-01

384

Weak phases from topological-amplitude parametrization  

CERN Document Server

We propose a parametrization for two-body nonleptonic $B$ meson decays, in which the various topologies of amplitudes are counted in terms of powers of the Wolfenstein parameter $\\lambda\\sim 0.22$. The weak phases and the amplitudes are determined by comparing this parametrization with available measurements. It is possible to obtain the phase $\\phi_3$ from the $B\\to K\\pi$ data up to theoretical uncertainty of $O(\\lambda^3)\\sim 1%$. The recently measured $B_d^0\\to\\pi^0\\pi^0$ branching ratio implies a large color-suppressed or penguin amplitude, and that the extraction of the phase $\\phi_2$ from the $B\\to\\pi\\pi$ data may suffer theoretical uncertainty more than the expected one of $O(\\lambda^2)\\sim 5%$.

Charng, Y Y; Charng, Yeo-Yie; Li, Hsiang-nan

2003-01-01

385

On Arbitrary Phases in Quantum Amplitude Amplification  

CERN Multimedia

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

Hoyer, P

2000-01-01

386

Zeroing in on Supersymmetric Radiation Amplitude Zeros  

CERN Document Server

Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p_T spectrum of the softest lepton in the trilepton $\\chi_1^\\pm \\chi_2^0$ decay channel to that of a control process such as $\\chi_1^+ \\chi_1^-$ or $\\chi_2^0 \\chi_2^0$. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.

Hewett, JoAnne L; Rizzo, Thomas G

2011-01-01

387

Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly  

CERN Document Server

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

Nikolov, Nikolay M; Todorov, Ivan

2013-01-01

388

Electro-Optic Modulation of Single Photons  

CERN Document Server

We use the Stokes photon of a biphoton pair to set the time origin for electro-optic modulation of the wave function of the anti-Stokes photon thereby allowing arbitrary phase and amplitude modulation. We demonstrate conditional single-photon wave functions composed of several pulses, or instead, having gaussian or exponential shapes.

Kolchin, Pavel; Du, Shengwang; Yin, G Y; Harris, S E

2008-01-01

389

Electro-Optic Modulation of Single Photons  

International Nuclear Information System (INIS)

We use the Stokes photon of a biphoton pair to set the time origin for electro-optic modulation of the wave function of the anti-Stokes photon thereby allowing arbitrary phase and amplitude modulation. We demonstrate conditional single-photon wave functions composed of several pulses, or instead, having Gaussian or exponential shapes

2008-09-05

390

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

391

New Amplitude Equations for Thin Elastic Rods  

International Nuclear Information System (INIS)

The stability of twisted straight rods is described within the framework of the time dependent Kirchhoff equations for thin elastic filaments. A perturbation method is developed to study the linear stability of this problem and find the dispersion relations. A nonlinear analysis results in a new amplitude equation, describing the deformation of the rod beyond the instability, which takes the form of a pair of nonlinear, second-order evolution equations coupling the local deformation amplitude to the twist density. Various solutions, such as solitary waves, are presented. copyright 1996 The American Physical Society

1996-10-01

392

Protecting quantum entanglement from amplitude damping  

International Nuclear Information System (INIS)

Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently studied methods, the scheme presented here does not require weak measurement in the reversal process, leading to a faster recovery of entanglement. We propose a possible experimental implementation based on linear optical system. (paper)

2013-07-28

393

High energy multi-gluon exchange amplitudes  

International Nuclear Information System (INIS)

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

1980-01-01

394

Nucleon distribution amplitude: The heterotic solution  

Science.gov (United States)

We present a new nucleon distribution amplitude which amalgamates features of the Chernyak-Ogloblin-Zhitnitsky model with those of the Gari-Stefanis model. This ``heterotic'' solution provides the possibility to have asymptotically a small ratio ||GnM||/GpM<=0.1, while satisfying most of the sum-rule requirements up to third order. Using this nucleon distribution amplitude we calculate the electromagnetic and weak nucleon form factors, the transition form factor ?p?+, and the decay widths of the charmonium levels 3S1, 3P1, and 3P2 into pp¯. The agreement with the available data is remarkable in all cases.

Stefanis, N. G.; Bergmann, M.

1993-05-01

395

Gluon scattering amplitudes at strong coupling  

Energy Technology Data Exchange (ETDEWEB)

We describe how to compute planar gluon scattering amplitudes at strong coupling in N = 4 super Yang Mills by using the gauge/string duality. The computation boils down to finding a certain classical string configuration whose boundary conditions are determined by the gluon momenta. The results are infrared divergent. We introduce the gravity version of dimensional regularization to define finite quantities. The leading and subleading IR divergencies are characterized by two functions of the coupling that we compute at strong coupling. We compute also the full finite form for the four point amplitude and we find agreement with a recent ansatz by Bern, Dixon and Smirnov.

Alday, Luis F. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, 3508 TD Utrecht (Netherlands); Maldacena, Juan [School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540 (United States)

2007-06-15

396

Amplitudes and Cross Sections at the LHC  

CERN Multimedia

We describe the elements of the GLM model that successfully describes soft hadronic interactions at energies from ISR to LHC. This model is based on a single Pomeron with a large intercept $\\Delta_{\\pom}$ = 0.23 and slope $\\alpha_{\\pom}'$ = 0, and so provides a natural matching with perturbative QCD. We analyze the elastic, single diffractive and double diffractive amplitudes, and compare the behaviour of the GLM amplitudes to those of other parameterizations. We summarize the main features and results of competing models for soft interactions at LHC energies.

Gotsman, Errol

2013-01-01

397

Protecting quantum entanglement from amplitude damping  

Science.gov (United States)

Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently studied methods, the scheme presented here does not require weak measurement in the reversal process, leading to a faster recovery of entanglement. We propose a possible experimental implementation based on linear optical system.

Liao, Zeyang; Al-Amri, M.; Zubairy, M. Suhail

2013-09-01

398

Filamentation instability of large-amplitude Alfven waves  

Science.gov (United States)

An instability that leads to the filamentation of large-amplitude Alfven waves and gives rise to purely growing density and magnetic field fluctuations is studied. The dispersion relation of the instability is derived, from which the threshold conditions and the growth rates of the instability are analyzed quantitatively for applications to the solar wind plasma. Their dependence on the filamentation spectrum, the plasma beta, and the pump frequency and intensity was examined for both right-hand and left-hand circularly polarized Alfven waves. The excitation of filamentation instability for certain cases of interest is discussed and compared with that of the parametric decay and modulation instability. The relevance of the proposed instability to some observations is discussed.

Kuo, S. P.; Whang, M. H.; Lee, M. C.

1988-01-01

399

Waveform Sampler CAMAC Module  

Energy Technology Data Exchange (ETDEWEB)

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

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

1985-09-01

400

Waveform sampler CAMAC module  

International Nuclear Information System (INIS)

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

1986-02-01

 
 
 
 
401

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

CERN Multimedia

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

402

The effect of airway pressure and oscillation amplitude on ventilation in pre-term infants.  

Science.gov (United States)

We determined the effect of lung recruitment and oscillation amplitude on regional oscillation volume and functional residual capacity (FRC) in high-frequency oscillatory ventilation (HFOV) used in pre-term infants with respiratory distress syndrome (RDS). Changes in lung volume, oscillation volume and carbon dioxide levels were recorded in 10 infants during a stepwise recruitment procedure, and an increase in pressure amplitude of 5 cmH(2)O was measured using electrical impedance tomography and transcutaneous monitoring. The pressures at maximal respiratory system compliance, maximal oscillation volume and minimal carbon dioxide levels were determined. Impedance data were analysed for the chest cross-section and predefined regions of interest. Despite the fixed pressure amplitude, the oscillation volume changed during the incremental pressure steps following a parabolic pattern, with an inverse relationship to the carbon dioxide pressures. The pressures corresponding with maximal compliance, maximal oscillation volume and minimal carbon dioxide were similar and highly correlated. Regional analysis showed similar findings. The increase in pressure amplitude resulted in increased oscillation volumes and decreased carbon dioxide levels, while FRC remained unchanged. In HFV pre-term infants with RDS, oscillation volumes are closely related to the position of ventilation in the pressure-volume envelope and the applied pressure amplitude. Changes in pressure amplitude do not seem to affect FRC. PMID:22362852

Miedema, Martijn; de Jongh, Frans H; Frerichs, Inez; van Veenendaal, Mariette B; van Kaam, Anton H

2012-08-01

403

A beam modulator of photoelectric pulse  

International Nuclear Information System (INIS)

This paper describes a beam modulator of photoelectric pulse. It is mainly used to control beam of accelerator and detector system, the repetition frequency of output pulse is controlled by step motor speed controller. This motor is in continuous operation mode. The characteristics of a beam modulator of photoelectric pulse are as follows: An amplitude of +-400 V is employed to modulate beam of accelerator and power PW<100 mw. An amplitude of +-5 V is employed to control ADC. The falling edge of +-400 V is adjustable from 10 ?s-15 ms. The leading edge of +-5 V is adjustable from 10 ?s to 15 ms

1994-10-06

404

Hybrid multinary modulation using a phase modulating spatial light modulator and a low-pass spatial filter.  

Science.gov (United States)

We propose a method for performing binary intensity and continuous phase modulation of beams with a spatial light modulator (SLM) and a low-pass spatial filtering 4-f system. With our method it is possible to avoid the use of phase masks in holographic data storage systems or to enhance the phase encoding of the SLM by making it capable of binary amplitude modulation. The data storage capabilities and the limitations of the method are studied. PMID:17700777

Göröcs, Zoltán; Erdei, Gábor; Sarkadi, Tamás; Ujhelyi, Ferenc; Reményi, Judit; Koppa, Pál; Lorincz, Emoke

2007-08-15

405

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

406

Ward Identities for Amplitudes with Reggeized Gluons  

CERN Document Server

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

Bartels, J; Vacca, G P

2012-01-01

407

Amplitude ambiguities in pseudoscalar meson photoproduction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider the problem of determining amplitudes from observables for the case of pseudoscalar meson photoproduction. We find a number of surprisingly simple constraints which give necessary conditions for a complete set of measurements. These results contradict one of the selection rules derived previously.

Keaton, Greg; Workman, Ron

1995-01-01

408

Audio steganography by amplitude or phase modification  

Science.gov (United States)

This paper presents the results of embedding short covert message utterances on a host, or cover, utterance by modifying the phase or amplitude of perceptually masked or significant regions of the host. In the first method, the absolute phase at selected, perceptually masked frequency indices was changed to fixed, covert data-dependent values. Embedded bits were retrieved at the receiver from the phase at the selected frequency indices. Tests on embedding a GSM-coded covert utterance on clean and noisy host utterances showed no noticeable difference in the stego compared to the hosts in speech quality or spectrogram. A bit error rate of 2 out of 2800 was observed for a clean host utterance while no error occurred for a noisy host. In the second method, the absolute phase of 10 or fewer perceptually significant points in the host was set in accordance with covert data. This resulted in a stego with successful data retrieval and a slightly noticeable degradation in speech quality. Modifying the amplitude of perceptually significant points caused perceptible differences in the stego even with small changes of amplitude made at five points per frame. Finally, the stego obtained by altering the amplitude at perceptually masked points showed barely noticeable differences and excellent data recovery.

Gopalan, Kaliappan; Wenndt, Stanley J.; Adams, Scott F.; Haddad, Darren M.

2003-06-01

409

Amplitude ambiguities in pseudoscalar meson photoproduction  

Energy Technology Data Exchange (ETDEWEB)

We consider the problem of determining amplitudes from observables for the case of pseudoscalar meson photoproduction. We find a number of surprisingly simple constraints which give necessary conditions for a complete set of measurements. These results contradict one of the selection rules derived previously. {copyright} {ital 1996 The American Physical Society.}

Keaton, G.; Workman, R. [Department of Physics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States)

1996-03-01

410

Deconvoluting GPD from an explicit DVCS amplitude  

CERN Document Server

By assuming factorization of the GPD under the deconvolution integral for the hand-bag diagram, we develop a method of solving this integral beyond the cross-over line. As examples we use explicit models of deeply virtual Compton scattering (DVCS) amplitudes to get solution for relevant GPDs.

Bondarenko, K

2013-01-01

411

Particle Distribution Modification by Low Amplitude Modes  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-08-28

412

Infrared singularities in one-loop amplitudes  

Energy Technology Data Exchange (ETDEWEB)

In this talk we discuss a purely numerical approach to next-to-leading order calculations in QCD. We present a simple formula, which provides a local infrared subtraction term for the integrand of a one-loop amplitude. In addition we briefly comment on local ultraviolet subtraction terms and on the required deformation of the contour of integration.

Assadsolimani, M. [Institut fuer Physik, Humboldt-Universitaet zu Berlin, D - 12489 Berlin (Germany); Becker, S.; Reuschle, Ch.; Weinzierl, S. [Institut fuer Physik, Universitaet Mainz, D - 55099 Mainz (Germany)

2010-08-15

413

Particle Distribution Modification by Low Amplitude Modes  

International Nuclear Information System (INIS)

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

2009-01-01

414

Loop amplitudes for the fermionic string  

International Nuclear Information System (INIS)

We obtain simple formulae for loop amplitudes of the fermionic closed oriented Polyakov string in d=10, as integrals over moduli and supermoduli space. The integrals over supermoduli may be carried out, leaving an integral over moduli with respect to the Weil-Petersson measure. The integrand consists of Green functions and determinants of laplacians on tensors and spinors. (orig.)

1986-12-08

415

Fuzzy amplitude densities and stochastic quantum mechanics  

International Nuclear Information System (INIS)

Fuzzy amplitude densities are employed to obtain probability distributions for measurements that are not perfectly accurate. The resulting quantum probability theory is motivated by the path integral formalism for quantum mechanics. Measurements that are covariant relative to a symmetry group are considered. It is shown that the theory includes traditional as well as stochastic quantum mechanics

1989-01-01

416

Phase-stepped television holographic technique for measuring phase and amplitude maps of small vibrations.  

Science.gov (United States)

Phase stepping between frames in TV holography is combined with sinusoidal phase modulation to determine phase and amplitude distributions of objects vibrating with small amplitudes (modal analysis and the determination of harmonic sound fields in air and water. The noise reduction that is obtained with the phase-stepping technique reduces the number of interferograms needed by one-half, which can shorten experimental time. The technique is robust, easy to use, and illustrated by modes of vibration in a simple plate and in a more complicated structure (a violin). PMID:21102776

Saldner, H O

1996-07-10

417

Ultrafast optical pulse repetition rate multiplication based on time domain spectral amplitude/phase filtering  

Science.gov (United States)

We have proposed and experimentally demonstrated an ultrafast optical pulse repetition rate multiplication technique from a relatively slow optical pulse source at 1550nm based on reconfigurable time domain spectral amplitude/phase filtering operation. In the proposed technique, a pair of dispersive fibers and a high speed electro-optical modulator driven by a 40GHz pulse pattern generator that can be rapidly programmed are used to control the repetition rate. In the experiment, repetition rate multiplication from 10GHz to a high speed repetition rate of 20GHz and 40GHz has been successfully achieved by the proposed time domain spectral amplitude/phase filtering.

Gao, Zhensen; Dai, Bo; Wang, Xu; Kataoka, Nobuyuki; Wada, Naoya

2010-12-01

418

ABJM amplitudes and the positive orthogonal Grassmannian  

Science.gov (United States)

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 thereof, 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 OG2 orthogonal Grassmannian to form a larger OG k , where 2 k 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 manifests the vanishing of consecutive minors as the singularity of all on-shell diagrams. Quite remarkably, for the BCFW recursion representation of the tree-level amplitudes, the on-shell diagram manifests the presence of all physical factorization poles, as well as the cancellation of the spurious poles. After analytically continuing the orthogonal Grassmannian to split signature, we reveal that each on-shell diagram in fact resides in the positive cell of the orthogonal Grassmannian, where all minors are positive. In this language, the amplitudes of ABJM theory is simply an integral of a product of d log forms, over the positive orthogonal Grassmannian.

Huang, Yu-tin; Wen, CongKao

2014-02-01

419

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

International Nuclear Information System (INIS)

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

1987-01-01

420

Injection coupling with high amplitude transverse modes: Experimentation and simulation  

Science.gov (United States)

High frequency combustion instabilities have technical importance in the design of liquid rocket engines. These phenomena involve a strong coupling between transverse acoustic modes and combustion. They are currently being investigated by combining experimentation and numerical simulations. On the experimental level, the coupling is examined in a model scale system featuring a multiple injector combustor (MIC) comprising five coaxial injectors fed with liquid oxygen and gaseous methane. This system is equipped with a novel VHAM actuator (Very High Amplitude Modulator) which comprises two nozzles and a rotating toothed wheel blocking the nozzles in an alternate fashion. This device was designed to obtain the highest possible levels of transverse oscillation in the MIC. After a brief review of the VHAM, this article reports cold flow experiments using this modulator. Velocity maps obtained under resonant conditions using the VHAM are examined at different instants during a cycle of oscillation. Experimental data are compared with numerical pressure and velocity fields obtained from an acoustic solver. The good agreement observed in the nozzle vicinity indicates that numerical simulations can be used to analyze the complex flow field generated by the VHAM. To cite this article: Y. Mery et al., C. R. Mecanique 337 (2009).

Mery, Yoann; Ducruix, Sébastien; Scouflaire, Philippe; Candel, Sébastien

2009-06-01

 
 
 
 
421

Solitary Alfven wave envelopes and the modulational instability  

Energy Technology Data Exchange (ETDEWEB)

The derivative nonlinear Schroedinger equation describes the modulational instability of circularly polarized dispersive Alfven wave envelopes. It also may be used to determine the properties of finite amplitude localized stationary wave envelopes. Such envelope solitons exist only in conditions of modulational stability. This leaves open the question of whether, and if so, how, the modulational instability produces envelope solitons. 12 refs.

Kennel, C.F.

1987-06-01

422

Crack propagation under variable amplitude loading  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Experience shows that a damage induced by a given cycle is dependent on the loading history. In this regard, the objective of this paper is to study and describe the phenomenology of the