WorldWideScience
1

Residual Amplitude Modulation in Interferometric Gravitational Wave Detectors  

CERN Document Server

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

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

2013-01-01

2

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

3

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

4

Dependence of residual amplitude noise in electro-optic phase modulators on the intensity distribution of the incident field  

International Nuclear Information System (INIS)

Our results demonstrate that photorefractive residual amplitude modulation (RAM) noise in electro-optic modulators (EOMs) can be reduced by modifying the incident beam intensity distribution. Here we report an order of magnitude reduction in RAM when beams with uniform intensity (flat-top) profiles, generated with an LCOS-SLM, are used instead of the usual fundamental Gaussian mode (TEM00). RAM arises from the photorefractive amplified scatter noise off the defects and impurities within the crystal. A reduction in RAM is observed with increasing intensity uniformity (flatness), which is attributed to a reduction in space charge field on the beam axis. The level of RAM reduction that can be achieved is physically limited by clipping at EOM apertures, with the observed results agreeing well with a simple model. These results are particularly important in applications where the reduction of residual amplitude modulation to 10?6 is essential. (paper)

5

Analysis of frequency noise in ultra-stable optical oscillators with active control of residual amplitude modulation  

Science.gov (United States)

Two 1,064-nm Nd:YAG lasers frequency stabilized by high-finesse optical cavities are developed to investigate various noise mechanisms in ultra-stable optical oscillators. Active control of residual amplitude modulation using a separate sensing path is implemented and its effectiveness in the presence of a resonant optical cavity is theoretically analyzed and experimentally verified by measuring the rejection ratios in optical heterodyne beat between a perturbed laser and a stable reference. Laser frequency noises originated from vibration, residual amplitude modulation, quantum-limited shot noise, and electronic noise are experimentally analyzed. With active control, residual amplitude modulation is suppressed to below 1 × 10-6 at 0.02-1,000 s, reaching a minimum of 2 × 10-7 at ~2 s. A frequency stability of 2 × 10-15 is obtained from 0.1 to 10 s, and the optical heterodyne beat of the two Nd:YAG lasers shows 1-Hz linewidth with a measurement time of 4.096 s. In addition, the experimentally determined linewidths agree well with the calculation according to a simplified relationship between the linewidth and the underlying flicker noise that modulates the laser frequency.

Li, Liufeng; Shen, Hui; Bi, Jin; Wang, Chun; Lv, Shasha; Chen, Lisheng

2014-12-01

6

The amplitude modulation transform  

OpenAIRE

Motivated by the study of the local extrema of sin(x)/x we define the \\emph{Amplitude Modulation} transform of functions defined on (subsets of) the real line. We discuss certain properties of this transform and invert it in some easy cases.

Rivin, Igor

2002-01-01

7

LEARNING MODULE FOR QUADRATURE AMPLITUDE MODULATION  

OpenAIRE

We will study signal modulation in telecommunication systems in this diploma. There are several types of modulations, which are used for specific purposes, like phase, amplitude, and frequency modulations. We use modulations for adaptation of different signals to different transmissible signals. Moreover, modulations enable noise reduction and interferences, selection of transmission channel on the same data carrier, multiplexing and capacity increase of devices. Digital modulations differ fr...

Petrovic?, Primoz?

2012-01-01

8

Alternating-phase focusing with amplitude modulation  

International Nuclear Information System (INIS)

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

9

Alternating-phase focusing with amplitude modulation  

International Nuclear Information System (INIS)

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

10

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; Raufer, Stefan

2013-01-01

11

Amplitude modulation of wind turbine noise  

CERN Document Server

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

Makarewicz, Rufin

2013-01-01

12

Modulated convection at high frequencies and large modulation amplitudes  

International Nuclear Information System (INIS)

Modulated Rayleigh-Benard convection is analyzed for high frequencies and large modulation amplitudes. The linear theory of Gershuni and Zhukhovitskii is generalized to the nonlinear domain, and a subcritical bifurcation to convection is found in agreement with the experiments of Niemela and Donnelly. The crossover between the high-frequency (''Stokes layer'') regime and the low-frequency regime studied previously is analyzed

13

Amplitude modulation of wind turbine noise  

OpenAIRE

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 ...

Makarewicz, Rufin; Golebiewski, Roman

2013-01-01

14

Amplitude-modulated fiber-ring laser  

DEFF Research Database (Denmark)

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

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

2000-01-01

15

Modulator-free quadrature amplitude modulation signal synthesis  

Science.gov (United States)

The ability to generate high-speed on–off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5?Gbit?s?1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on–off-keyed 10?Gbit?s?1 systems and is absolutely prohibitive for today’s (>)100?Gbit?s?1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions.

Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O’Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan

2014-12-01

16

Modulator-free quadrature amplitude modulation signal synthesis.  

Science.gov (United States)

The ability to generate high-speed on-off-keyed telecommunication signals by directly modulating a semiconductor laser's drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5?Gbit?s(-1)-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on-off-keyed 10?Gbit?s(-1) systems and is absolutely prohibitive for today's (>)100?Gbit?s(-1) coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions. PMID:25523757

Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O'Carroll, John; Phelan, Richard; Richardson, David J; Slavík, Radan

2014-01-01

17

Factorization of residues of off-shell string amplitudes  

International Nuclear Information System (INIS)

All normalization factors are supplied for the calculation of off-shell string amplitudes in the formalism of Cohen et al. Wave function normalization constants are determined from the residues of poles in the two-point function. For amplitudes with one or two strings off-shell and an arbitrary number of on-shell particles, the residue of a pole in an off-shell channel factorizes into the product of the square root of the wave function normalization constant and the correctly normalized amplitude with the particle in the relevant channel on-shell. Factorization requires the same relation between the coupling constant defined by the topological term in the action and the coupling constant appearing in vertex operators that was derived previously from unitarity of S-matrix elements. (orig.)

18

Temporal dynamics of sinusoidal and non-sinusoidal amplitude modulation.  

Science.gov (United States)

Previous behavioural studies in human subjects have demonstrated the importance of amplitude modulations to the process of intelligible speech perception. In functional neuroimaging studies of amplitude modulation processing, the inherent assumption is that all sounds are decomposed into simple building blocks, i.e. sinusoidal modulations. The encoding of complex and dynamic stimuli is often modelled to be the linear addition of a number of sinusoidal modulations and so, by investigating the response of the cortex to sinusoidal modulation, an experimenter can probe the same mechanisms used to encode speech. The experiment described in this paper used magnetoencephalography to measure the auditory steady-state response produced by six sounds, all modulated in amplitude at the same frequency but which formed a continuum from sinusoidal to pulsatile modulation. Analysis of the evoked response shows that the magnitude of the envelope-following response is highly non-linear, with sinusoidal amplitude modulation producing the weakest steady-state response. Conversely, the phase of the steady-state response was related to the shape of the modulation waveform, with the sinusoidal amplitude modulation producing the shortest latency relative to the other stimuli. It is shown that a point in auditory cortex produces a strong envelope following response to all stimuli on the continuum, but the timing of this response is related to the shape of the modulation waveform. The results suggest that steady-state response characteristics are determined by features of the waveform outside of the modulation domain and that the use of purely sinusoidal amplitude modulations may be misleading, especially in the context of speech encoding. PMID:21039961

Prendergast, Garreth; Johnson, Sam R; Green, Gary G R

2010-11-01

19

Multilevel phase and amplitude modulation method for holographic memories with programmable phase modulator  

Science.gov (United States)

The utilization of spatial quadrature amplitude modulation (SQAM) signals with amplitude and phase modulation is a simple method used to improve storage capacity in a holographic data storage system. We propose a multilevel phase and amplitude modulation method for holographic memories with a programmable phase modulator (PPM). In this method, holographic page data is recorded by a two-step exposure process for different phase-modulated data. There is no need to adjust the positions of spatial light modulators (SLM) with high accuracy because we use only one spatial modulator. We estimate the quality of 16 SQAM signals produced by our technique.

Honma, Satoshi; Sekiguchi, Toru

2014-09-01

20

Mechanisms of amplitude modulation in wind turbine noise  

OpenAIRE

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

21

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

22

Log-Likelihood Classification Of Quadrature Amplitude Modulation  

OpenAIRE

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

Savita Kamboj; Sonika Soni

2013-01-01

23

Amplitude modulation of frication noise by voicing saturates  

OpenAIRE

The two distinct sound sources comprising voiced frication, voicing and frication, interact. One effect is that the periodic source at the glottis modulates the amplitude of the frication source originating in the vocal tract above the constriction. Voicing strength and modulation depth for frication noise were measured for sustained English voiced fricatives using high-pass filtering, spectral analysis in the modulation (envelope) domain, and a variable pitch compensation procedure. Results ...

Pincas, J.; Jackson, Pjb

2005-01-01

24

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

25

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

Science.gov (United States)

Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a low-complexity modulator based on a semiconductor optical amplifier and electroabsorption modulator. Flexible amplitude/phase format transmission is achieved. The applicability of octary QAM for coherent optical access networks with sustainable 3 Gb/s per-user bandwidth is investigated for a long reach of 100 km, and its compatibility with a potentially high split is verified. PMID:22859139

Schrenk, Bernhard; Dris, Stefanos; Bakopoulos, Paraskevas; Lazarou, Ioannis; Voigt, Karsten; Zimmermann, Lars; Avramopoulos, Hercules

2012-08-01

26

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

27

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

28

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

29

Cantilever dynamics in amplitude modulation AFM: continuous and discontinuous transitions  

Science.gov (United States)

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

Santos, Sergio; Barcons, Victor; Font, Josep; Thomson, Neil H.

2010-07-01

30

About the Phasor Pathways in Analogical Amplitude Modulation  

CERN Document Server

The Phasor diagrams have long been used in Physics and Engineering. In telecommunications, this is particularly useful to clarify how the modulations work. This paper addresses rotating phasor pathways derived from different standard Amplitude Modulation Systems (e.g. A3E, H3E, J3E, C3F). A cornucopia of algebraic curves is then derived assuming a single tone or a double tone modulation signal. The ratio of the frequency of the tone modulator (fm) and carrier frequency (fc) is considered in two distinct cases, namely: fm/fc=1. The geometric figures are some sort of Lissajours figures. Different shapes appear looking like epicycloids (including cardioids), rhodonea curves, Lemniscates, folium of Descartes or Lam\\'e curves. The role played by the modulation index is elucidated in each case.

de Oliveira, H M

2015-01-01

31

Amplitude modulated drift wave packets in a nonuniform magnetoplasma  

Energy Technology Data Exchange (ETDEWEB)

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 Schrödinger 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 0modulated drift wave packet can propagate in the form of bright and dark envelope solitons or as a drift wave rogon.

Shukla, P.K., E-mail: profshukla@yahoo.de [International Centre for Advanced Studies in Physical Sciences and Institute for Theoretical Physics, Faculty of Physics and Astronomy, Ruhr University Bochum, D-447 80 Bochum (Germany); Misra, A.P., E-mail: apmisra@gmail.com [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan 731 235 (India)

2012-08-06

32

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

33

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

OpenAIRE

We report on the analysis and prototype-characterization of a dual-electrode electro-optic modulator that can generate both amplitude and phase modulations with a selectable relative phase, termed a universally tunable modulator (UTM). All modulation states can be reached by tuning only the electrical inputs, facilitating real-time tuning, and the device is shown to have good suppression and stability properties. A mathematical analysis is presented, including the developmen...

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

2003-01-01

34

Oblique amplitude modulation of dust-acoustic plasma waves  

OpenAIRE

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

Kourakis, I.; Shukla, P. K.

2004-01-01

35

Self-modulation of large amplitude Langmuir waves  

International Nuclear Information System (INIS)

We analyse the self-modulation of large amplitude Langmuir waves due to weak relativistic corrections to the plasma frequency and also to the nonlinear coupling of the wave with ion quasi-modes. It is shown that the wave is unstable to long wavelength perturbations with the instability occurring in the kinetic regime which is different to the quasi-static or hydrodynamic regimes. (author)

36

Amplitude modulation of atomic wave functions. Final report  

International Nuclear Information System (INIS)

The major theoretical advance has been to show that one can modulate Rydberg wave functions using either of two methods: (1) the amplitude modulation technique which depends on autoionization to deplete part of the wave function, or (2) a phase modulation method, which uses a change in the core potential to create a localized phase shift in the wave function. Essentially, these two methods can both be seen as using the core potential to change the Rydberg wave function, using the imaginary part of the potential to do amplitude modulation, or using the real part of the potential to do phase modulation. This work will be published as the authors acquire experimental results which show the differences between the two methods. One of the results of this theoretical study is that the initial proposal to study Barium 6snd states had a significant flaw. Neither the autoionization time, nor the quantum defect shifts are very large in these cases. This means that the modulation is relatively small. This shows itself primarily in the difficulty of seeing significant population redistribution into different 6snd states. The authors intend to correct this in the next funding cycle either: (a) by using the more quickly decaying Ba 6pnf states to modulate 6snd states, or (b) by using Sr 5 snd states, as outlined in this report. Their first, low power experiments are complete. These experiments have used two pulses to do a temporal version of the Ramsey separated oscillatory fields excitation. The two pulses are generated by passing the single pulse through a Michelson-Morley interferometer, which is computer controlled to sweep one arm through 2.5 microm in steps of 10 nm. The second pulse's excitation interferes with that of the first pulse, and so the total excitation has a sinusoidal variation (with a time period equal to the optical period) on top of a constant background. The amplitude of the total variation should decay at half of the rate decay rate of the autoionizing state, so this produces a time-resolved measurement of the very rapid autoionization decay. Although this does not yet show that the atom stores modulations in the bound coherent state, it does demonstrate that the atom can be excited to an autoionizing state with high efficiency, and then brought back to a bound state at a later time. The second set of experiments takes the previous work to the strong coupling regime

37

Remotely powered and controlled EAPap actuator by amplitude modulated microwaves  

International Nuclear Information System (INIS)

This paper reports on a remotely powered and controlled Electro-Active Paper (EAPap) actuator without onboard controller using amplitude modulated microwaves. A rectenna is a key element for microwave power transmission that converts microwaves into dc power through coupling and rectification. In this study, the concept of a remotely controlled and powered EAPap actuator is proposed by means of modulating microwaves with a control signal and demodulating it through the rectenna rectification. This concept is applied to a robust EAPap actuator, namely cellulose–polypyrrole–ionic liquid (CPIL) EAPap. Details of fabrication and characterization of the rectenna and the CPIL-EAPap actuator are explained. Also, the charge accumulation problem of the actuator is explained and resolved by connecting an additional resistor. Since this idea can eliminate the onboard controller by supplying the operating signal through modulation, a compact and lightweight actuator can be achieved, which is useful for biomimetic robots and remotely driven actuators. (technical note)

38

Quantifying the distortion products generated by amplitude-modulated noise.  

Science.gov (United States)

When sinusoidal amplitude modulation (SAM) is applied to noise or tone carriers, the stimuli can generate audible distortion products in the region of the modulation frequency. As a result, when bandpass-filtered SAM noise is used to investigate temporal processing, a band of unmodulated noise is typically positioned at the modulation frequency to mask any distortion products. This study was designed to investigate the distortion products for bandpass noise carriers, and so reduce ambiguity about the form of this distortion and its role in perception. The distortion consists of two distortion-noise bands and a distortion tone at the modulation frequency. In the first two experiments, the level and phase of the distortion tone are measured using two different experimental paradigms. In the third experiment, modulation-frequency difference limens are measured for filtered SAM noise and it is shown that performance deteriorates markedly when the distortion tone is canceled. In a fourth experiment, masked threshold is measured at low frequencies for bands of high-frequency, unmodulated noise with the same levels and spectra as the SAM noises in the earlier experiments. The results confirm that unmodulated noise also produces quadratic distortion which may explain some aspects of earlier reports on remote masking. PMID:10573887

Wiegrebe, L; Patterson, R D

1999-11-01

39

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

40

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

41

Dispersion interferometer using modulation amplitudes on LHD (invited)  

International Nuclear Information System (INIS)

Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 1017 m?3 is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 1020 m?3 can be overcome by a sufficient sampling rate of about 100 kHz

42

Dispersion interferometer using modulation amplitudes on LHD (invited)  

Energy Technology Data Exchange (ETDEWEB)

Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup ?3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup ?3} can be overcome by a sufficient sampling rate of about 100 kHz.

Akiyama, T., E-mail: takiyama@lhd.nifs.ac.jp; Yasuhara, R.; Kawahata, K. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292 (Japan); Okajima, S.; Nakayama, K. [Chubu University, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan)

2014-11-15

43

Dispersion interferometer using modulation amplitudes on LHD (invited)a)  

Science.gov (United States)

Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 1017 m-3 is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 1020 m-3 can be overcome by a sufficient sampling rate of about 100 kHz.

Akiyama, T.; Yasuhara, R.; Kawahata, K.; Okajima, S.; Nakayama, K.

2014-11-01

44

Research proposal on : amplitude modulated reflectometry system for JET divertor  

International Nuclear Information System (INIS)

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

45

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

46

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.

2004-06-01

47

Dependence of critical current and fields of periodically modulated superconducting alloys on modulation amplitude  

International Nuclear Information System (INIS)

The critical current Jsub(c)(Hsub(||)) of superconducting alloy films with a modulation of composition across thickness is shown to be a sensitive function of the periodic heterogeneity when the period is of the order of magnitude of the characteristic length scales xi(T), lambda(T) of the vortex. (A magnetic field Hsub(||) is applied along the layers so that the Lorentz force is exerted a long the direction of modulation). We stress in particular that it is a more sensitive function than critical fields which hardly depend on the amplitude of modulation. (orig.)

48

Stream Segregation in the Perception of Sinusoidally Amplitude-Modulated Tones  

OpenAIRE

Amplitude modulation can serve as a cue for segregating streams of sounds from different sources. Here we evaluate stream segregation in humans using ABA- sequences of sinusoidally amplitude modulated (SAM) tones. A and B represent SAM tones with the same carrier frequency (1000, 4000 Hz) and modulation depth (30, 100%). The modulation frequency of the A signals (fmodA) was 30, 100 or 300 Hz, respectively. The modulation frequency of the B signals was up to four octaves higher (?fmod). Three...

Dollez?al, Lena-vanessa; Beutelmann, Rainer; Klump, Georg M.

2012-01-01

49

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

International Nuclear Information System (INIS)

During propagating in Nd-glass amplifiers, the spectra of the broadband laser pulses are modulated due to gain narrowing and gain saturation effects, resulting in loss of sidebands and unbalance of the spectra, and further leading to the temporal intensity modulation. The amplitude modulations (AMs) have been numerically simulated for different broadband laser sources. The effects of the gain bandwidth, the laser bandwidth, as well as the deviation of central wavelength between the laser source and amplifier of the AMs have been analyzed. Results indicate that all of the different broadband laser sources discussed in this paper exhibit more or less AMs, and the temporal intensity modulation of stacked chirped pulses is smaller than that of sinusoidally frequency-modulated pulses. (authors)

50

External and internal limitations in amplitude-modulation processing  

DEFF Research Database (Denmark)

Three experiments are presented to explore the relative role of "external" signal variability and "internal" resolution limitations of the auditory system in the detection and discrimination of amplitude modulations (AM). In the first experiment, AM-depth discrimination performance was determined using sinusoidally modulated broadband-noise and pure-tone carriers. The AM index, m, of the standard ranged from -28 to -3 dB (expressed as 20 log m). AM-depth discrimination thresholds were found to be a fraction of the AM depth of the standard for standards down to -18 dB, in the case of the pure-tone carrier, and down to -8 dB, in the case of the broadband-noise carrier. For smaller standards, AM-depth discrimination required a fixed increase in AM depth, independent of the AM depth of the standard. In the second experiment, AM-detection thresholds were obtained for signal-modulation frequencies of 4, 16, 64, and 256 Hz, applied to either a band-limited random-noise carrier or a deterministic ("frozen") noise carrier, as a function of carrier bandwidth (8 to 2048 Hz). In general, detection thresholds were higher for the random- than for the frozen-noise carriers. For both carrier types, thresholds followed the pattern expected from frequency-selective processing of the stimulus envelope. The third experiment investigated AM masking at 4, 16, and 64 Hz in the presence of a narrow-band masker modulation. The variability of the masker was changed from entirely frozen to entirely random, while the long-term average envelope power spectrum was held constant. The experiment examined the validity of a long-term average quantity as the decision variable, and the role of memory in experiments with frozen-noise maskers. The empirical results were compared to predictions obtained with two modulation-filterbank models. The predictions revealed that AM-depth discrimination and AM detection are limited by a combination of the external signal variability and an internal "Weber-fraction" noise process.

Ewert, Stephan; Dau, Torsten

2004-01-01

51

An amplitude-phase approach to calculating Regge-pole positions and residues  

Energy Technology Data Exchange (ETDEWEB)

New amplitude-phase formulae for Regge-pole positions and residues are derived. The derivation makes use of certain invariants of the Ermakov-Lewis type. The formulas allow calculation to be made on the real r-axis, with an additional flexibility to optimize its numerical aspects.

Thylwe, Karl-Erik [KTH-Mechanics, Royal Institute of Technology, S-100 44 Stockholm (Sweden); Sokolovski, Dmitri [Department of Applied Mathematics, Queen' s University, Belfast, BT7 1NN (United Kingdom)

2005-06-10

52

Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes  

OpenAIRE

In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. W...

Ma, Zong-min; Mu, Ji-liang; Tang, Jun; Xue, Hui; Zhang, Huan; Xue, Chen-yang; Liu, Jun; Li, Yan-jun

2013-01-01

53

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

OpenAIRE

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 n...

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

2009-01-01

54

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

Science.gov (United States)

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

Lavenex, P B

1999-07-01

55

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.

2002-06-01

56

Residual fatigue life estimation using a nonlinear ultrasound modulation method  

Science.gov (United States)

Predicting the residual fatigue life of a material is not a simple task and requires the development and association of many variables that as standalone tasks can be difficult to determine. This work develops a modulated nonlinear elastic wave spectroscopy method for the evaluation of a metallic components residual fatigue life. An aluminium specimen (AA6082-T6) was tested at predetermined fatigue stages throughout its fatigue life using a dual-frequency ultrasound method. A modulated nonlinear parameter was derived, which described the relationship between the generation of modulated (sideband) responses of a dual frequency signal and the linear response. The sideband generation from the dual frequency (two signal output system) was shown to increase as the residual fatigue life decreased, and as a standalone measurement method it can be used to show an increase in a materials damage. A baseline-free method was developed by linking a theoretical model, obtained by combining the Paris law and the Nazarov–Sutin crack equation, to experimental nonlinear modulation measurements. The results showed good correlation between the derived theoretical model and the modulated nonlinear parameter, allowing for baseline-free material residual fatigue life estimation. Advantages and disadvantages of these methods are discussed, as well as presenting further methods that would lead to increased accuracy of residual fatigue life detection.

Piero Malfense Fierro, Gian; Meo, Michele

2015-02-01

57

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

58

Effects of stimulus duration on amplitude modulation processing with cochlear implants  

OpenAIRE

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...

Luo, Xin; Galvin, John J.; Fu, Qian-jie

2010-01-01

59

Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes.  

Science.gov (United States)

In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. We also compared the corrugations in the local contact potential difference on the surface of Ge (001), which shows atomic resolution in heterodyne AM-KPFM. In contrast, atomic resolution cannot be obtained in FM-KPFM under the same experimental conditions. The higher potential resolution in heterodyne AM-KPFM was attributed to the lower crosstalk and higher potential sensitivity between topographic and potential measurements. PMID:24350866

Ma, Zong-Min; Mu, Ji-Liang; Tang, Jun; Xue, Hui; Zhang, Huan; Xue, Chen-Yang; Liu, Jun; Li, Yan-Jun

2013-01-01

60

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

International Nuclear Information System (INIS)

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

61

Analyses of the mechanisms of amplitude modulation of aero-acoustic wind turbine sound  

DEFF Research Database (Denmark)

This paper explores the source mechanism which cause amplitude modulation of the emitted sound of a wind turbine at large distances from the turbine, named as other amplitude modulation. Measurements of the fluctuating surface pressure on a 2.3MW wind turbine showed a considerable variation over a blade revolution in the presence of angle of attack variations. If the blade undergoes transient stall, the variation of the surface pressure spectrum was enhanced and shifted to frequencies below 200Hz. The surface pressure spectra could be directly related to the emitted far eld sound. These ndings give further evidence that transient stall is a main mechanism to cause other amplitude modulation. Wind shear was identified as a critical condition to cause angle of attack variations. Dierent control strategies to mitigate other amplitude modulation were proposed.

Fischer, Andreas; Aagaard Madsen, Helge

2014-01-01

62

Slow Light of an Amplitude Modulated Gaussian Pulse in Cesium Vapor  

OpenAIRE

Slow light of an amplitude modulated Gaussian (AMG) pulse in cesium vapor is demonstrated and studied, as an appropriate amplitude modulation to a single pulse can expand its spectrum and thus increase the utilization efficiency of the bandwidth of a slow light system. In a single-$\\Lambda$ type electromagnetically induced transparency (EIT) system, the slowed AMG pulse experiences severe distortion, mainly owing to the frequency dependent transmission of medium. Additionall...

Tang, Wenzhuo; Luo, Bin; Liu, Yu; Guo, Hong

2009-01-01

63

Ten gigabits per second 16-level quadrature amplitude modulated millimeter-wave carrier generation using dual-drive Mach-Zehnder modulators incorporated photonic-vector modulator.  

Science.gov (United States)

A novel photonic-vector modulator architecture for the generation of 16 quadrature amplitude modulation (16 QAM) millimeter-wave carriers using dual-drive Mach-Zehnder modulators is proposed. Experimental generation of 5 Gbits/s 4 amplitude shift-keying (4 ASK) and 10 Gbits/s 16 QAM modulated 42 GHz carriers is reported. The multilevel modulated millimeter-wave signals are demodulated using an electrical receiver and its error-vector magnitude (EVM) estimated from the measurements, obtaining EVMs of -21.04 and -18.33 dB for 4 ASK and 16 QAM modulation formats, respectively. PMID:18709104

Sambaraju, Rakesh; Polo, Valentín; Corral, Juan Luis; Martí, Javier

2008-08-15

64

Correlation with a spatial light modulator having phase and amplitude cross coupling  

Science.gov (United States)

In correlation filtering a spatial light modulators is traditionally modeled as affecting only the phase or only the amplitude of light. Usually, however, a single operating parameter affects both phase and amplitude. An integral constraint is developed that is a necessary condition for optimizing a correlation filter having single parameter coupling between phase and amplitude. The phase-only filter is shown to be a special case.

Juday, Richard D.

1989-01-01

65

Analysis of amplitude modulation atomic force microscopy in aqueous salt solutions  

Science.gov (United States)

We present a numerical analysis of amplitude modulation atomic force microscopy in aqueous salt solutions, by considering the interaction of the microscope tip with a model sample surface consisting of a hard substrate and soft biological material through Hertz and electrostatic double layer forces. Despite the significant improvements reported in the literature concerning contact-mode atomic force microscopy measurements of biological material due to electrostatic interactions in aqueous solutions, our results reveal that only modest gains of ?15% in imaging contrast at high amplitude setpoints are expected under typical experimental conditions for amplitude modulation atomic force microscopy, together with relatively unaffected sample indentation and maximum tip-sample interaction values.

Karayaylal?, P?nar; Baykara, Mehmet Z.

2014-11-01

66

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

Science.gov (United States)

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

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

2014-06-01

67

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

OpenAIRE

This paper presents a new method to extend the linearity of the sinusoidal pulse width modulation (SPWM) to full range of the pulse dropping region. The proposed amplitude modulated triangular carrier PWM method (AMTCPWM) increases the dynamic range of the SPWM control and eliminates the need of nonlinear modulation in the pulse dropping region to reach the square wave boundary. The novel method combines the spectral quality of SPWM with the efficient single-mode linear control. A simple anal...

Ramkumar Subburam; Jeevananthan Seenithangam; Kamaraj Vijayarajan

2009-01-01

68

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

Science.gov (United States)

The effect of temporal asymmetry on amplitude modulation detection was studied using sawtooth modulators with rising (ramped) or falling (damped) temporal envelopes within each period of modulation. For pure-tone carriers, damped modulation was more detectable than ramped modulation for a 5-kHz carrier (by a threshold difference of 3.2 dB on average) but not for a 1-kHz carrier. The threshold difference obtained at 5 kHz between the ramped and damped modulators was consistent across modulation rates (8-128 Hz). This carrier frequency dependence suggests that the effect of temporally asymmetry on modulation detection originates from envelope-based, within-channel mechanisms. PMID:22087889

Shen, Yi; Lentz, Jennifer J

2011-11-01

69

Detection of frequency modulation by hearing-impaired listeners: Effects of carrier frequency, modulation rate, and added amplitude modulation  

Science.gov (United States)

It has been proposed that the detection of frequency modulation (FM) of sinusoidal carriers can be mediated by two mechanisms: a place mechanism based on FM-induced amplitude modulation (AM) in the excitation pattern, and a temporal mechanism based on phase-locking in the auditory nerve. The temporal mechanism appears to be ``sluggish'' and does not play a role for FM rates above about 10 Hz. It also does not play a role for high carrier frequencies (above about 5 kHz). This experiment examined FM detection in three young subjects with normal hearing and four elderly subjects with cochlear hearing loss. Carrier frequencies were 0.25, 0.5, 1, 2, 4, and 6 kHz and modulation rates were 2, 5, 10, and 20 Hz. FM detection thresholds were measured both in the absence of AM, and with AM of a fixed depth (m=0.33) added in both intervals of a forced-choice trial. The added AM was intended to disrupt cues based on FM-induced AM in the excitation pattern. Generally, the hearing-impaired subjects performed markedly more poorly than the normal-hearing subjects. For the normal-hearing subjects, the disruptive effect of the AM tended to increase with increasing modulation rate, for carrier frequencies below 6 kHz, as found previously by Moore and Sek [J. Acoust. Soc. Am. 100, 2320-2331 (1996)]. For the hearing-impaired subjects, the disruptive effective of the AM was generally larger than for the normal-hearing subjects, and the magnitude of the disruption did not consistently increase with increasing modulation rate. The results suggest that cochlear hearing impairment adversely affects both temporal and excitation pattern mechanisms of FM detection.

Moore, Brian C. J.; Skrodzka, Ewa

2002-01-01

70

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

71

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

72

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

73

Measurement of the amplitude and phase transfer functions of an optical modulator using a heterodyne technique  

OpenAIRE

We present a new technique that measures the full amplitude and phase transfer curves of the modulator as a function of the applied bias, from which the small signal ?-parameter can be calculated. The technique measures the amplitude and phase transfer functions simultaneously and directly, compared to techniques where a time-consuming data analysis is necessary to calculate the a-parameter and an additional measurement is necessary to estimate the phase. Additionally, the chirp profile for ...

Romstad, Francis Pascal; Birkedal, Dan; Mørk, Jesper; Hvam, Jørn Ma?rcher

2006-01-01

74

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-05-01

75

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

76

Pulsational Frequency and Amplitude Modulation in the $\\delta$\\,Sct star KIC\\,7106205  

CERN Document Server

Analysis of the \\textit{Kepler} $\\delta$\\,Sct star KIC\\,7106205 showed amplitude modulation in a single pressure mode, whilst all other pressure and gravity modes remained stable in amplitude and phase over the 1470\\,d length of the dataset. The \\textit{Kepler} dataset was divided into a series with time bins of equal length for which consecutive Fourier transforms were calculated. An optimum fixed frequency, calculated from a least-squares fit of all data, allowed amplitude and phase of each pulsation mode for each time bin to be tracked. The single pressure mode at $\

Bowman, Dominic M

2014-01-01

77

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

78

Heterodyne technique for measuring the amplitude and phase transfer functions of an optical modulator  

OpenAIRE

In this letter, we propose a technique based on heterodyne detection for accurately and simultaneously measuring the amplitude and phase transfer functions of an optical modulator. The technique is used to characterize an InGaAsp multiple quantum-well electroabsorption modulator. From the measurements we derive the small-signal alpha-parameter and the time-dependent chirp for different operation conditions.

Romstad, Francis Pascal; Birkedal, Dan; Mørk, Jesper; Hvam, Jørn Ma?rcher

2006-01-01

79

Heterodyne technique for measuring the amplitude and phase transfer functions of an optical modulator  

DEFF Research Database (Denmark)

In this letter, we propose a technique based on heterodyne detection for accurately and simultaneously measuring the amplitude and phase transfer functions of an optical modulator. The technique is used to characterize an InGaAsp multiple quantum-well electroabsorption modulator. From the measurements we derive the small-signal alpha-parameter and the time-dependent chirp for different operation conditions.

Romstad, Francis Pascal; Birkedal, Dan

2002-01-01

80

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

Science.gov (United States)

In this paper, we numerically demonstrate the advantage of utilizing continuous amplitude and phase modulation in super-oscillation focusing lens design. Numerical results show that compared with simple binary amplitude modulation, continuous amplitude and phase modulation can greatly improve the super-oscillation focusing performance by increasing the central lobe intensity and the ratio of its energy to the total energy, reducing the sidelobe intensity, and substantially extending the field of view. Our study also reveals the role of phase distribution in reducing the spatial frequency bandwidth of the super-oscillation optical field on the focal plane. Based on continuous amplitude and binary phase modulation, a lens was designed with double layer metal slit array for wavelength of 4.6 µm. COMSOL is used to carry out the 2D simulation. The lens focal length is 40.18? and the focal spot FWHM is 0.308?. Two largest sidelobes are located right next to the central lobe with intensity about 40% of the central lobe intensity. Except for the two sidelobes, other sidelobes have intensity less than 25% of the central lobe intensity, which leads to a clear field of view on the whole focal plane. PMID:25321591

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

2014-09-01

81

Radar transponder operation with compensation for distortion due to amplitude modulation  

Science.gov (United States)

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

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

2011-01-04

82

Soliton self-modulation of the turbulence amplitude and plasma rotation  

CERN Document Server

The space-uniform amplitude envelope of the Ion Temperature Gradient driven turbulence is unstable to small perturbations and evolves to nonuniform, soliton-like modulated profiles. The induced poloidal asymmetry of the transport fluxes can generate spontaneous poloidal spin-up of the tokamak plasma.

Spineanu, F

2002-01-01

83

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

Science.gov (United States)

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

Bowman, Dominic M.; Kurtz, Donald W.

2014-10-01

84

Amplitude modulation of electron plasma oscillations in a dense electron-hole plasma  

International Nuclear Information System (INIS)

By using a quantum hydrodynamic model, the amplitude modulation of electron plasma oscillations (EPOs) in an unmagnetized dense electron-hole (e-h) quantum plasma is investigated. The standard reductive perturbation technique is used to derive one-dimensional nonlinear Schroedinger equation for the modulated EPO wave packet. The effects of the quantum diffraction, charged dust impurities and the effective e-h mass ratio on the propagation of linear dispersive EPOs, as well as on the modulational stability/instability of finite amplitude EPOs are examined. It is found that these parameters significantly affect the propagation of the EPOs as well as the nonlinear stability/instability domain of the wave vector, quite distinct from the classical and quantum electron-ion or electron-positron plasmas. The relevance of our investigation to semiconductor plasmas is discussed

85

Wavelength- and amplitude-modulated photoacoustics: comparison of simulated and measured spectra of higher harmonics.  

Science.gov (United States)

Photoacoustic (PA) spectra generated by current modulation of a distributed feedback diode laser (DFB-DL) were measured for the ammonia absorption line at 1.53 microm and calculated using absorption spectra taken from a database. The algorithm is based on a combined amplitude- and wavelength-modulation (AM-WM) scheme. The spectral characteristics of the DFB-DL were determined by comparing simulated spectra with Fourier transform infrared measurements. PA spectra were measured and simulated from the first to fourth harmonic and a variation of the modulation depth with modulation frequency was observed. It was found that combined AM-WM modulation may produce larger PA signals than separate AM or WM detection for the first harmonic. PMID:18493286

Angelmahr, M; Miklós, A; Hess, P

2008-05-20

86

Study of a novel amplitude-phase modulation IRZ-MSK in high-speed optical fiber transmission system  

Science.gov (United States)

In this paper, a novel amplitude-phase modulation format, inverse-return-to-zero minimum shift keying (IRZ-MSK), is proposed. A scheme to realize the IRZ-MSK is introduced, and especially a method of demodulating the phase branch is presented. The influence of different duty cycles on the performance of the IRZ-MSK is discussed. Numerical simulations and analysis are performed, and the comparison between the 70% IRZ-MSK and the NRZ-MSK is made. The phase branches of 70% IRZ-MSK and the NRZ-MSK almost have the same dispersion tolerance, and the amplitude branch of 70% IRZ-MSK has a better dispersion tolerance than that of the NRZ-MSK when the residual dispersion is larger than 1.9 ps/nm/km. For the nonlinear tolerance, the EOP of the IRZ-MSK phase branch and amplitude branch reduces 0.5 dB and 3.8 dB than those of the NRZ-MSK respectively, when the launch power is 4 mW and dispersion is completely compensated. Meanwhile, the BER curves of the NRZ-MSK and IRZ-MSK are also made. The results show that, our proposed IRZ-MSK can not only improve the spectral efficiency, but also greatly mitigate the dispersion and nonlinear effects.

Shang, Tao; Chen, Jianqiao; Yang, Yintang; Tian, Yu

2014-06-01

87

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.

88

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

KAUST Repository

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

Ghaffar, Farhan Abdul

2012-09-30

89

Binaural unmasking of the periodic component in the envelope of an amplitude-modulated signal  

Science.gov (United States)

A binaural unmasking of a tone component that is present in an amplitude-time noise envelope of a high-frequency signal is studied. The signal has the form of a sinusoidal carrier of frequency 2000 5000 Hz amplitude modulated by a low-frequency signal. The modulating function is a mixture of a 300-Hz tone (interaurally inphase or antiphase) and a dichotic masking noise within 0 400 Hz, this mixture being subjected to a half-wave linear rectification. The listener has to detect the rhythmic component in the modulating noise function. It is shown that, under the aforementioned conditions, the binaural difference in masking levels grows up to 25 dB with increasing carrier frequency but drastically decreases in the case of a masking of the low-frequency part of the basilar membrane in the vicinity of 300 Hz. The lateralization based on the interaural phase of a 100% amplitude modulation by a 300-Hz tone at a carrier frequency within 2000 to 5000 Hz also drastically decreases (in our experiments) when the low-frequency part of the basilar membrane is masked.

Telepnev, V. N.

2004-05-01

90

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

Directory of Open Access Journals (Sweden)

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

Rinaldo André Mezzarane

2014-03-01

91

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

OpenAIRE

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

92

Measurement of the amplitude and phase transfer functions of an optical modulator using a heterodyne technique  

DEFF Research Database (Denmark)

We present a new technique that measures the full amplitude and phase transfer curves of the modulator as a function of the applied bias, from which the small signal ?-parameter can be calculated. The technique measures the amplitude and phase transfer functions simultaneously and directly, compared to techniques where a time-consuming data analysis is necessary to calculate the a-parameter and an additional measurement is necessary to estimate the phase. Additionally, the chirp profile for all operation points can be calculated.

Romstad, Francis Pascal; Birkedal, Dan

2001-01-01

93

Anamorphic optical transformation of an amplitude spatial light modulator to a complex spatial light modulator with square pixels [invited].  

Science.gov (United States)

A method is proposed for the construction of a square pixel complex spatial light modulator (SLM) from a commercial oblong full-high-definition (full-HD) amplitude SLM using an anamorphic optical filter. In the proposed scheme, one half-band of the optical Fourier transform of the amplitude-only spatial light field is rejected in the optical Fourier plane and the other half-band is reformatted to be an effective complex SLM with square pixels. This has an advantage in the viewing window plane since the shape of the viewing window becomes square and more ideal for observers who watch the hologram contents through it. For optimal transformation, the amplitude computer generated hologram encoding scheme was developed. Mathematical modeling of the proposed system is described herein, and it was experimentally demonstrated that the effective complex SLM displays complex holographic three-dimensional images with a clear depth discrimination effect. PMID:25322122

Kim, Hwi; Hwang, Chi-Young; Kim, Kwang-Soo; Roh, Jinyoung; Moon, Woonchan; Kim, Sungmin; Lee, Beom-Ryoel; Oh, Seungtaik; Hahn, Joonku

2014-09-20

94

Stream segregation in the perception of sinusoidally amplitude-modulated tones.  

Science.gov (United States)

Amplitude modulation can serve as a cue for segregating streams of sounds from different sources. Here we evaluate stream segregation in humans using ABA- sequences of sinusoidally amplitude modulated (SAM) tones. A and B represent SAM tones with the same carrier frequency (1000, 4000 Hz) and modulation depth (30, 100%). The modulation frequency of the A signals (f(modA)) was 30, 100 or 300 Hz, respectively. The modulation frequency of the B signals was up to four octaves higher (?f(mod)). Three different ABA- tone patterns varying in tone duration and stimulus onset asynchrony were presented to evaluate the effect of forward suppression. Subjects indicated their 1- or 2-stream percept on a touch screen at the end of each ABA- sequence (presentation time 5 or 15 s). Tone pattern, f(modA), ?f(mod), carrier frequency, modulation depth and presentation time significantly affected the percentage of a 2-stream percept. The human psychophysical results are compared to responses of avian forebrain neurons evoked by different ABA- SAM tone conditions [1] that were broadly overlapping those of the present study. The neurons also showed significant effects of tone pattern and ?f(mod) that were comparable to effects observed in the present psychophysical study. Depending on the carrier frequency, modulation frequency, modulation depth and the width of the auditory filters, SAM tones may provide mainly temporal cues (sidebands fall within the range of the filter), spectral cues (sidebands fall outside the range of the filter) or possibly both. A computational model based on excitation pattern differences was used to predict the 50% threshold of 2-stream responses. In conditions for which the model predicts a considerably larger 50% threshold of 2-stream responses (i.e., larger ?f(mod) at threshold) than was observed, it is unlikely that spectral cues can provide an explanation of stream segregation by SAM. PMID:22984436

Dolležal, Lena-Vanessa; Beutelmann, Rainer; Klump, Georg M

2012-01-01

95

High potential sensitivity in heterodyne amplitude-modulation Kelvin probe force microscopy  

Science.gov (United States)

A surface potential measurement method using amplitude-modulation and heterodyne techniques is proposed. The effect of the stray capacitance between a cantilever and a sample in Kelvin probe force microscopy and the electrostatic force spectroscopy measurements are almost completely removed, because the distance (z) dependence of the modulated electrostatic force increases from 1/z to1/z2. This method improves the sensitivity of short range forces and reduces the surface potential measurement crosstalk that is induced by topographic feedback. This method has the advantage of high potential sensitivity due to the high cantilever Q value under vacuum. Quantitative surface potential measurements are demonstrated.

Sugawara, Yasuhiro; Kou, Lili; Ma, Zongmin; Kamijo, Takeshi; Naitoh, Yoshitaka; Jun Li, Yan

2012-05-01

96

Amplitude and phase modulation of radiation in a travelling-wave amplifier based on a laser diode  

International Nuclear Information System (INIS)

An analytical solution (in quadratures) to the problem of propagation of quasi-monochromatic optical signal in a semiconductor amplifier under harmonic modulation of its pump current is obtained for the first time. It is shown that the modulation of the output radiation has amplitude and phase features. The relation is found between the coefficients of the amplitude and phase modulation with the effect of gain saturation taken into account. Adequacy of the results obtained is confirmed experimentally. (control of laser radiation parameters)

97

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

Science.gov (United States)

Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit nonideal behavior. Here, we demonstrate that amplitude modulation can improve the performance of quantum-dot-based sources. Starting with a bright source consisting of a single quantum dot in a fiber-coupled microdisk cavity, we use synchronized amplitude modulation to temporally filter the emitted light. We observe that the single photon purity, temporal overlap between successive emission events, and indistinguishability can be greatly improved with this technique. As this method can be applied to any triggered single photon source, independent of geometry and after device fabrication, it is a flexible approach to improve the performance of systems based on single solid-state quantum emitters, which often suffer from excess dephasing and multi-photon background emission. PMID:23466520

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

2013-01-01

98

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

CERN Document Server

Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit non-ideal behavior. Here, we demonstrate that amplitude modulation can improve the performance of quantum-dot-based sources. Starting with a bright source consisting of a single quantum dot in a fiber-coupled microdisk cavity, we use synchronized amplitude modulation to temporally filter the emitted light. We observe that the single photon purity, temporal overlap between successive emission events, and indistinguishability can be greatly improved with this technique. As this method can be applied to any triggered single photon source, independent of geometry and after device fabrication, it is a flexible approach to improve the performance of solid-state systems, which often suffer from excess dephasing and multi-photon background emission.

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

2012-01-01

99

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

100

Arbitrary manipulation of spatial amplitude and phase using phase-only spatial light modulators  

Science.gov (United States)

Spatial structure of a light beam is an important degree of freedom to be extensively explored. By designing simple configurations with phase-only spatial light modulators (SLMs), we show the ability to arbitrarily manipulate the spatial full field information (i.e. amplitude and phase) of a light beam. Using this approach to facilitating arbitrary and independent control of spatial amplitude and phase, one can flexibly generate different special kinds of light beams for different specific applications. Multiple collinear orbital angular momentum (OAM) beams, Laguerre-Gaussian (LG) beams, and Bessel beams, having both spatial amplitude and phase distributions, are successfully generated in the experiments. Some arbitrary beams with odd-shaped intensity are also generated in the experiments. PMID:25501584

Zhu, Long; Wang, Jian

2014-01-01

101

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

102

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

CERN Document Server

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

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

2003-01-01

103

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

CERN Document Server

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

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

2001-01-01

104

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

OpenAIRE

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 ...

Santos, Sergio; Barcons, Victor; Verdaguer, A.; Chiesa, Matteo

2011-01-01

105

Slow light of an amplitude modulated Gaussian pulse in electromagnetically induced transparency medium  

OpenAIRE

The slow light effects of an amplitude modulated Gaussian (AMG) pulse in a cesium atomic vapor are presented. In a single-$\\Lambda$ type electromagnetically induced transparency (EIT) medium, more severe distortion is observed for an AMG pulse than a Gaussian one. Using Fourier spectrum analysis, we find that the distortion, as well as the loss, is dominantly caused by linear absorption than dispersion. Accordingly, a compensation method is proposed to reshape the slow light...

Tang, Wenzhuo; Luo, Bin; Liu, Yu; Guo, Hong

2009-01-01

106

Controlling the evolution of nondiffracting speckle by complex amplitude modulation on a phase-only spatial light modulator  

Science.gov (United States)

In this work we investigate the structure of nondiffracting speckle fields, both experimentally and theoretically. We are able to produce very good agreement between the experimentally recorded and theoretically calculated fields by using complex amplitude modulation on a phase-only spatial light modulator to implement controlled ring-slit experiments for the generation of nondiffracting speckle fields. The structure of the nondiffracting speckle due to binary and continuous phase modulations for both a uniform and a normal distribution is investigated. We find that we are able to engineer whether the nondiffracting field will appear as speckle or a structured zero-order Bessel beam by adjusting the standard deviation in the distribution. Having the ability to control where in the spectrum, from fully-developed nondiffracting speckle to a symmetric zero-order Bessel beam, the nondiffracting field will exist can prove to be a useful resource in the non-destructive testing of materials.

Dudley, Angela; Vasilyeu, Ruslan; Belyi, Vladimir; Khilo, Nikolai; Ropot, Piotr; Forbes, Andrew

2012-01-01

107

Cyclic pitch for the control of wind turbine noise amplitude modulation  

DEFF Research Database (Denmark)

Using experimental data acquired during a wind turbine measurement campaign, it is shown that amplitude modulation of aerodynamic noise can be generated by the rotating blades in conjunction with the atmospheric wind shear. As an attempt to alleviate this phenomenon, a control strategy is designed in form of a cyclic pitch of the blades. As a side effect, it is shown that it is also possible to reduce fatigue load on the blade using this cyclic pitch. The main goal is to reduce both amplitude modulation and fatigue load without compromising the energy harvested from the wind. A simulation tool that can model the different aerodynamic and aeroacoustic aspects of the study is presented. Parameters controlling the cyclic pitch are optimized in order to reduce amplitude modulation and/or fatigue load to a minimum. It is shown that such a minimum can be found and that benefit may be achieved if such a strategy is to be implemented on an actual wind turbine, though at the expense of an increased wear and tear of the pitch control system.

Bertagnolio, Franck; Aagaard Madsen, Helge

2014-01-01

108

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

Science.gov (United States)

The main goal of this study was to study the performance of fuzzy logic controllers combined with simplified hybrid amplitude/pulse-width (AM/PW) modulation to regulate muscle force via nerve electrical stimulation. The recruitment curves with AM/PW and AM modulations were constructed for the calf muscles of rabbits. Integrated with the modulation methods, a proportional-integral-derivative (PID) and three fuzzy logic controllers were designed and applied for the electrical stimulation of tibial nerves to control the ankle torque under isometric conditions. The performance of the two modulation methods combined with the four controllers was compared when the ankle was fixed at three positions for both in vivo experiments and model simulations using a nonlinear muscle model. For the animal experiments, AM/PW modulation performed better than AM modulation alone. The fuzzy PI controller performed marginally better and was resistant to external noises, though it tended to have a larger overshoot. The performance of the controllers had a similar trend in the three different joint positions, and the simulation results with the nonlinear model matched the experimental results well. In conclusion, AM/PW modulation improved controller performance, while the contribution of fuzzy logic was only marginal. PMID:22422279

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

2012-04-01

109

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

110

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

111

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

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new method to extend the linearity of the sinusoidal pulse width modulation (SPWM to full range of the pulse dropping region. The proposed amplitude modulated triangular carrier PWM method (AMTCPWM increases the dynamic range of the SPWM control and eliminates the need of nonlinear modulation in the pulse dropping region to reach the square wave boundary. The novel method combines the spectral quality of SPWM with the efficient single-mode linear control. A simple analytical characterization of the exact method is presented and its effectiveness is demonstrated using simulation for the basic single-phase H-bridge inverter circuit. The hardware results of the designed prototype inverter are presented to validate the betterment of the novel scheme. .

Ramkumar Subburam

2009-01-01

112

Amplitude modulation of hydromagnetic waves and associated rogue waves in magnetoplasmas.  

Science.gov (United States)

It is shown that the dynamics of amplitude-modulated compressional dispersive Alfvénic (CDA) waves in a collisional megnetoplasma is governed by a complex Ginzburg-Landau (CGL) equation. The nonlinear dispersion relation for the modulational instability of the CDA waves is derived and investigated numerically. It is found that the growth rate of the modulational instability decreases (increases) with the increase of the normalized electron-ion collision frequency ? (the plasma ?). The modulational instability criterion for the CGL equation is defined precisely and investigated numerically. The region of the modulational instability becomes narrower with the increase of ? and ?, indicating that the system dissipates the wave energy by collisions, and a stable CDA wave envelope packet in the form of a hole will be a dominant localized pulse. For a collisionless plasma, i.e., ?=0, the CGL equation reduces to the standard nonlinear Schrödinger (NLS) equation. The latter is used to investigate the modulational (in)stability region for the CDA waves in a collisionless magnetoplasma. It is shown that, within unstable regions, a random set of nonlinearly interacting CDA perturbations leads to the formation of CDA rogue waves. In order to demonstrate that the characteristics of the CDA rogue waves are influenced by the plasma ?, the relevant numerical analysis of the appropriate nonlinear solution of the NLS equation is presented. The application of our investigation to space and laboratory magnetoplasmas is discussed. PMID:23031035

Sabry, R; Moslem, W M; Shukla, P K

2012-09-01

113

Detection and identification of nonlinearities by amplitude and frequency modulation analysis  

Science.gov (United States)

This paper presents an amplitude and frequency modulation method (AFMM) for extracting characteristics of nonlinear systems and intermittent transient responses by processing stationary/transient responses using the empirical mode decomposition, Hilbert-Huang transform (HHT), and nonlinear dynamic characteristics derived from perturbation analysis. A sliding-window fitting (SWF) method is derived and used to show the physical implications of the proposed method and other methods for data processing and transformation. Similar to the wavelet transform, the SWF uses windowed regular harmonics and function orthogonality to extract time-localized regular and/or distorted harmonics, and then the amplitude and frequency modulations of the harmonics are used to identify system nonlinearities. On the other hand, the HHT uses the apparent time scales revealed by the signal's local maxima and minima and cubic splines of the extrema to sequentially sift components of different time scales, starting from high-frequency to low-frequency ones. Because HHT does not use predetermined basis functions and function orthogonality for component extraction, it provides more accurate instant amplitudes and frequencies of extracted components for accurate estimation of system characteristics and nonlinearities. Moreover, because the first component extracted by HHT contains all original discontinuities, its time-varying amplitude and frequency are excellent indicators for pinpointing times and locations of impulsive external loads. However, the discontinuity-induced Gibbs' phenomenon makes HHT analysis inaccurate around the two data ends. On the other hand, the SWF analysis is not affected by Gibbs' phenomenon, but it cannot extract accurate time-varying frequencies and amplitudes because of the use of predetermined basis functions, function orthogonality, and windowed curve fitting for component extraction. Numerical results show that the proposed AFMM can provide accurate estimation of softening and hardening effects, different orders of nonlinearity, linear and nonlinear system parameters, and time instants of intermittent transient responses.

Pai, P. Frank; Palazotto, Anthony N.

2008-07-01

114

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)

115

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

Science.gov (United States)

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

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

2013-10-01

116

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

117

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

Science.gov (United States)

The nonlinear properties of the amplitude-modulated circularly polarized Alfven wave are studied for beta less than one. 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.

Machida, S.; Spangler, S. R.; Goertz, C. K.

1987-01-01

118

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

Directory of Open Access Journals (Sweden)

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

Yunlong Yang

2013-01-01

119

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

Science.gov (United States)

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; Barcons, Victor; Verdaguer, Albert; Chiesa, Matteo

2011-12-01

120

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

International Nuclear Information System (INIS)

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

121

Age-Related Differences in Auditory Processing as Assessed by Amplitude-Modulation Following Responses in Quiet and in Noise  

OpenAIRE

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 you...

AravindakshanParthasarathy; PaulACunningham

2010-01-01

122

General analytic solution for far-field phase and amplitude control, with a phase-only spatial light modulator.  

OpenAIRE

We present an analytical solution for the phase introduced by a phase-only spatial light modulator to generate far-field phase and amplitude distributions within a domain of interest. The solution is demonstrated experimentally and shown to enable excellent control of the far-field amplitude and phase.

Liu, Lz; O Keeffe, K.; Lloyd, Dt; Hooker, Sm

2014-01-01

123

Perceptual interaction between carrier periodicity and amplitude modulation in broadband stimuli: A comparison of the autocorrelation and modulation-filterbank model  

OpenAIRE

Recent temporal models of pitch and amplitude modulation perception converge on a relatively realistic implementation of cochlear processing followed by a temporal analysis of periodicity. However, for modulation perception, a modulation filterbank is applied whereas for pitch perception, autocorrelation is applied. Considering the large overlap in pitch and modulation perception, this is not parsimonious. Two experiments are presented to investigate the interaction between carrier periodicit...

Stein, A.; Ewert, Stephan; Wiegrebe, L.

2005-01-01

124

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

125

Wind turbine amplitude modulation: research to improve understanding as to its cause & effect  

OpenAIRE

The issue of amplitude modulated noise (often referred to as ?blade swish? or ?AM?) arising from the operation of wind turbines is presently receiving a high focus of attention. Whilst the acceptability of audible noise from wind turbines continues to be the subject of considerable debate, the specific issue of AM has come to the fore in recent years. The issue of AM is not a new one, having been the subject of a previous study undertaken on behalf of the UK Government by the University o...

Cand, Matthew; Bullmore, Andrew; Smith, Malcom; Von-hunerbein, Sabine; Davis, Robert

2012-01-01

126

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)

127

Slow light of an amplitude modulated Gaussian pulse in electromagnetically induced transparency medium  

CERN Document Server

The slow light effects of an amplitude modulated Gaussian (AMG) pulse in a cesium atomic vapor are presented. In a single-$\\Lambda$ type electromagnetically induced transparency (EIT) medium, more severe distortion is observed for an AMG pulse than a Gaussian one. Using Fourier spectrum analysis, we find that the distortion, as well as the loss, is dominantly caused by linear absorption than dispersion. Accordingly, a compensation method is proposed to reshape the slow light pulse based on the transmission spectrum. In addition, we find a novel way to obtain simultaneous slow and fast light.

Tang, Wenzhuo; Liu, Yu; Guo, Hong

2009-01-01

128

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

OpenAIRE

High-speed downlink packet access (HSDPA) is a feature introduced to the universal mobile telecommunications system (UMTS) in 2002. It allows data rates of up to 14.4 Mbps in the downlink. In 2007 new features were standardized to HSDPA, including 64 Quadrature Amplitude Modulation (64-QAM). 64-QAM allows more data to be transmitted on the same bandwidth, increasing the HSDPA peak data rate to 21.6 Mbps. Transmitters and receivers must be updated with new algorithms to support this new ...

Pitka?nen, Sampo

2008-01-01

129

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

130

Large-area, three-state, binary amplitude and binary phase vertical-cavity multiple quantum well electroabsorption modulator.  

Science.gov (United States)

We present the design and characterization of a large optical modulator array based on GaAs multiple quantum wells for amplitude and phase modulation. The device shows two high-reflectance states with a phase difference close to 180 degrees for use as a binary phase modulator. It also shows a third, low-reflectance state for use as an amplitude modulator. It is segmented into 64 pixels in a single row, giving an active area of 2mm x 5mm. We discuss the device performance as a ternary binary amplitude and binary phase modulator, including contrast ratio and uniformity, and show that a voltage swing of only 5V is needed to drive it. PMID:19547190

Junique, Stéphane; Wang, Qin; Almqvist, Susanne; Noharet, Bertrand; Andersson, Jan Y

2007-07-01

131

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

132

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

Science.gov (United States)

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

Wang, Yang; Wang, Qianqian; Wang, Haiwei

2010-11-01

133

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 sources’ values along with the optimized switching angles. This paper proposes a new SHE-PWAM control strategy and its realization in a drive application. Analysis and simulations are carried out on a fivelevel CHB inverter. Experimental verifications also validate the simulation results. The results demonstrate that the new SHEPWAM technique improves the performance of the drive compared to the conventional SHE-PWM.

Ghoreishy, Hoda; Varjani, Ali Yazdian

2013-01-01

134

Effects of temporal properties on compound action potentials in response to amplitude-modulated electric pulse trains in guinea pigs.  

Science.gov (United States)

The electrically evoked compound action potential (ECAP) of the auditory nerve in response to amplitude-modulated pulse trains varies over time, but the response amplitudes are not linearly proportional to the level of stimulus pulses. At least two mechanisms could contribute to the deviations of the ECAP response pattern from that of the stimulus envelope. The first mechanism is time-invariant or stationary that reflects the non-linear growth of response amplitude with changes in stimulus level that is evident in the response to single pulses. This can be considered a time-invariant or stationary effect. The second mechanism is time-variant or non-stationary and reflects neural refractoriness and adaptation. The purpose of this study was to characterize the auditory nerve responses to amplitude-modulated pulse trains and also to evaluate the extent to which the stationary and non-stationary effects may contribute to those responses. ECAP amplitudes were predicted from single-pulse growth functions of the auditory nerve to account for time-invariant effects. Linear regression was performed on the measured vs. predicted ECAP amplitudes to quantify the discrepancies between the two datasets, thereby separating the influence of non-linear growth from time-varying effects on ECAP amplitudes. The results demonstrated a bandpass function of the modulated response amplitudes, with a low-cutoff modulation frequency at 300Hz and a high-cutoff modulation frequency at 800Hz, depending on the carrier pulse rate. The relative contribution of the temporal effects on ECAP amplitudes is greatest at low stimulus levels and low modulation depths. PMID:19015019

Jeng, Fuh-Cherng; Abbas, Paul J; Hu, Ning; Miller, Charles A; Nourski, Kirill V; Robinson, Barbara K

2009-01-01

135

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

136

Parametric resonances in the amplitude-modulated probe-field absorption spectrum of a two-level atom driven by a resonance amplitude- and phase-modulated pumping field  

International Nuclear Information System (INIS)

An analytical expression is derived for the polarization induced by a weak probe field with periodically modulated amplitude in a two-level medium saturated by a strong amplitude-and phase-modulated resonance field. It is shown that the absorption spectrum of the probe field includes parametric resonances, the maxima corresponding to the condition ?= 2n?-?w and the minima to that of ?= (2n + 1)?- w, where ? is the probe-field detuning front the resonance frequency, ?w is the modulation frequency of the probe-field amplitude, and ? is the transition line width, n = 1, 2, 3, hor-ellipsis. At the specific modulation parameters, a substantial region of negative values (i.e., the region of amplification without the population inversion) exists in the absorption spectrum of the probe field

137

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

138

Early detection of spontaneous blood loss using amplitude modulation of Photoplethysmogram.  

Science.gov (United States)

The present study was designed to investigate can the amplitude modulation (AM) of Photoplethysmogram (PPG) be used as an indicator of blood loss and if so what is the best PPG probe site. PPG from ear, finger and forehead probe sites, standard ECG, and Finapres blood pressure waveforms were continuously recorded from 8 healthy volunteers during baseline, blood withdrawal of 900 ml followed by the blood reinfusion. The instantaneous amplitude modulations present in heart rate (AM(HR)) and breathing rate (AM(BR)) band frequencies of PPG were extracted from high-resolution time-frequency spectrum. HR and pulse pressure showed no significant changes during the protocol. The AM(HR) significantly (P<0.05) decreased at 100 ml through 900 ml blood loss from ear and finger probe sites. The mean percent decrease in AM(HR) at 900 ml blood loss compared to baseline value was 45.2%, 42.0%, and 42.3% for ear, finger and forehead PPG signals, respectively. In addition, significant increases in AM(BR) were found due to blood loss in ear and finger PPG signals. Even without baseline AM(HR) values, 900 ml blood loss detection was shown possible with specificity and sensitivity both 87.5% from ear PPG signals. The present technique has great potential to serve as a valuable tool in the intraoperative and trauma settings to detect hemorrhage. PMID:22255583

Selvaraj, Nandakumar; Scully, Christopher G; Shelley, Kirk H; Silverman, David G; Chon, Ki H

2011-01-01

139

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

DEFF Research Database (Denmark)

Diverging results have been reported regarding the modulation and amplitude of the soleus H-reflex measured during human walking and running. A possible explanation to this could be the use of too high stimulus strength in some studies while not in others. During activities like walking and running it is necessary to use a small M-wave to control the effective stimulus strength during all phases of the movement. This implies that the descending part of the H-reflex recruitment curve is being used, which may lead to an unwanted suppression of the H-reflex due to limitations imbedded within the H-reflex methodology itself. Accordingly, the purpose of the present study was to study the effect on the soleus H-reflex during walking and running using stimulus intensities normally considered too high (up to 45% Mmax). Using M-waves of 25-45% Mmax as opposed to 5-25% Mmax showed a significant suppression of the peak H-reflex during the stance phase of walking, while no changes were observed during running. No differences were observed regarding modulation pattern. So a possible use of too high stimulus intensity cannot explain the differences mentioned. The surprising result in running may be explained by the much higher voluntary muscle activity, which implies the existence of a V-wave influencing the H-reflex amplitude in positive direction.

Simonsen, Erik B; Alkjær, Tine

2013-01-01

140

Amplitude modulated heterodyne reflectometer for density profile and density fluctuation profile measurements at W7-AS  

International Nuclear Information System (INIS)

A broadband heterodyne reflectometer operating in the frequency range 75 endash 110 GHz in extraordinary mode polarization is used at the W7-AS stellarator for both fast density profile determination and density fluctuation studies. The probing signal is amplitude modulated at a frequency 133 MHz using the envelope phase for profile evaluation and the carrier phase to determine the fluctuation information simultaneously. Separate Gaussian beam optics for final signal launch and detection permits a beam waist of about 2 cm at the reflecting layer in the plasma. Amplitude modulated detection is accomplished in the intermediate frequency part by synchronous detection after recovery of the carrier by narrow-band filtering. Voltage controlled solid state oscillators followed by active frequency multiplication allow to scan the full frequency band within less than 1 ms. For typical W7-AS operation the accessible density range is 1x1019 to 6x1019 m-3 for on axis magnetic field of 2.5 T and 4.5x1019 to 10x1019 m-3 for 1.25 T, respectively. The probed radial positions range between 0.2< r/a<1.1 depending on plasma conditions (a?17 cm). copyright 1996 American Institute of Physics

141

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

International Nuclear Information System (INIS)

Amplitude Modulated reflectometry is presented here as a tool for density profile measurements in the JET divertor plasmas. One of the main problems which has been present in most reflectometers during the last years is the need for a coherent tracking of the phase delay: fast density fluctuations and strong modulation on the amplitude of the reflected signal usually bring to fringe jumps in the phase signal, which are a big problem when the phase values are much larger than 2? The conditions in the JET divertor plasmas: plasma geometry, access and long oversized broad- band waveguide paths makes very difficult the phase measurements at the millimeter wave range. AM reflectometry is to some extension an intermediate solution between the classical phase delay reflectometry, so far applied to small distances, and the time domain reflectometry, used for onospheric studies and recently also proposed for fusion plasmas. The main advantage is to allow the use of millimeter wave reflectometry with moderate phase shifts ( ? 2? ). (Author) 2 refs

142

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

Science.gov (United States)

We present a superpixel method for full spatial phase and amplitude control of a light beam using a digital micromirror device (DMD) combined with a spatial filter. We combine square regions of nearby micromirrors into superpixels by low pass filtering in a Fourier plane of the DMD. At each superpixel we are able to independently modulate the phase and the amplitude of light, while retaining a high resolution and the very high speed of a DMD. The method achieves a measured fidelity F = 0.98 for a target field with fully independent phase and amplitude at a resolution of 8 × 8 pixels per diffraction limited spot. For the LG10 orbital angular momentum mode the calculated fidelity is F = 0.99993, using 768 × 768 DMD pixels. The superpixel method reduces the errors when compared to the state of the art Lee holography method for these test fields by 50% and 18%, with a comparable light efficiency of around 5%. Our control software is publicly available. PMID:25089419

Goorden, Sebastianus A; Bertolotti, Jacopo; Mosk, Allard P

2014-07-28

143

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

International Nuclear Information System (INIS)

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

144

Hierarchical effects of task engagement on amplitude modulation encoding in auditory cortex.  

Science.gov (United States)

We recorded from middle lateral belt (ML) and primary (A1) auditory cortical neurons while animals discriminated amplitude-modulated (AM) sounds and also while they sat passively. Engagement in AM discrimination improved ML and A1 neurons' ability to discriminate AM with both firing rate and phase-locking; however, task engagement affected neural AM discrimination differently in the two fields. The results suggest that these two areas utilize different AM coding schemes: a "single mode" in A1 that relies on increased activity for AM relative to unmodulated sounds and a "dual-polar mode" in ML that uses both increases and decreases in neural activity to encode modulation. In the dual-polar ML code, nonsynchronized responses might play a special role. The results are consistent with findings in the primary and secondary somatosensory cortices during discrimination of vibrotactile modulation frequency, implicating a common scheme in the hierarchical processing of temporal information among different modalities. The time course of activity differences between behaving and passive conditions was also distinct in A1 and ML and may have implications for auditory attention. At modulation depths ? 16% (approximately behavioral threshold), A1 neurons' improvement in distinguishing AM from unmodulated noise is relatively constant or improves slightly with increasing modulation depth. In ML, improvement during engagement is most pronounced near threshold and disappears at highly suprathreshold depths. This ML effect is evident later in the stimulus, and mainly in nonsynchronized responses. This suggests that attention-related increases in activity are stronger or longer-lasting for more difficult stimuli in ML. PMID:25298387

Niwa, Mamiko; O'Connor, Kevin N; Engall, Elizabeth; Johnson, Jeffrey S; Sutter, M L

2015-01-01

145

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Frederico P. Costa

2013-11-01

146

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

Science.gov (United States)

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

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

2014-07-01

147

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

148

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

OpenAIRE

Reduced hen lysozyme has a residual structure involving long-range interaction. It has been demonstrated that a single mutation (A9G, W62G, W111G, or W123G) in the residual structure differently modulates the long-range interactions of reduced lysozyme. To examine whether such variations in the residual structure affect amyloid formation, reduced and alkylated mutant lysozymes were incubated under the amyloid-fibrillation condition. From the analyses of CD spectra and thioflavine T fluorescen...

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

2006-01-01

149

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

150

Magnetic excitations in the longitudinally amplitude modulated magnetic structure of PrNi2Si2  

International Nuclear Information System (INIS)

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

151

Modulated Amplitude Waves and the Transition from Phase to Defect Chaos  

CERN Document Server

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

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

2000-01-01

152

First Results with a Fast Phase and Amplitude Modulator for High Power RF Application  

CERN Document Server

In a high energy and high power superconducting proton linac, it is more economical to drive several cavities with a single high power transmitter rather than to use one transmitter per cavity. However, this option has the disadvantage of not permitting individual control for each cavity, which potentially leads to instabilities. Provided that it can be built at a reasonable cost, a fast phase and amplitude modulator inserted into each cavity feeder line can provide the necessary control capability. A prototype of such a device has been built, based on two fast and compact high power RF phase-shifters, magnetically biased by external coils. The design is described, together with the results obtained at high and low power levels.

Frischholz, Hans; Valuch, D; Weil, C

2004-01-01

153

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

154

Slow light of an amplitude modulated Gaussian pulse in electromagnetically induced transparency medium  

CERN Document Server

The slow light effects of an amplitude modulated Gaussian (AMG) pulse in a cesium atomic vapor cell are presented. In a single-$\\Lambda$ type electromagnetically induced transparency (EIT) medium, more severe distortion is observed for the AMG pulse than a Gaussian one. Using Fourier spectrum analysis, we find that it is the linear absorption of the medium that mainly causes the loss and distortion of the slowed pulse. Further, it is found that the dispersion determines the group velocities and causes an additional distortion of the AMG pulse due to its spectral distribution. Based on the transmission (absorption) spectrum, we propose a post-processing method to recover the shape and intensity of the slowed pulse. In addition, this method reveals a novel way to obtain the simultaneously slow and fast light of different spectral components of a single pulse.

Tang, Wenzhuo; Liu, Yu; Guo, Hong

2009-01-01

155

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

156

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

Science.gov (United States)

Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA) for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose, we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators (SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 ?/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.

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

2014-08-01

157

Influence of 100Hz amplitude modulation on the human medial olivocochlear reflex.  

Science.gov (United States)

It is well known that medial olivocochlear system (MOC) activity causes inhibition of cochlear amplification that can be measured using otoacoustic emissions (OAEs). The temporal characteristics of this MOC inhibitory effect are still not well understood. Two experiments were performed to further explore a previously reported enhancement in MOC inhibition of OAEs by a broadband noise (BBN) elicitor modulated at 100Hz (AM-BBN). In experiment I, MOC inhibition was measured for toneburst (1 and 2kHz presented at 41.67Hz) and stimulus-frequency (0.96-1.92kHz) OAEs for two elicitor conditions, BBN and AM-BBN (100% modulation depth [MD]), in 27 young normal hearing adults. In experiment II, tonebursts were presented at 50Hz instead of 41.67Hz to test if the previously reported enhancement of the MOC response to 100Hz AM-BBN is specific to a 50Hz toneburst presentation rate. All elicitors caused significant reduction of both TB- and SF-OAE amplitude. AM-BBN evoked the same OAE inhibition compared to BBN in both experiments. This pattern was consistent across OAE types, and toneburst presentation rates. Results suggest that the MOC is not especially sensitive to 100Hz AM-BBN; instead, AM dips in noise energy likely reduce its effectiveness in evoking MOC activity due to temporal energy integration. PMID:25102324

Boothalingam, Sriram; Purcell, David; Scollie, Susan

2014-09-19

158

Changes in auditory nerve responses across the duration of sinusoidally amplitude-modulated electric pulse-train stimuli.  

Science.gov (United States)

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 intracochlear electrode had fixed modulation frequency (100 Hz) and depth (10%). ANF responses were assessed by spike-rate measures, while representation of modulation was evaluated by vector strength (VS) and the fundamental component of the fast Fourier transform (F(0) amplitude). These measures were assessed across the 400 ms duration of pulse-train stimuli, a duration relevant to speech stimuli. Different stimulus levels were explored and responses were categorized into four spike-rate groups to assess level effects across ANFs. The temporal pattern of rate adaptation to modulated trains was similar to that of unmodulated trains, but with less rate adaptation. VS to the modulator increased over time and tended to saturate at lower spike rates, while F(0) amplitude typically decreased over time for low driven rates and increased for higher driven rates. VS at moderate and high spike rates and degree of F(0) amplitude temporal changes at low and moderate spike rates were positively correlated with the degree of rate adaptation. Thus, high-rate carriers will modify the ANF representation of the modulator over time. As the VS and F(0) measures were sensitive to adaptation-related changes over different spike-rate ranges, there is value in assessing both measures. PMID:20632064

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

2010-12-01

159

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

160

Digital quadrature amplitude modulation with optimized non-rectangular constellations for 100 Gb/s transmission by a directly-modulated laser.  

Science.gov (United States)

We study the performance of novel quadrature amplitude modulation (QAM) constellations for 100 Gb/s transmission by a directly-modulated laser. Due to the strong nonlinearity of a directly-modulated laser, rectangular constellations suffer a large penalty from their regular spacing between symbols. We present a method for synthesizing irregular constellations which position symbols more efficiently. We will demonstrate the improved performance of these novel constellations over the conventional rectangular constellation as well as the superior performance achievable with digital QAM compared to optimally bit-loaded discrete-multitone modulation. PMID:24921784

Ling, William A; Lyubomirsky, Ilya; Solgaard, Olav

2014-05-01

161

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

International Nuclear Information System (INIS)

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

162

A new minimum fluorescence parameter, as generated using pulse frequency modulation, compared with pulse amplitude modulation: Falpha versus Fo.  

Science.gov (United States)

The minimum fluorescence parameter (Falpha), generated using the new pulse frequency modulation (PFM) technology, was compared with the minimum fluorescence parameter (Fo), generated by pulse amplitude modulation (PAM), in response to a reversible low-oxygen stress in 'Honeycrisp'trade mark (HC) apples (Malus domestica) and an irreversible osmotic stress induced by water loss in two grape (Vitis spp.) cultivars ('L'Acadie' (LAc) and 'Thompson Seedless' (TS)). The minimum fluorescence values produced by both fluorometer types in response to a reversible low-oxygen stress in apples were indistinguishable: both Fo and Falpha increased when O2 levels were lowered below the anaerobic compensation point (ACP); when gas levels returned to normoxia both parameters dipped below, then returned to, the original fluorescence baseline. The two parameters also responded similarly to the irreversible osmotic stress in grapes: in both cultivars, Falpha and Fo first decreased before reaching an inflection point at approximately 20% mass loss and then increased towards a second inflection point. However, the two parameters were not analogous under the irreversible osmotic stress; most notably, the relative Falpha values appeared to be lower than Fo during the later stages of dehydration. This was likely due to the influence of the Fm parameter and an overestimation of Falpha when measuring the fluorescence from healthy and responsive chloroplasts as found in grapes experiencing minimal water loss, but not in grapes undergoing moderate to severe dehydration. An examination of the data during a typical PFM scan reveals this fluorometer system may yield new fluorescence information with interesting biological applications. PMID:18668341

Wright, A Harrison; DeLong, John M; Franklin, Jeffrey L; Lada, Rajasekaran R; Prange, Robert K

2008-09-01

163

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

Science.gov (United States)

The responses of single neurons of the cochlear nucleus of a grass frog to long tonal signals amplitude-modulated by repeat intervals of low-frequency noise have been studied. The carrier frequency always corresponded to the characteristic frequency of the studied cell (a range of 0.2 kHz-2 kHz); the modulated signal was noise in the ranges 0-15 Hz, 0-50 Hz, or 0-150 Hz. We obtained the correlation functions of the cyclic histogram reflecting the change in probability of a neuron pulse discharge (spike) during the modulation period with the shape of the signal envelope in the same period. The form of the obtained correlation functions usually does not change qualitatively with a change in carrier level or modulation depth; however, this could essentially depend of the frequency component of the modulating function. In the majority of cases, comparison of the cyclic histogram of the reaction with only the current amplitude value does not adequately reveal the signal's time features that determine the reaction of a neuron. The response is also determined by the other sound features, primarily by the rate of the change in amplitude. The studied neurons differed among themselves, both in preference toward a certain range of modulated frequencies and in the features of the envelope that caused the cell's response.

Bibikov, N. G.

2014-09-01

164

Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel.  

Science.gov (United States)

The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins ((13)C and (1)H) at 12mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128kHz ((13)C) and 510kHz ((1)H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as hardware complexity and bulk, weighed against the caveat that elaborate pulses are required. More work will be necessary to test this method on the targeted application of parahydrogen induced hyperpolarization as well as to quantify efficiency, but upon further development we anticipate that this method may offer a viable 'software' approach to heteronuclear manipulations of spins at low magnetic fields. PMID:24954513

Moore, Jay; Colón, Raul D; Tadanki, Sasidhar; Waddell, Kevin W

2014-08-01

165

Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel  

Science.gov (United States)

The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins (13C and 1H) at 12 mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128 kHz (13C) and 510 kHz (1H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as hardware complexity and bulk, weighed against the caveat that elaborate pulses are required. More work will be necessary to test this method on the targeted application of parahydrogen induced hyperpolarization as well as to quantify efficiency, but upon further development we anticipate that this method may offer a viable ‘software’ approach to heteronuclear manipulations of spins at low magnetic fields.

Moore, Jay; Colón, Raul D.; Tadanki, Sasidhar; Waddell, Kevin W.

2014-08-01

166

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)

167

Coding of time-varying electric field amplitude modulations in a wave-type electric fish.  

Science.gov (United States)

1. The coding of time-varying electric fields in the weakly electric fish, Eigenmannia, was investigated in a quantitative manner. The activity of single P-type electroreceptor afferents was recorded while the amplitude of an externally applied sinusoidal electric field was stochastically modulated. The amplitude modulation waveform (i.e., the stimulus) was reconstructed from the spike trains by mean square estimation. 2. From the stimulus and the reconstructions we calculated the following: 1) the signal-to-noise ratio and thus an effective temporal bandwidth of the units; 2) the coding fraction, i.e., a measure of the fraction of the time-varying stimulus encoded in single spike trains; and 3) the mutual information provided by the reconstructions about the stimulus. 3. Signal-to-noise ratios as high as 7:1 were observed and the bandwidth ranged from 0 up to 200 Hz, consistent with the limit imposed by the sampling theorem. Reducing the cutoff frequency of the stimulus increased the signal-to-noise ratio at low frequencies, indicating a nonlinearity in the receptors' response. 4. The coding fraction and the rate of mutual information transmission increased in parallel with the standard deviation (i.e., the contrast) of the stimulus as well as the mean firing rate of the units. Significant encoding occurred 20-40 Hz above the spontaneous discharge of a unit. 5. When the temporal cutoff frequency of the stimulus was increased between 80 and 400 Hz, 1) the coding fraction decreased, 2) the rate of mutual information transmission remained constant over the same frequency range, and 3) the reconstructed filter changed. This is in agreement with predictions obtained in a simplified neuronal model. 6. Our results suggest that 1) the information transmitted by single spike trains of primary electrosensory afferents to higherorder neurons in the fish brain depends on the contrast and the cutoff frequency of the stimulus as well as on the mean firing rate of the units; and 2) under optimal conditions, more than half of the information about a Gaussian stimulus that can in principle be encoded is carried in single spike trains of P-type afferents at rates up to 200 bits per second. PMID:8793741

Wessel, R; Koch, C; Gabbiani, F

1996-06-01

168

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

OpenAIRE

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

169

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

DEFF Research Database (Denmark)

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

Rodes Lopez, Roberto; Wieckowski, Marcin

2011-01-01

170

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

Science.gov (United States)

We experimentally demonstrate successful performance of VCSEL-based WDM link supporting advanced 16-level carrierless amplitude/phase modulation up to 1.25 Gbps, over 26 km SSMF with spectral efficiency of 4 bit/s/Hz for application in high capacity PONs. PMID:22274239

Rodes, Roberto; Wieckowski, Marcin; Pham, Thang Tien; Jensen, Jesper Bevensee; Turkiewicz, Jarek; Siuzdak, Jerzy; Monroy, Idelfonso Tafur

2011-12-19

171

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

DEFF Research Database (Denmark)

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

Rodes Lopez, Roberto; Wieckowski, Marcin

2011-01-01

172

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

Science.gov (United States)

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

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

2013-05-15

173

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

International Nuclear Information System (INIS)

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. (paper)

174

Transit-time broadening in pulsed Doppler ultrasound: a generalized amplitude modulation model.  

Science.gov (United States)

In Doppler ultrasound, transit-time broadening arises from the finite scatterer transit time through the sample volume. As a unifying description of this broadening mechanism, a generalized amplitude modulation signal model was developed to collectively account for the transit-time effects of the ultrasound beam geometry and the range gate characteristics. Simulations based on a pulsed linear-array system also were performed to study the broadening extent for different scatterer flow lines. With our signal model and simulation results, some generalized insights were obtained on the characteristics of transit-time broadening. First, as consistent with previous findings, we found that, for scatterers passing though the center of the sample volume, the broadening extent mainly depends on beam-forming characteristics at higher beam-flow angles, but it is more dependent on range gate parameters at smaller angles. Second, for the central flow line, a transition angle exists in which a significant change occurs in the governing parameters of transit-time broadening. Third, for the general case in which scatterers undertake an off-central path through the sample volume, the broadening extent depends on both the beam geometry and the range gate. Bandwidth skewing and further spectral broadening also can be seen for these off-central flow lines. PMID:16555761

Yu, Alfred C H; Steinman, Aaron H; Cobbold, Richard S C

2006-03-01

175

Blind adaptive equalizers for quadrature amplitude modulated communication systems based on convex cost functions  

Science.gov (United States)

Blind adaptive channel equalizers are important devices to remove channel distortion in high data-rate, bandlimited digital communication systems when the transmission of a training sequence is impractical or very costly. Traditional blind equalization algorithms adapt the equalizer parameters to minimize some specially designed non-MSE cost functions. These algorithms can experience local convergence problems and can thereby result in insufficient or no removal of channel distortion. We present a new quadrature amplitude modulated blind equalization scheme that is globally convergent in the equalizer parameter space to a compact set containing the desired ideal equalizer parameter setting. Our new algorithm is based on a convex cost function and a linear constraint on the equalizer parameters. For a generic class of channels, this new algorithm results in the equalizer parameter convergence to a unique global minimum achieving intersymbol interference suppression and carrier phase error removal. Different implementation approaches are assessed and simulation results are shown to confirm the theoretical global convergence of the new algorithm.

Kennedy, Rodney A.; Ding, Zhi

1992-06-01

176

Frequency-selective manipulation of spin waves: micromagnetic texture as amplitude valve and mode modulator  

Science.gov (United States)

Spin–wave devices are regarded as one of the most promising candidates for future computation and data processing. How to manipulate spin–wave propagation is a key issue in realizing the functionality of these of devices. The existing manipulation methods have serious drawbacks for constructing practical spin–wave devices. Here, we propose an approach to harness the amplitude and mode excitation of traveling spin waves by introducing unique micromagnetic textures in a permalloy waveguide directly exchange-coupled to a pair of cobalt nanomagnets. We demonstrate that the imprinted micromagnetic textures, i.e., the 360° domain wall and magnetic buckle, which play different roles in spin–wave manipulation, can be interchanged with each other repeatedly by using a sequence of homogeneous magnetic fields. Moreover, the suggested architecture could easily be tailored to implement fundamental logic-NOT operation. In light of the internal-field profile of the micromagnetic textures, speculation is offered concerning the physical origin underlying the observed spin–wave modulation phenomena.

Xing, Xiangjun; Jin, Qingli; Li, Shuwei

2015-02-01

177

Enhanced 16 Spiral quadrature amplitude modulation scheme for coherent optical orthogonal frequency division multiplexing systems  

Science.gov (United States)

We propose an enhanced 16 Spiral quadrature amplitude modulation (QAM) (16 E-Spiral QAM) scheme to overcome the laser phase noise in a coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Considering both additive white Gaussian noise and large phase noise, 16 E-Spiral QAM schemes have a better transmission performance compared to conventional 16 QAM CO-OFDM systems. The simulated results show that the required optical signal-to-noise ratio (OSNR) of the proposed 16 QAM is, respectively, 0.8 and 2.3 dB less than 16 Spiral and conventional 16 QAM at a bit error rate (BER) of 10-3 in a back-to-back case. After 800-km transmission over a single-mode fiber, the tolerance for the laser linewidth of the 16 E-Spiral QAM can improve about 30 kHz with an OSNR of 18 dB compared to that of a conventional 16 QAM.

He, Jing; Li, Chong; Chen, Lin; Chen, Ming

2014-09-01

178

Digital services using quadrature amplitude modulation (QAM) over CATV analog DWDM system  

Science.gov (United States)

Dense Wavelength Division Multiplexing (DWDM) has recently gained great popularity as it provides a cost effective way to increase the transmission capacity of the existing fiber cable plant. For a long time, Dense WDM was exclusively used for baseband digital applications, predominantly in terrestrial long haul networks and in some cases in metropolitan and enterprise networks. Recently, the performance of DWDM components and frequency-stabilized lasers has substantially improved while the costs have down significantly. This makes a variety of new optical network architectures economically viable. The first commercial 8- wavelength DWDM system designed for Hybrid Fiber Coax networks was reported in 1998. This type of DWDM system utilizes Sub-Carrier Multiplexing (SCM) of Quadrature Amplitude Modulated (QAM) signals to transport IP data digital video broadcast and Video on Demand on ITU grid lightwave carriers. The ability of DWDM to provide scalable transmission capacity in the optical layer with SCM granularity is now considered by many to be the most promising technology for future transport and distribution of broadband multimedia services.

Yeh, JengRong; Selker, Mark D.; Trail, J.; Piehler, David; Levi, Israel

2000-04-01

179

Efficient Amplitude-Modulated Pulses for Triple- to Single-Quantum Coherence Conversion in MQMAS NMR  

Science.gov (United States)

The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed “too challenging”. PMID:25047226

2014-01-01

180

Method of Phase and Amplitude Modulation/Demodulation Using Datapages with Embedded Phase-Shift for Holographic Data Storage  

Science.gov (United States)

A technique for the phase and amplitude detection of object beams with multivalued phase and amplitude modulation is proposed for holographic storage systems. Generally, the spatial distribution of the complex amplitude of the object beam can be precisely detected by phase-shifting interferometric measurements in which the phase of the reference wave for interferometry is temporally or spatially changed in the datapage retrieval process. On the other hand, our technique allows fast, accurate, and feasible phase and amplitude demodulations by preliminary embedding phase shift into the phase signal of the datapage during recording. This technique will significantly improve the data transfer rate and vibration tolerance of the holographic storage system because the complex amplitudes of the object beam carrying datapages can be detected by single-shot image capturing. The optical system for datapage replay will also be simplified because there is no need to use any phase-shifting device during data retrieval. The single-shot detection of the phase-modulated datapage is experimentally demonstrated.

Bunsen, Masatoshi; Umetsu, Shuhei; Takabayashi, Masanori; Okamoto, Atsushi

2013-09-01

181

Experimental measurements and influence of overload-induced residual stress field on constant amplitude fatigue crack growth in aluminum alloy  

Science.gov (United States)

The aim of this research is to investigate current methods in Linear Elastic Fracture Mechanics for their suitability to predict crack growth in Aluminum alloy 7050 - T7451, when a compressive residual stress field is introduced by an overload. A comparative study has been made on the effect of various levels of tensile overload on the crack growth rate in Aluminum alloy. Experiments were performed on center-cracked tension specimens at various values of range of stress- intensity-factor ((Delta) K). Crack growth measurements are performed using crack propagation gauges and a travelling microscope. The average crack growth rate is used to determine an effective (Delta) K value for each interval using the fatigue crack propagation curve. After the application of overloads, the propagation gauges revealed a period of significant retardation before the crack growth rates returned to their baseline levels. The results from the numerical predictions are compared with the experimental results. The prediction model produces conservative results for both constant amplitude crack growth and overload induced retarded growth.

Wahab, M. A.; Rohrsheim, G. R.; Brown, I. H.

1997-03-01

182

Conformational modulation of Ant-Pro oligomers using chirality alteration of proline residues.  

Science.gov (United States)

Structural modulation of Ant-Pro (anthranilic acid-proline) oligomers has been carried out by chirality alteration of the proline residues. The results suggest that the chirality altered oligomers show well-defined helical conformation featuring nine-membered hydrogen bonding interactions - without compromising conformational rigidity. PMID:23001178

Kale, Sangram S; Kotmale, Amol S; Dutta, Achintya Kumar; Pal, Sourav; Rajamohanan, P R; Sanjayan, Gangadhar J

2012-11-14

183

Conserved residues that modulate protein trans-splicing of Npu DnaE split intein.  

Science.gov (United States)

The first crystal trans-structure of a naturally occurring split intein has been determined for the Npu (Nostoc punctiforme PCC73102) DnaE split intein. Guided by this structure, the residues NArg50 and CSer35, well conserved in DnaE split inteins, are identified to be critical in the trans-splicing of Npu DnaE split intein. An in vitro splicing assay demonstrates that NArg50 and CSer35 play synergistic roles in modulating its intein activity. The C-terminal CAsn36 exhibits two orientations of its side chain and interacts with both NArg50 and CSer35 through hydrogen bonding. These interactions likely facilitate the cyclization of asparagine in the course of protein splicing. The mutation of either residue reduces intein activity, and correlates with the low activity of the Ssp (Cyanobacterium synechocystis sp. strain PCC6803) DnaE split intein. On the other hand, NArg50 also forms a hydrogen bond with the highly conserved F-block CAsp17, thus influencing the N-S acyl shift during N-terminal cleavage. Sequence alignments show that residues NArg50 and CSer35 are rather conserved in those split inteins that lack a penultimate histidine residue. The conserved non-catalytic residues of split inteins modulate the efficiency of protein trans-splicing by hydrogen-bond interactions with the catalytic residues at the splice junction. PMID:24758175

Wu, Qin; Gao, Zengqiang; Wei, Yong; Ma, Guolin; Zheng, Yuchuan; Dong, Yuhui; Liu, Yangzhong

2014-07-15

184

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)

185

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

International Nuclear Information System (INIS)

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

186

Stochastic Resonance in a Single-Mode Laser Driven by Quadratic Colored Pump Noise: Effects of Biased Amplitude Modulation Signal  

International Nuclear Information System (INIS)

A single-mode laser noise model driven by quadratic colored pump noise and biased amplitude modulation signal is proposed. The analytic expression of signal-to-noise ratio is calculated by using a new linearized procedure. It is found that there are three different typies of stochastic resonance in the model: the conventional form of stochastic resonance, the stochastic resonance in the broad sense, and the bona fide SR.

187

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

CERN Document Server

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

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

2001-01-01

188

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

OpenAIRE

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 rej...

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

2010-01-01

189

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

Energy Technology Data Exchange (ETDEWEB)

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 /sup 45/Ca/sup 2 +/ efflux from the avian brain tissue. Statistical analysis of these data demonstrates that such exposure has no significant effect on /sup 45/Ca/sup 2 +/ efflux.

Albert, E.N.; Slaby, F.; Roche, J.; Loftus, J.

1987-01-01

190

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

191

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

192

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

193

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

194

Eliminating bistability and reducing sample damage through frequency and amplitude modulation in tapping-mode atomic force microscopy  

Science.gov (United States)

Since its invention, amplitude-modulation tapping-mode atomic force microscopy (AM-AFM) has rapidly developed into a common high-resolution surface characterization tool. However, despite the technical advances, imaging bistability caused by the coexistence of the so-called attractive and repulsive imaging regimes, and potential sample damage in the repulsive regime (often critical in biological and other soft-sample applications) still remain as fundamental barriers which prevent users from consistently obtaining high-quality images. This report proposes a new intermittent-contact AFM imaging concept, frequency- and amplitude-modulation atomic force microscopy (FAM-AFM), which offers the potential to overcome both issues. This imaging method combines existing knowledge from non-contact frequency-modulation atomic force microscopy (FM-AFM) and AM-AFM in a new control scheme involving the use of variable excitation force amplitude and frequency to control the cantilever effective frequency and limit the magnitude of the tip-sample repulsive forces. As in FM-AFM, within the new scheme the cantilever is continuously excited at its (variable) effective frequency so it is not prone to bistability. Control of the repulsive forces is achieved through the adjustment of the excitation force amplitude, so that the effective frequency always remains below the free resonant frequency. Promising results from numerical simulations are presented for single-walled carbon nanotube (SWNT) and silicon tips interacting with a Si(100)-OH surface, and for SWNT tips interacting with the same surface while intermittently forming and breaking covalent bonds, and while experiencing attractive electrostatic interactions.

Solares, Santiago D.

2007-03-01

195

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

DEFF Research Database (Denmark)

Input power dynamic range enhancement and amplitude regeneration of highly distorted signals are demonstrated experimentally for 40 Gbit/s RZ-DPSK in a single-pump fibre parametric amplifier with 22 dB smallsignal gain.

Peucheret, Christophe; Lorenzen, Michael Rodas

2008-01-01

196

Performances of Hybrid Amplitude Shape Modulation for UWB Communications Systems over AWGN Channel in a Single and Multi-User Environment  

Directory of Open Access Journals (Sweden)

Full Text Available This paper analyzes the performance of the hybrid Amplitude Shape Modulation (h-ASM scheme for the time-hopping ultra-wideband (TH-UWB communication systems in the single and multi-user environment. h-ASM is the combination of Pulse Amplitude Modulation (PAM and Pulse Shape Modulation (PSM based on modified Hermite pulses (MHP. This scheme is suitable for high rate data transmission applications because b = log2(MN bits can be mapped with one waveform. The channel capacity and error probability over AWGN channel are derived and compared with other modulation schemes.

M. Herceg

2009-09-01

197

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

Directory of Open Access Journals (Sweden)

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

Hassan Farhan Rashag

2013-04-01

198

Investigation into factors affecting precision in ion trap mass spectrometry using different scan directions and axial modulation potential amplitudes.  

Science.gov (United States)

Electrospray ionization mass spectra obtained from different scan directions are observed to be dependent on the axial modulation potential amplitudes used for resonant ejection and on the positive deviation caused by higher even-multipole fields present in most commercial ion traps. The axial modulation voltage influences the dissociation of ions during resonant ejection and the observed mass shifts. The higher even-multipole fields in commercial ion traps are known to influence resonant ejection from the ion trap and can cause a loss in mass resolution for peaks in reverse scan mass spectra compared with that obtained by the forward scan. However, along with the dissociation of ions during resonant ejection causing a loss in resolution, the possibility of resolving an isotopic distribution is also shown to be influenced by the mass shifts caused by the space charge. These mass shifts differ depending on the scan direction employed. A significant loss in resolution can also result from resonant ejection using non-optimal axial modulation voltages. We also present results showing the ejection of ions at betaz = 1/2 using the reverse scan mode without the axial modulation voltage. Ion ejection at betaz = 1/2 is uncommon in commercial (stretched ion traps) with the conventional analytical scan without the use of a frequency of the axial modulation voltage corresponding to this non-linear resonance. PMID:15472990

Dobson, G; Murrell, J; Despeyroux, D; Wind, F; Tabet, J-C

2004-11-01

199

A high-resolution two-pulse coherent anti-Stokes Raman scattering spectrum using a spectral amplitude modulation  

International Nuclear Information System (INIS)

Femtosecond coherent anti-Stokes Raman scattering (CARS) spectra suffer from low spectral resolution because of the broadband laser spectrum. In this paper, we propose a feasible scheme to achieve a high-resolution two-pulse CARS spectrum by shaping both the pump and probe pulses using rectangular amplitude modulation. We show that a narrowband hole in the CARS spectrum can be created by the amplitude-shaped laser pulse, the position of which is correlated with the Raman resonant frequency of the molecule. Thus, by observing holes in the CARS spectrum, we are able to obtain a high-resolution CARS spectrum and the energy-level diagram of the molecule. (paper)

200

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

201

Amplitude Variation Effects Of Phase Modulators In A Serrodyne Fiber-Optic Gyroscope  

Science.gov (United States)

We have investigated the amplitude variation effects in a serrodyne fiber-optic gyroscope (FOG). As the results of numerical calculation, it became clear that there are bias, scale factor error and discontinuity in regard to the linear relationship between serrodyne frequency and sagnac phase shift. And we confirmed those errors experimentally.

Kaku, Ryoji

1990-02-01

202

Stochastic resonance in a single-mode laser driven by quadratic pump noise and amplitude-modulated signal  

International Nuclear Information System (INIS)

This paper investigates the phenomenon of stochastic resonance in a single-mode laser driven by quadratic pump noise and amplitude-modulated signal. A new linear approximation approach is advanced to calculate the signal-to-noise ratio. In the linear approximation only the drift term is linearized, the multiplicative noise term is unchangeable. It is found that there appears not only the standard form of stochastic resonance but also the broad sense of stochastic resonance, especially stochastic multiresonance appears in the curve of signal-to-noise ratio as a function of coupling strength ? between the real and imaginary parts of the pump noise. (general)

203

Amplitude modulation of oscillatory activity in the subthalamic nucleus during movement.  

OpenAIRE

Depth recordings in patients with Parkinson's disease (PD) have demonstrated exaggerated local field potential (LFP) activity at frequencies between 10 and 30 Hz in the subthalamic nucleus (STN). This activity is modulated prior to single phasic movements, possibly as part of the feedforward organization of incipient voluntary movement, and after single phasic movements, as a consequence of afferent feedback processes. Here we test the hypothesis that this activity is also modulated during re...

Androulidakis, Ag; Bru?cke, C.; Kempf, F.; Kupsch, A.; Aziz, T.; Ashkan, K.; Ku?hn, Aa; Brown, P.

2008-01-01

204

Contribution of very low amplitude-modulation rates to intelligibility in a competing-speech task (L).  

Science.gov (United States)

It is generally agreed that the slow fluctuations in the envelope of speech in different spectral channels carry critical information for intelligibility. Previous studies in which amplitude modulation (AM) was selectively removed from the speech signal showed that modulation rates between 4 and 16 Hz are most important, and that rates falling outside this range contribute little or not at all to speech intelligibility. The present study investigated the role of very low (vocoder. The depth of AM with rates below 4, 1.3, or 0.4 Hz was reduced using a multi-channel envelope compressor with a high compression ratio. Data obtained using nine normal-hearing listeners demonstrate that low-rate AM, in the range 0.4-4 Hz, contributes to the intelligibility of relatively long speech utterances, at least for adverse listening conditions in which background noise is present and listeners are forced to rely on envelope cues in a few spectral channels. PMID:19275283

Füllgrabe, Christian; Stone, Michael A; Moore, Brian C J

2009-03-01

205

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

206

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

207

Non-linear response to amplitude-modulated waves in the apical turn of the guinea pig cochlea.  

Science.gov (United States)

Mechanical vibrations of the Hensen's cells were measured in the apical turn of the cochlea in living guinea pigs, in response to amplitude-modulated (AM) sound. The FFT of the input wave consisted of spectral components at the carrier frequency C and two sidebands (C+/-M) separated from the carrier by the modulation frequency M. The FFT of the velocity response consisted of components at: (i) the modulation frequency M, and harmonics n M; (ii) Carrier frequency C and sidebands (C+/-n M); (iii) harmonics of the carrier frequency and their side bands (2C+/-n M); (3C+/-n M); (4C+/-n M); em leader n=1,2,3, em leader,10. The carrier and the first pair of side bands were broadly tuned and nearly linear. Other components were sharply tuned and highly non-linear, suggesting a different origin. Evidence is presented that these components are generated in the non-linear stereocilia dynamics. An important function of this non-linearity is to demodulate the AM wave to extract information contained in the modulation. PMID:12433402

Khanna, S M

2002-12-01

208

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

DEFF Research Database (Denmark)

The paper proposes an approach to constructing feasible examples of dynamical systems with hyperbolic chaotic attractors based on the successive transfer of excitation between two pairs of self-oscillators that are alternately active. An angular variable that measures the relations of the current amplitudes for the two oscillators of each pair undergoes a transformation in accordance with the expanding circle map during each cycle of the process. We start with equations describing the dynamics in terms of complex or real amplitudes and then examine two models based on van der Pol oscillators. One model corresponds to the situation of equality of natural frequencies of the partial oscillators, and another to a nonresonant ratio of the oscillation frequencies relating to each of the two pairs. Dynamics of all models are illustrated with diagrams indicating the transformation of the angular variables, portraits of attractors, Lyapunov exponents, etc. The uniformly hyperbolic nature of the attractor in the stroboscopic Poincare map is confirmed for a real-amplitude version of the equations by computations of statistical distribution of angles between stable and unstable manifolds at a representative set of points on the attractor. In other versions of the equations the attractors relate presumably to the partially hyperbolic class.

Isaeva, Olga B.; Kuznetsov, Sergey P.

2011-01-01

209

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

Science.gov (United States)

The paper proposes an approach to constructing feasible examples of dynamical systems with hyperbolic chaotic attractors based on the successive transfer of excitation between two pairs of self-oscillators that are alternately active. An angular variable that measures the relations of the current amplitudes for the two oscillators of each pair undergoes a transformation in accordance with the expanding circle map during each cycle of the process. We start with equations describing the dynamics in terms of complex or real amplitudes and then examine two models based on van der Pol oscillators. One model corresponds to the situation of equality of natural frequencies of the partial oscillators, and another to a nonresonant ratio of the oscillation frequencies relating to each of the two pairs. Dynamics of all models are illustrated with diagrams indicating the transformation of the angular variables, portraits of attractors, Lyapunov exponents, etc. The uniformly hyperbolic nature of the attractor in the stroboscopic Poincaré map is confirmed for a real-amplitude version of the equations by computations of statistical distribution of angles between stable and unstable manifolds at a representative set of points on the attractor. In other versions of the equations the attractors relate presumably to the partially hyperbolic class. PMID:21867294

Isaeva, Olga B; Kuznetsov, Sergey P; Mosekilde, Erik

2011-07-01

210

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

OpenAIRE

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 st...

Mohammud Ershadul Haque; Mohammud Fauzi Mohammud Zain; Maslina Jamil; Mohammud Abdul Hannan; Abdulla Al Suman

2013-01-01

211

Low-cost optical amplitude modulator based on a tapered single-mode optical fiber.  

Science.gov (United States)

A new, to our knowledge, modulator based on a tapered single-mode optical fiber is introduced. The electro-optic device consists of a tapered optical fiber placed on a resonator made of a piezoelectric material. An electrical signal applied to the piezoelectric material makes the taper bend, and that displacement produces a modulation in the intensity of the optical signal traveling through the fiber. This device is very easy to build and is low in cost. Because of its nature, this new device might be very useful in optical fiber sensors. Its performance is analyzed, and the results are discussed. PMID:18356994

Matías, I R; López-Amo, M; Montero, F; Fernández-Valdivielso, C; Arregui, F J; Bariáin, C

2001-01-10

212

Scanning tunneling microscopy in TTF-TCNQ: Phase and amplitude modulated charge density waves  

DEFF Research Database (Denmark)

Charge density waves (CDWs) have been studied at the surface of a cleaved tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) single crystal using a low temperature scanning tunneling microscope (STM) under ultrahigh-vacuum conditions, between 300 and 33 K with molecular resolution. All CDW phase transitions of TTF-TCNQ have been identified. The measurement of the modulation wave vector along the a direction provides evidence of the existence of domains comprising single plane wave modulated structures in the temperature regime where the transverse wave vector of the CDW is temperature dependent, as hinted by the theory more than 20 years ago.

Wang, Z.Z.; Gorard, J.C.

2003-01-01

213

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

214

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

Science.gov (United States)

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

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

2009-05-20

215

Air segmented amplitude modulated multiplexed flow analysis with software-based phase recognition: determination of phosphate ion.  

Science.gov (United States)

Amplitude modulated multiplexed flow analysis (AMMFA) has been improved by introducing air segmentation and software-based phase recognition. Sample solutions, the flow rates of which are respectively varied at different frequencies, are merged. Air is introduced to the merged liquid stream in order to limit the dispersion of analytes within each liquid segment separated by air bubbles. The stream is led to a detector with no physical deaeration. Air signals are distinguished from liquid signals through the analysis of detector output signals, and are suppressed down to the level of liquid signals. Resulting signals are smoothed based on moving average computation. Thus processed signals are analyzed by fast Fourier transform. The analytes in the samples are respectively determined from the amplitudes of the corresponding wave components obtained. The developed system has been applied to the simultaneous determinations of phosphate ions in water samples by a Malachite Green method. The linearity of the analytical curve (0.0-31.0 ?mol dm(-3)) is good (r(2)>0.999) and the detection limit (3.3 ?) at the modulation period of 30s is 0.52 ?mol dm(-3). Good recoveries around 100% have been obtained for phosphate ions spiked into real water samples. PMID:24274279

Ogusu, Takeshi; Uchimoto, Katsuya; Takeuchi, Masaki; Tanaka, Hideji

2014-01-01

216

Impairments in deeply-saturated optical parametric amplifiers for amplitude- and phase-modulated signals.  

Science.gov (United States)

We measure impairment of on-off-keyed and differential-phase-shift-keyed signals imposed by gain saturation in a fiber parametric amplifier. Phase modulation is observed to be more robust, particularly for deep (15 dB) saturation. PMID:19547239

Alic, N; Jopson, R M; Ren, J; Myslivets, E; Jiang, R; Gnauck, A H; Radic, S

2007-07-01

217

Dynamics of a nonlinear oscillator and a low-amplitude frequency-modulated wave  

International Nuclear Information System (INIS)

When the frequency of a small amplitude plane wave is varied slowly over a large enough bandwidth and this wave is incident upon a nonlinear oscillator, the resulting perturbed motion can exhibit stochastic behavior. Applications for the study of this system are wide and varied. We apply Lie-transform perturbation theory and mapping techniques in the analysis of the stochastic transition and the consequent induced diffusion in the oscillator phase space. A constant of the motion to the first order in a peturbation parameter is calculated, a mapping approximation is derived, and diffusion calculations from the mapping are given. Copyright 1987 Academic Press, Inc

218

Amplitude modulation for the Swift-Hohenberg and Kuramoto-Sivashinski equations  

Science.gov (United States)

Employing a harmonic balance technique inspired from the methods of Renormalization Group and Multiple Scales [R. E. O'Malley, Jr. and E. Kirkinis. "A combined renormalization group-multiple scale method for singularly perturbed problems," Stud. Appl. Math. 124(4), 383-410, (2010)], we derive the amplitude equations for the Swift-Hohenberg and Kuramoto-Sivashinski equations to arbitrary order in the context of roll patterns. This new and straightforward derivation improves previous attempts and can be carried-out with symbolic computation that minimizes effort and avoids error.

Kirkinis, Eleftherios; O'Malley, Robert E.

2014-12-01

219

One set of sounds, two tonotopic maps : exploring auditory cortex with amplitude-modulated tones  

OpenAIRE

Objective: The possibility of simultaneously observing activation of primary and secondary auditory cortices has been demonstrated by Engelien et al. [Hear Res 2000;148:153 60]. Methods: Such a dual monitoring by means of neuromagnetic recordings can be achieved when a subject is stimulated by brief pulses of 40 Hz-modulated tones. Depending on the frequency filter applied, either the steady-state field (SSF) or the N1m can be extracted from the evoked magnetic field complex. R...

Weisz, Nathan; Keil, Andreas; Wienbruch, Christian; Hoffmeister, S.; Elbert, Thomas

2004-01-01

220

Drug-induced immunophenotypic modulation in childhood ALL: implications for minimal residual disease detection.  

Science.gov (United States)

Assessment of minimal residual disease (MRD) by flow cytometry is considered to be based on the reproducibility of the leukemic immunophenotype detected at diagnosis. However, we previously noticed modulation of surface antigen expression in acute lymphoblastic leukemia (ALL) during the early treatment. Hence, we investigated this in 30 children with B-cell precursor ALL consecutively enrolled in the AIEOP-BFM ALL 2000 protocol. Quantitative expression of seven antigens useful in MRD monitoring was studied at diagnosis and compared to that measured at different time points of remission induction therapy. Downmodulation in the expression of CD10 and CD34 occurred at follow-up. By contrast, upmodulation of CD19, CD20, CD45RA, and CD11a was observed, while the expression of CD58 remained stable. Despite this, we could unambiguously discriminate leukemic cells from normal residual B cells. This holds true when bone marrow (BM) samples from similarly treated T-ALL patients, but not from healthy donors, were used as reference. Our results indicate that immunophenotypic modulation occurs in ALL during the early phases of BFM-type protocols. However, the accuracy of MRD detection by flow cytometry seems not negatively affected if adequate analysis protocols are employed. Investigators should take this phenomenon into account in order to avoid pitfalls in flow cytometric MRD studies. PMID:15538405

Gaipa, G; Basso, G; Maglia, O; Leoni, V; Faini, A; Cazzaniga, G; Bugarin, C; Veltroni, M; Michelotto, B; Ratei, R; Coliva, T; Valsecchi, M G; Biondi, A; Dworzak, M N

2005-01-01

221

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

222

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

Science.gov (United States)

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

Santos, Sergio; Verdaguer, Albert; Chiesa, Matteo

2012-07-01

223

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 occurs before the tip-sample contacts, and this motion signal can replace the sample-contact-signal to avoid destroying the sample. PMID:22778663

Shih, Po-Jen

2012-01-01

224

Cochlear tuning in the gerbil: a comparison of responses to sinusoidal amplitude modulation and difference tone stimuli.  

Science.gov (United States)

Vocalizations often have periodic variations of their acoustic waveform envelope. Two simultaneously presented frequencies have an envelope fluctuation with a frequency equal to their difference tone (DT = F2-F1). Sinusoidal amplitude modulation (SAM) of a carrier frequency also produces an envelope fluctuation. Electrical ensemble responses to DT and SAM stimuli were recorded from the gerbil's round window. The predominant frequency of the response to the DT stimuli is F2-F1; to the SAM stimuli, it is the modulation frequency. Both responses are spectrally, temporally, and dynamically non-linear. Forward masking of a low-frequency DT response produced a tuning curve (TC) with a tip at the high-stimulus frequency. Forward masker TCs of a low-frequency SAM ensemble response had tips at the high frequency of the carrier. Tip thresholds and sharpness of tuning of DT and SAM TCs are quite similar, with cochlear neurons having high characteristic frequencies providing sharply tuned information about low frequency acoustic envelope periodicities. PMID:9776203

Henry, K R

1998-01-01

225

Gas Phase Photoacoustic Sensor at 8.41 mu m Using Quartz Tuning Forks and Amplitude Modulated Quantum Cascade Lasers  

Energy Technology Data Exchange (ETDEWEB)

We demonstrate the performance of a novel long-wave infrared photoacoustic laser absorbance spectrometer for gas-phase species using an amplitude modulated (AM) quantum cascade (QC) laser and a quartz tuning fork microphone. Photoacoustic signal was generated by focusing the output of a Fabry-Perot QC laser operating at 8.41 ?m between the legs of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The QC laser was modulated at the resonant frequency of the tuning fork (32.8 kHz) and delivered a modest 5.3 mW at the tuning fork. This spectrometer was calibrated using the infrared absorber Freon-134a by performing a simultaneous absorption measurement using a 35 cm absorption cell. The NEAS of this instrument was determined to be 2 x 10{sup -8} W cm-1 Hz{sup -1/2}. A corresponding theoretical analysis of the instrument sensitivity is presented and is capable of quantitatively reproducing the experimental NEAS, indicating that the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.

Wojcik, Michael D.; Phillips, Mark C.; Cannon, Bret D.; Taubman, Matthew S.

2006-10-01

226

Noisy galvanic vestibular stimulation modulates the amplitude of EEG synchrony patterns.  

Science.gov (United States)

Noisy galvanic vestibular stimulation has been associated with numerous cognitive and behavioural effects, such as enhancement of visual memory in healthy individuals, improvement of visual deficits in stroke patients, as well as possibly improvement of motor function in Parkinson's disease; yet, the mechanism of action is unclear. Since Parkinson's and other neuropsychiatric diseases are characterized by maladaptive dynamics of brain rhythms, we investigated whether noisy galvanic vestibular stimulation was associated with measurable changes in EEG oscillatory rhythms within theta (4-7.5 Hz), low alpha (8-10 Hz), high alpha (10.5-12 Hz), beta (13-30 Hz) and gamma (31-50 Hz) bands. We recorded the EEG while simultaneously delivering noisy bilateral, bipolar stimulation at varying intensities of imperceptible currents - at 10, 26, 42, 58, 74 and 90% of sensory threshold - to ten neurologically healthy subjects. Using standard spectral analysis, we investigated the transient aftereffects of noisy stimulation on rhythms. Subsequently, using robust artifact rejection techniques and the Least Absolute Shrinkage Selection Operator regression and cross-validation, we assessed the combinations of channels and power spectral features within each EEG frequency band that were linearly related with stimulus intensity. We show that noisy galvanic vestibular stimulation predominantly leads to a mild suppression of gamma power in lateral regions immediately after stimulation, followed by delayed increase in beta and gamma power in frontal regions approximately 20-25 s after stimulation ceased. Ongoing changes in the power of each oscillatory band throughout frontal, central/parietal, occipital and bilateral electrodes predicted the intensity of galvanic vestibular stimulation in a stimulus-dependent manner, demonstrating linear effects of stimulation on brain rhythms. We propose that modulation of neural oscillations is a potential mechanism for the previously-described cognitive and motor effects of vestibular stimulation, and noisy galvanic vestibular stimulation may provide an additional non-invasive means for neuromodulation of functional brain networks. PMID:23874865

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

2013-01-01

227

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

228

Pressure and cold pain threshold in healthy subjects undergoing interferential current at different amplitude modulated frequencies / Avaliação do limiar de dor à pressão e ao frio em indivíduos saudáveis submetidos à corrente interferencial em diferentes frequências de amplitude modulada  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese JUSTIFICATIVA E OBJETIVOS: A corrente interferencial é um método de eletroestimulação bastante utilizado com finalidades analgésicas, porém, existem controvérsias com relação aos seus parâmetros de uso. O objetivo do estudo foi comparar diferentes frequências de amplitude modulada, da corrente inte [...] rferencial, sobre o limiar de dor à pressão e ao frio, em voluntários saudáveis. MÉTODOS: Trata-se de um ensaio cruzado, aleatório e com avaliadores e avaliados encobertos, de caráter quantitativo. Participaram deste estudo 20 voluntários subdivididos em quatro grupos, que durante quatro semanas passaram por diferentes frequências de amplitude modulada. Foram avaliados os limiares da dor à pressão e ao frio em quatro momentos distintos - no início, logo após eletroestimulação, 20 e 60 minutos após. Como forma de eletroestimulação foi utilizada a corrente interferencial nas frequências de amplitude modulada de 1Hz, 10Hz e 100Hz, com frequência de base de 4.000Hz, sendo que em uma determinada semana os voluntários recebiam placebo (0Hz). RESULTADOS: Não houve diferença significativa nas comparações dentro das frequências, nem entre elas e o grupo placebo. CONCLUSÃO: O uso da corrente interferencial nas frequências de amplitude modulada de 1Hz, 10Hz e 100Hz não produziu alterações nos limiares de dor ao frio e à pressão, semelhante ao encontrado para o grupo placebo. Abstract in english BACKGROUND AND OBJECTIVES: The interferential current is an electrical stimulation method widely used with analgesic purposes; however, there are controversies regarding their usage parameters. The aim of this study was to compare different amplitude modulated frequencies of the interferential curr [...] ent on the pressure and cold pain threshold in healthy volunteers. METHODS: This is a crossover, randomized and blinded evaluators and evaluated in quantitative character test. Participants were 20 volunteers divided into four groups, who for four weeks were subject to different modulated frequencies. Thresholds of pressure and cold pain in four different times were evaluated - at the beginning, right after electric stimulation, 20 and 60 minutes after. As a form of electrical stimulation, interferential current was used at modulated amplitude frequencies of 1Hz, 10Hz and 100Hz with base frequency of 4,000Hz, being that in a particular week volunteers received placebo (0Hz). RESULTS: There has been no significant difference in comparisons within frequencies or between them and the placebo group. CONCLUSION: The use of amplitude modulated frequencies of interferential current of 1Hz, 10Hz and 100Hz did not change cold and pressure pain thresholds, similar to what has been found for the placebo group

Alexandra de Oliveira, Claro; Bruna Akie, Kanezawa; Michele de, Camargo; Vanessa Maria, Paes; José Luiz Marinho, Portolez; Gladson Ricardo Flor, Bertolini.

2014-09-01

229

Identification of Functionally Relevant Lysine Residues That Modulate Human Farnesoid X Receptor Activation  

Science.gov (United States)

Base amino acid lysine residues play an important role in regulation of nuclear receptors [e.g., farnesyl X receptor (FXR)], leading to enhanced or suppressed biologic activity. To understand the molecular mechanisms and the subsequent effects in modulating FXR functions in diverse biologic processes, we individually replaced eight highly conserved lysine residues of human FXR (hFXR) with arginine. The effects of each mutated FXR on target gene activation, subcellular localization, protein-protein association, and protein-DNA interaction were investigated. Results demonstrated that K122R, K210R, K339R, and K460R mutants of hFXR significantly impaired target gene [organic solute transporter ?/? and bile salt export pump (BSEP)] promoter reporter activity in a ligand-dependent fashion. None of the four mutants affected the nuclear localization of FXR. Protein interaction studies show that K210R slightly but significantly decreased FXR/retinoid X receptor (RXR) binding affinity but enhanced the interaction of FXR with lysine methyltransferase Set7/9 by ?21%. K460R decreased the FXR interaction with Set7/9 by ?45% but had no significant effects on interaction with RXR. Electrophoretic mobility shift assays demonstrated that hFXR-K210R and -K339R reduced the protein-DNA (IR1 element at hBSEP promoter) binding affinity by ?80 and ?90%, respectively. Computational-based protein modeling studies were consistent with these results and provided further insights into the potential underlying mechanisms responsible for these results. In conclusion, four highly conserved lysine residues of hFXR, K122, K210, K339, and K460, have been identified that play a critical role in FXR target gene regulation and molecular interaction (protein-protein and protein-DNA). PMID:23462506

Luo, Yuhuan; Backos, Donald S.; Xu, Shuhua; Balasubramaniyan, Natarajan; Reigan, Philip; Suchy, Frederick J.

2013-01-01

230

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

Directory of Open Access Journals (Sweden)

Full Text Available An accurate ultrasonic range finder employing Sliding Discrete Fourier Transform (SDFT based restructured phase-locked loop (RPLL, which is an improved version of the recently proposed integrated phase-locking scheme (IPLL, has been expounded. This range finder principally utilizes amplitude-modulated ultrasonic waves assisted by an infrared (IR pilot signal. The phase shift between the envelope of the reference IR pilot signal and that of the received ultrasonic signal is proportional to the range. The extracted envelopes are filtered by SDFT without introducing any additional phase shift. A new RPLL is described in which the phase error is driven to zero using the quadrature signal derived from the SDFT. Further, the quadrature signal is reinforced by another cosine signal derived from a lookup table (LUT. The pulse frequency of the numerically controlled oscillator (NCO is extremely accurate, enabling fine tuning of the SDFT and RPLL also improves the lock time for the 50?Hz input signal to 0.04?s. The percentage phase error for the range 0.6?m to 6?m is about 0.2%. The VHDL codes generated for the various signal processing steps were downloaded into a Cyclone FPGA chip around which the ultrasonic ranger had been built.

P. A. Janakiraman

2010-01-01

231

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

Science.gov (United States)

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

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

2014-08-01

232

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

Science.gov (United States)

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

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

2014-08-22

233

Transient Nature of Argon and Molecular Gas-Seeded Argon Inductive Thermal Plasmas in Pulse Amplitude Modulation Approach  

Science.gov (United States)

In the present work, a high power (30kW), atmospheric pressure inductive thermal plasma has been diagnosed both theoretically and experimentally in pulse amplitude modulation approach with Ar, Ar-CO2, Ar-N2, and Ar-O2 as working gases (100lpm argon and 2.5lpm molecular gas). Simulation has been carried out using a two-dimensional local thermodynamic equilibrium (LTE) code for the same torch and operating conditions as that of experiment. Calculating the so-called response times from both simulated and experimental temporal radiation intensity of ArI at 751nm, a rigorous and comprehensive comparative discussion has been made for a shimmer current level (SCL), the ratio of lower to higher level of current pulse, varying from 40%—100%. The measured temperature is also compared with the calculated apparent temperature. In spite of some discrepancies (at lower SCL) with the magnitude of response times of experimental and simulated plasma at the instant of on-pulsing transition, similar trend of those have been observed. These results will help to clear the understanding of transient performance of the concerned gases and equilibrium phenomena.

Hossain, M. M.; Tanaka, Yasunori; Sakuta, Tadahiro

234

Characterization of a single molecular QCA cell by Q-control enhanced amplitude modulation atomic force microscopy  

International Nuclear Information System (INIS)

Major technical challenges for reduction of device sizes for computation and memory are the interconnection and power dissipation problems. Molecular quantum-dot cellular automata (QCA) have been proposed as solutions to this problem. Silicon phthalocyanine (SiPc) is a possible candidate for a molecular QCA element. Therefore, it is important to develop an in situ observation technique to visualize individual SiPc molecules. We report here the first image of a single SiPc dimer in air by using quality factor control (Q-control) enhanced amplitude modulation atomic force microscopy (AFM) and an investigation of the interaction forces between the tip and SiPc dimer. The AFM was operated at 0% relative humidity in an ultrapure nitrogen environment either with or without Q-control. Theoretical simulations using the point-mass description of the AFM, demonstrated that Q-enhancement reduced the force exerted from the tip to the sample surface. Our results, consistent with theory, demonstrated that the image force was reduced and a greater height and a larger size were measured. The advantages of this method can be extended to the AFM observation of other 'soft' structures, and these results can be useful for a wider community

235

Characterization of a single molecular QCA cell by Q-control enhanced amplitude modulation atomic force microscopy.  

Science.gov (United States)

Major technical challenges for reduction of device sizes for computation and memory are the interconnection and power dissipation problems. Molecular quantum-dot cellular automata (QCA) have been proposed as solutions to this problem. Silicon phthalocyanine (SiPc) is a possible candidate for a molecular QCA element. Therefore, it is important to develop an in situ observation technique to visualize individual SiPc molecules. We report here the first image of a single SiPc dimer in air by using quality factor control (Q-control) enhanced amplitude modulation atomic force microscopy (AFM) and an investigation of the interaction forces between the tip and SiPc dimer. The AFM was operated at 0% relative humidity in an ultrapure nitrogen environment either with or without Q-control. Theoretical simulations using the point-mass description of the AFM, demonstrated that Q-enhancement reduced the force exerted from the tip to the sample surface. Our results, consistent with theory, demonstrated that the image force was reduced and a greater height and a larger size were measured. The advantages of this method can be extended to the AFM observation of other "soft" structures, and these results can be useful for a wider community. PMID:16678348

Lee, I; Sarveswaran, V; Lieberman, M; Greenbaum, E

2006-01-01

236

Characterization of a single molecular QCA cell by Q-control enhanced amplitude modulation atomic force microscopy  

Energy Technology Data Exchange (ETDEWEB)

Major technical challenges for reduction of device sizes for computation and memory are the interconnection and power dissipation problems. Molecular quantum-dot cellular automata (QCA) have been proposed as solutions to this problem. Silicon phthalocyanine (SiPc) is a possible candidate for a molecular QCA element. Therefore, it is important to develop an in situ observation technique to visualize individual SiPc molecules. We report here the first image of a single SiPc dimer in air by using quality factor control (Q-control) enhanced amplitude modulation atomic force microscopy (AFM) and an investigation of the interaction forces between the tip and SiPc dimer. The AFM was operated at 0% relative humidity in an ultrapure nitrogen environment either with or without Q-control. Theoretical simulations using the point-mass description of the AFM, demonstrated that Q-enhancement reduced the force exerted from the tip to the sample surface. Our results, consistent with theory, demonstrated that the image force was reduced and a greater height and a larger size were measured. The advantages of this method can be extended to the AFM observation of other 'soft' structures, and these results can be useful for a wider community.

Lee, I. [Department of Electrical and Computer Engineering, University of Tennessee, TN 37996-2100 (United States)]. E-mail: leei@ornl.gov; Sarveswaran, V. [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Lieberman, M. [Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Greenbaum, E. [Oak Ridge National Laboratory, Chemical Science Division, Oak Ridge, TN 37831-6194 (United States)

2006-06-15

237

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-01

238

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

International Nuclear Information System (INIS)

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

239

Stochastic amplitude-modulated stretching of rabbit flexor digitorum profundus tendons reduces stiffness compared to cyclic loading but does not affect tenocyte metabolism  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background It has been demonstrated that frequency modulation of loading influences cellular response and metabolism in 3D tissues such as cartilage, bone and intervertebral disc. However, the mechano-sensitivity of cells in linear tissues such as tendons or ligaments might be more sensitive to changes in strain amplitude than frequency. Here, we hypothesized that tenocytes in situ are mechano-responsive to random amplitude modulation of strain. Methods We compared stochastic amplitude-modulated versus sinusoidal cyclic stretching. Rabbit tendon were kept in tissue-culture medium for twelve days and were loaded for 1h/day for six of the total twelve culture days. The tendons were randomly subjected to one of three different loading regimes: i stochastic (2 – 7% random strain amplitudes, ii cyclic_RMS (2–4.42% strain and iii cyclic_high (2 - 7% strain, all at 1 Hz and for 3,600 cycles, and one unloaded control. Results At the end of the culture period, the stiffness of the “stochastic” group was significantly lower than that of the cyclic_RMS and cyclic_high groups (both, p Conclusions We conclude that, despite an equivalent metabolic response, stochastically stretched tendons suffer most likely from increased mechanical microdamage, relative to cyclically loaded ones, which is relevant for tendon regeneration therapies in clinical practice.

Steiner Thomas H

2012-11-01

240

Interplay between amino acid residues at positions 192 and 115 in modulating hydrolytic activities of human paraoxonase 1.  

Science.gov (United States)

Human paraoxonase 1 (h-PON1) is a Ca(2+)-dependent serum enzyme that catalyzes the hydrolysis of different types of substrates. The crystal structure of h-PON1 is not solved yet and the molecular details of how the enzyme catalyzes different types of reactions are not clear. Literature suggests that the amino acid residues at positions 192 and 115 are important for various hydrolytic activities of h-PON1. It is proposed that catalytic residue H115 (and H134) mediates the lactonase and the arylesterase activities of the enzyme while the amino acid residue at position 192 modulates various other hydrolytic activities of the enzyme. However, the relationship between these two residues in the hydrolytic activities of h-PON1 is not studied in detail. In this study, we have expressed and purified the wild-type recombinant h-PON1 (rh-PON1(wt)) and its point mutants differing in the amino acid residues at positions 192 and/or 115 using an Escherichia coli expression system. The hydrolytic activities of the purified enzymes were compared using enzymatic assays. Our results, for the first time, show that (a) the presence of a particular amino acid residue at position 192 differentially alters the effect of the H115W substitution, and (b) H115 residue is not always needed for the lactonase and arylesterase activities of the enzyme. The results also suggest that the amino acid residues at position 192 and 115 act in conjunction in modulating the hydrolytic activities of the enzyme. PMID:25107406

Bajaj, Priyanka; Aggarwal, Geetika; Tripathy, Rajan K; Pande, Abhay H

2014-10-01

241

Reconstructing 3-D maps of the local viscoelastic properties using a finite-amplitude modulated radiation force.  

Science.gov (United States)

A modulated acoustic radiation force, produced by two confocal tone-burst ultrasound beams of slightly different frequencies (i.e. 2.0 MHz ± ?f/2, where ?f is the difference frequency), can be used to remotely generate modulated low-frequency (?f ? 500 Hz) shear waves in attenuating media. By appropriately selecting the duration of the two beams, the energy of the generated shear waves can be concentrated around the difference frequency (i.e., ?f ± ?f/2). In this manner, neither their amplitude nor their phase information is distorted by frequency-dependent effects, thereby, enabling a more accurate reconstruction of the viscoelastic properties. Assuming a Voigt viscoelastic model, this paper describes the use of a finite-element-method model to simulate three-dimensional (3-D) shear-wave propagation in viscoelastic media containing a spherical inclusion. Nonlinear propagation is assumed for the two ultrasound beams, so that higher harmonics are developed in the force and shear spectrum. Finally, an inverse reconstruction algorithm is used to extract 3-D maps of the local shear modulus and viscosity from the simulated shear-displacement fields based on the fundamental and second-harmonic component. The quality of the reconstructed maps is evaluated using the contrast between the inclusion and the background and the contrast-to-noise ratio (CNR). It is shown that the shear modulus can be accurately reconstructed based on the fundamental component, such that the observed contrast deviates from the true contrast by a root-mean-square-error (RMSE) of only 0.38 and the CNR is greater than 30 dB. If the second-harmonic component is used, the RMSE becomes 1.54 and the corresponding CNR decreases by approximately 10-15 dB. The reconstructed shear viscosity maps based on the second harmonic are shown to be of higher quality than those based on the fundamental. The effects of noise are also investigated and a fusion operation between the two spectral components is applied to enhance the reconstruction quality. Finally, a modified shear-wave spectroscopy technique, shown to be more robust to noise, is described for the estimation of the viscoelastic properties inside and outside the spherical inclusion under conditions of increased noise. PMID:24011778

Giannoula, Alexia; Cobbold, Richard; Bezerianos, Anastasios

2014-02-01

242

Amplitude modulation dynamic force microscopy imaging in liquids with atomic resolution: comparison of phase contrasts in single and dual mode operation  

International Nuclear Information System (INIS)

We present a systematic analysis of the atomic-scale imaging capabilities for mineral surfaces in a liquid environment in single and dual mode amplitude modulation dynamic force microscopy. To study the difference in sensitivity between the first and second eigenmode phase signals we investigate the observed atomic-scale contrasts of the mica–water interface under varying imaging conditions. For this purpose, we systematically change the main imaging parameters including the setpoint amplitude of the imaging feedback, the free oscillation amplitudes of the first and second flexural eigenmodes, and their ratio. This allows for an in-depth analysis of the sensitivities of the first and second eigenmode phase signals to draw conclusions regarding the underlying physical mechanisms and the interpretation of the contrast in the multi-frequency technique. (paper)

243

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

OpenAIRE

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

Balin?ski, A.

2013-01-01

244

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

Directory of Open Access Journals (Sweden)

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

245

Tuberoinfundibular peptide of 39 residues (TIP39) signaling modulates acute and tonic nociception.  

Science.gov (United States)

Tuberoinfundibular peptide of 39 residues (TIP39) synthesizing neurons at the caudal border of the thalamus and in the lateral pons project to areas rich in its receptor, the parathyroid hormone 2 receptor (PTH2R). These areas include many involved in processing nociceptive information. Here we examined the potential role of TIP39 signaling in nociception using a PTH2R antagonist (HYWH) and mice with deletion of TIP39's coding sequence or PTH2R null mutation. Intracerebroventricular (icv) infusion of HYWH significantly inhibited nociceptive responses in tail-flick and hot-plate tests and attenuated the nociceptive response to hindpaw formalin injection. TIP39-KO and PTH2R-KO had increased response latency in the 55°C hot-plate test and reduced responses in the hindpaw formalin test. The tail-flick test was not affected in either KO line. Thermal hypoalgesia in KO mice was dose-dependently reversed by systemic administration of the cannabinoid receptor 1 (CB1) antagonist rimonabant, which did not affect nociception in wild-type (WT). Systemic administration of the cannabinoid agonist CP 55,940 did not affect nociception in KO mice at a dose effective in WT. WT mice administered HYWH icv, and both KOs, had significantly increased stress-induced analgesia (SIA). Rimonabant blocked the increased SIA in TIP39-KO, PTH2R-KO or after HYWH infusion. CB1 and FAAH mRNA were decreased and increased, respectively, in the basolateral amygdala of TIP39-KO mice. These data suggest that TIP39 signaling modulates nociception, very likely by inhibiting endocannabinoid circuitry at a supraspinal level. We infer a new central mechanism for endocannabinoid regulation, via TIP39 acting on the PTH2R in discrete brain regions. PMID:20696160

Dimitrov, Eugene L; Petrus, Emily; Usdin, Ted B

2010-11-01

246

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

International Nuclear Information System (INIS)

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

247

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

248

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

CERN Document Server

The amplitude V_0 of unidirectional periodic potential modulation introduced by a surface grating into a two-dimensional electron gas (2DEG) formed at AlGaAs/GaAs heterointerface is measured as a function of electron density n_e by analyzing commensurability oscillation of the magnetoresistance. The electron density is varied either by applying a bias to a metallic back gate or by illumination. The amplitude decreases with increasing density, with the rate |dV_0/dn_e| roughly an order of magnitude larger for the former method. The result is interpreted in terms of the rate, dE_1/d(delta E_c), of the change in the first subband level E_1 in response to the variation of the conduction-band edge delta E_c above the heterointerface. The rate crucially depends on the thickness of the 2DEG.

Endo, A; Endo, Akira; Iye, Yasuhiro

2005-01-01

249

Cross polarization with phase and amplitude modulation of radio frequency fields in NMR-experiments with sample rotation at magic angle  

International Nuclear Information System (INIS)

One analyzes cross polarization of nuclei within a rotating system of coordinates as applied to the NMR-experiments with a specimen rotation under the magic angle. One worded a concept of simultaneous phase and amplitude modulation according to which the Hamiltonian form of the restored dipole interaction persisted if inversion of difference of radiofrequency field amplitudes occurred simultaneously with phase inversion. One presents a theoretical substantiation in terms of the average Hamiltonian theory. The concept is demonstrated both experimentally and by means of numerical analysis for a number of special cases. Phase periodic inversion in cross polarized experiments is shown to result into practically important advantage of suppression of interactions of chemical shift and influence of effects of coarse adjustment of radiofrequency field parameters

250

Song Amplitude of Rival Males Modulates the Territorial Behaviour of Great Tits During the Fertile Period of Their Mates  

OpenAIRE

Bird song is a widely used model in the study of sexual selection. Variation in the expression of sexually selected traits is thought to reflect variation in male genetic and/or phenotypic quality. Vocal amplitude is a song parameter that has received little attention in the context of sexual selection, but there is some evidence that the intensity of bird song affects female preferences. Here, we tested whether the amplitude of broadcast song plays a role in male–male competition. We used ...

Ritschard, M.; Oers, K.; Naguib, M.; Brumm, H.

2012-01-01

251

Fiber-wireless integration for 80 Gb/s dual-polarization-16 quadrature-amplitude-modulation signal transmission at Q-band  

Science.gov (United States)

We experimentally demonstrate a Q-band seamlessly integrated fiber-wireless system, where 80 Gb/s dual-polarization (DP) 16 quadrature-amplitude-modulation (DP-16QAM) is transmitted over 50-km single-mode fiber-28 (SMF-28) wire link, 0.5-m 2×2 multiple-input multiple-output wireless link, and finally, another 50-km SMF-28 wire link. Conventional multimodulus-algorithm equalization is introduced at the receiver to realize polarization demultiplexing and to minimize crosstalk between the two polarizations. For the first time, we realize fiber-wireless integration signal transmission with high-order modulation (16QAM) and polarization multiplexing at Q-band.

Zhao, Lun; Yu, Jianguo; Chen, Lei; Shen, Jie

2014-10-01

252

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

Directory of Open Access Journals (Sweden)

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

Jingjing Wang

2011-07-01

253

Point-by-point inscription of phase-shifted fiber Bragg gratings with electro-optic amplitude modulated femtosecond laser pulses.  

Science.gov (United States)

Femtosecond laser pulses were used for the direct point-by-point inscription of phase-shifted fiber Bragg gratings (FBGs) in a single fabrication step without postprocessing. An electro-optic amplitude modulator is used in the setup to generate a defined delay between two identical laser pulse trains for the grating inscription. The grating structure with a central phase shift is formed by focusing the modulated laser pulses into the core of a fiber, while the fiber is translated with a constant velocity. The induced phase shift leads to a narrow transmission band with a bandwidth considerably below 10 pm within the stop band of the FBG. The inscribed FBGs show a birefringence of 3.9×10(-5) whereas their temperature and strain sensitivities are 10.4??pm/K and 1.4??pm/?strain, respectively. The fabrication process is fast and offers a high grade of flexibility for the control of all grating parameters. PMID:24487860

Burgmeier, Jörg; Waltermann, Christian; Flachenecker, Günter; Schade, Wolfgang

2014-02-01

254

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

Science.gov (United States)

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

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

2012-11-01

255

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

Science.gov (United States)

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

Seçilmi?, M A; Özü, Ö Y; K?ro?lu, O E; ?ingirik, E; Büyükaf?ar, K

2014-11-01

256

Canine distemper virus envelope protein interactions modulated by hydrophobic residues in the fusion protein globular head.  

Science.gov (United States)

Membrane fusion for morbillivirus cell entry relies on critical interactions between the viral fusion (F) and attachment (H) envelope glycoproteins. Through extensive mutagenesis of an F cavity recently proposed to contribute to F's interaction with the H protein, we identified two neighboring hydrophobic residues responsible for severe F-to-H binding and fusion-triggering deficiencies when they were mutated in combination. Since both residues reside on one side of the F cavity, the data suggest that H binds the F globular head domain sideways. PMID:25355896

Avila, Mislay; Khosravi, Mojtaba; Alves, Lisa; Ader-Ebert, Nadine; Bringolf, Fanny; Zurbriggen, Andreas; Plemper, Richard K; Plattet, Philippe

2015-01-15

257

Amplitude Modulation Approach for Real-Time Algorithms of ECG-Derived Respiration / Desarrollo de Algoritmos en Tiempo Real para Derivar la Respiración del ECG Bajo el Criterio de Amplitud Modulada  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish Este trabajo presenta una metodología para la extracción de la actividad respiratoria derivada de un ECG (EDR, por sus siglas en ingles), basado en el enfoque de amplitud modulada (AM). Esto permite redefinir las metodologías actuales para obtener una señal EDR más continua, con altos factores de co [...] rrelación y un retraso menor entre la EDR y la actividad respiratoria. Se implementaron dos algoritmos: uno utilizando la modulación de la amplitud del pico R (EDRAM) y el otro aplicando un filtro paso-banda en el espectro de frecuencia de la respiración. A diferencia de otros trabajos en la literatura, se utilizan filtros convencionales de bajo orden pero sin sacrificar el factor de correlación (0.76 y 0.67) y manteniendo un retardo de ?0.27s (con EDRAM) en un ciclo de ?6s. Se realizó una prueba de robustez, donde se muestra una tolerancia a ruido blanco de hasta un 20% del valor máximo antes de que el factor de correlación bajara considerablemente. El algoritmo EDRAM se aplicó con éxito en un prototipo de sistema portable. Las dos metodologías propuestas muestran ventajas como el procesamiento en tiempo real y robustez bajo ciertos ruidos. La perspectiva de AM propuesta soporta el uso de ambos algoritmos para aplicaciones típicas con alta eficiencia, bajo costo computacional y facilidad de implementación. Estas características hacen que esta técnica facilite el desarrollo de sistemas portátiles, así como para incrementar la información de las bases de datos actuales. Abstract in english This work presents the development of an ECG-Derived Respiration (EDR) methodology based on the amplitude modulation approach. It allows to redefine actual methodologies in order to obtain a continuous EDR signals with high correlations and small delay between EDR and respiration activity. Two algor [...] ithms are implemented: one of them using the amplitude modulation of the R-peak (EDRAM) and another one applying a band-pass filter in the bandwidth of respiration. Unlike other techniques in literature, conventional low order filters are applied without sacrifice of correlation factor (0.76 and 0.67) and a minimum delay of 0.27s (with EDRAM) in a ?6s cycle. A robustness test was performed, and it shows a noise tolerance of up to 20% of the maximum value before its correlation factor drops considerably. The application into a wearable sensor was successfully implemented. The two methodologies proposed show advantages like real-time processing and robustness under certain noises. The proposed AM perspective supports the use of both algorithms for typical applications with high efficiency, low computational cost and ease of implementation. These characteristics result on a technique that facilitates the development of wearable systems, and to increase the information of actual databases.

J.L., Vargas-Luna; W., Mayr; J.A., Cortés-Ramírez.

258

An atypical residue in the pore of Varroa destructor GABA-activated RDL receptors affects picrotoxin block and thymol modulation  

Science.gov (United States)

GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using two electrode voltage clamp electrophysiology we show that one substitution (T6?M) ablates picrotoxin inhibition and increases the potency of GABA. This mutation also alters the effect of thymol, which enhances both insect and mammalian GABA responses, and is widely used as a miticide. Thymol decreases the GABA EC50 of WT receptors, enhancing responses, but in T6?M-containing receptors it is inhibitory. The other 3 atypical residues have no major effects on either the GABA EC50, the picrotoxin potency or the effect of thymol. In conclusion we show that the RDL 6? residue is important for channel block, activation and modulation, and understanding its function also has the potential to prove useful in the design of Varroa-specific insecticidal agents. PMID:25460510

Price, Kerry L.; Lummis, Sarah C.R.

2014-01-01

259

An atypical residue in the pore of Varroa destructor GABA-activated RDL receptors affects picrotoxin block and thymol modulation.  

Science.gov (United States)

GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using two electrode voltage clamp electrophysiology we show that one substitution (T6'M) ablates picrotoxin inhibition and increases the potency of GABA. This mutation also alters the effect of thymol, which enhances both insect and mammalian GABA responses, and is widely used as a miticide. Thymol decreases the GABA EC50 of WT receptors, enhancing responses, but in T6'M-containing receptors it is inhibitory. The other 3 atypical residues have no major effects on either the GABA EC50, the picrotoxin potency or the effect of thymol. In conclusion we show that the RDL 6' residue is important for channel block, activation and modulation, and understanding its function also has the potential to prove useful in the design of Varroa-specific insecticidal agents. PMID:25460510

Price, Kerry L; Lummis, Sarah C R

2014-10-18

260

Self-similarities in the frequency-amplitude space of a loss-modulated CO$_2$ laser  

OpenAIRE

We show the standard two-level continuous-time model of loss-modulated CO$_2$ lasers to display the same regular network of self-similar stability islands known so far to be typically present only in discrete-time models based on mappings. For class B laser models our results suggest that, more than just convenient surrogates, discrete mappings in fact could be isomorphic to continuous flows.

Bonatto, Cristian; Garreau, Jean Claude; Gallas, Jason A. C.

2005-01-01

261

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

262

Modulation of gamma and theta spectral amplitude and phase synchronization is associated with the development of visuo-motor learning  

OpenAIRE

The formation of new motor memories, which is fundamental for efficient performance during adaptation to a visuo-motor rotation, occurs when accurate planning is achieved mostly with feedforward mechanisms. The dynamics of brain activity underlying the switch from feedback to feedforward control is still matter of debate. Based upon the results of studies in declarative learning, it is likely that phase synchronization of low and high frequencies as well as their temporal modulation in power ...

Perfetti, Bernardo; Moisello, Clara; Landsness, Eric Carl; Kvint, Svetlana; Lanzafame, Simona; Onofrj, Marco; Di Rocco, Alessandro; Tononi, Giulio; Ghilardi, M. Felice

2011-01-01

263

Recording weak absorption spectra by the phase-shift method with deep amplitude and frequency modulation using a diode laser and a high Q cavity  

International Nuclear Information System (INIS)

A method is suggested and developed for recording absorption spectra of particles in a high Q cavity from the phase delay of amplitude-modulated radiation generated by a tunable diode laser. The method features high spectral resolution and sensitivity. It is based on the experimentally established possibility of recording spectra in conditions of high-percentage modulation, under which the concomitant frequency deviation exceeds the bandwidth. This is achieved by processing in a special way the signals in the absorption recording channel of the spectrometer and concurrently measuring the radiation frequency variation parameters in real time. The method is experimentally implemented for the case of square-pulse modulation of the laser injection current. The absorption spectrum of water molecules is recorded in the region of 644 nm with a spectral resolution of 4.5 × 10?3 cm?1 and a sensitivity of ?7 × 10?11 cm?1 in terms of the absorption coefficient. Comparative measurements are taken by another well-known high-sensitivity laser technique ICOS. The broadening coefficients for some weak absorption water lines by helium are determined. Possible ways are discussed of further development of the method suggested. (paper)

264

Blind polarization demultiplexing for quadrature amplitude modulation coherent optical communication systems using low-complexity and fast-converging independent component analysis  

Science.gov (United States)

A kind of blind polarization demultiplexing algorithm based on low-complexity and fast-converging independent component analysis (ICA) for quadrature amplitude modulation (QAM) coherent optical communications systems is proposed. The polarization demultiplexing is achieved by maximizing the signal's non-Gaussianity measured by the information theoretic quantity of negentropy. We demonstrate that some approximate nonlinear functions can be substituted for the negentropy and this greatly reduces the computational complexity. An adaptive gradient optimization algorithm and a fast-converging quasi-Newton algorithm are employed to maximize the negentropy. The numerical simulation and experimental results for polarization division multiplexing quadrature phase shift keying/16QAM without neglecting polarization mode dispersion reveal that the proposed ICA demultiplexing algorithms are feasible and effective for coherent optical receivers.

Tang, Jin; He, Jing; Xiao, Jiangnan; Chen, Lin

2014-05-01

265

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

266

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

Science.gov (United States)

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

Mori, Yojiro; Zhang, Chao; Kikuchi, Kazuro

2012-11-19

267

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

Science.gov (United States)

We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.

Zhang, Jie-Fang; Li, Yi-Shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.

2010-09-01

268

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

Science.gov (United States)

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.

Sinha, A. K.; Pathan, B. M.; Rajaram, R.; Rao, D. R. K.

2002-01-01

269

Immune Modulation of Minimal Residual Disease in Early Chronic Phase Chronic Myelogenous Leukemia  

Science.gov (United States)

BACKGROUND Most patients with chronic myelogenous leukemia (CML) harbor residual disease, as evidenced by molecular techniques even after treatment with high-dose imatinib (ie, 800 mg/d). Interferon alpha (IFN ?) is efficacious in CML likely due to its immunomodulatory properties, and is synergistic in vitro with imatinib and granulocyte macrophage-colony stimulating factor (GM-CSF). METHODS A study was undertaken to determine whether adding pegylated (PEG) IFN ?-2b and GM-CSF to high-dose imatinib may improve the complete molecular response rate in patients with CML in chronic phase. Ninety-four patients were treated with imatinib 800 mg/d for the first 6 months, then randomly assigned to continue high-dose imatinib alone (n = 49) or in combination with PEG IFN ?-2b 0.5 µg/kg/wk and GM-CSF 125 mg/m2 3× weekly (n = 45). RESULTS The median follow-up for all patients was 54 months (range, 7–70 months). There were no differences in the rates of complete cytogenetic response (87% vs 90%; P = 1.0), or of major (77% vs 77%; P = 1.0) or complete (11% vs 13%; P = 1.0) molecular response (on the international scale) at 12 months between the 2 arms, or at any time during the study. Adverse events led to PEG IFN ?-2b discontinuation in all patients. CONCLUSIONS The addition of PEG IFN ?-2b and GM-CSF to high-dose imatinib therapy does not improve significantly the cytogenetic or molecular response rates compared with high-dose imatinib alone. The high dropout rate in the PEG IFN ?-2b arm may have compromised its potential immunomodulatory benefit. PMID:20886606

Cortes, Jorge; Quintás-Cardama, Alfonso; Jones, Dan; Ravandi, Farhad; Garcia-Manero, Guillermo; Verstovsek, Srdan; Koller, Charles; Hiteshew, Jody; Shan, Jenny; O’Brien, Susan; Kantarjian, Hagop

2015-01-01

270

N-terminal tyrosine residues within the potassium channel Kir3 modulate GTPase activity of Galphai.  

Science.gov (United States)

trkB activation results in tyrosine phosphorylation of N-terminal Kir3 residues, decreasing channel activation. To determine the mechanism of this effect, we reconstituted Kir3, trkB, and the mu opioid receptor in Xenopus oocytes. Activation of trkB by BDNF (brain-derived neurotrophic factor) accelerated Kir3 deactivation following termination of mu opioid receptor signaling. Similarly, overexpression of RGS4, a GTPase-activating protein (GAP), accelerated Kir3 deactivation. Blocking GTPase activity with GTPgammaS also prevented Kir3 deactivation, and the GTPgammaS effect was not reversed by BDNF treatment. These results suggest that BDNF treatment did not reduce Kir3 affinity for Gbetagamma but rather acted to accelerate GTPase activity, like RGS4. Tyrosine phosphatase inhibition by peroxyvanadate pretreatment reversibly mimicked the BDNF/trkB effect, indicating that tyrosine phosphorylation of Kir3 may have caused the GTPase acceleration. Tyrosine to phenylalanine substitution in the N-terminal domain of Kir3.4 blocked the BDNF effect, supporting the hypothesis that phosphorylation of these tyrosines was responsible. Like other GAPs, Kir3.4 contains a tyrosine-arginine-glutamine motif that is thought to function by interacting with G protein catalytic domains to facilitate GTP hydrolysis. These data suggest that the N-terminal tyrosine hydroxyls in Kir3 normally mask the GAP activity and that modification by phosphorylation or phenylalanine substitution reveals the GAP domain. Thus, BDNF activation of trkB could inhibit Kir3 by facilitating channel deactivation. PMID:12082117

Ippolito, Danielle L; Temkin, Paul A; Rogalski, Sherri L; Chavkin, Charles

2002-09-01

271

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

International Nuclear Information System (INIS)

To determine whether residual interfraction seminal vesicle (SV) displacement necessitates specific planning target volume (PTV) margins during fiducial-guided intensity modulated radiation therapy (IMRT) of the prostate. A planning computed tomography (CT) scan and 2 subsequent CT scans were prospectively obtained for 20 prostate cancer patients with intraprostatic fiducial markers. After CT registration, SV displacement relative to the prostate was quantified as a function of margin size for both the proximal (1 cm) SV (PSV) and the full SV (FSV). Two IMRT plans were simulated for each patient (prostate + PSV and prostate + FSV) both with a uniform 5-mm PTV margin. Minimum clinical target volume (CTV) dose (Dmin) and the volume of SV receiving 95% of the prescription dose (V95%) were assessed during treatment and compared with the initial plan. In all cases, SV displacement with respect to the prostate was greater for the FSV compared with the PSV. To ensure at least 95% geometrical coverage of the CTV for 90% of patients, margins of 5 and 8 mm were required for the PSV and FSV, respectively. Dosimetrically, residual SV displacement had minimal impact on PSV coverage compared with FSV coverage. For the PSV Dmin was ?95% of the prescribed dose in 90% of patients with an overall mean V95% of 99.6 ± 0.8%; for the FSV Dmin was ?95% of the prescribed dose in only 45% of patients with a mean V95% of 97nts with a mean V95% of 97.9 ± 2.4%. The SVs move differentially from the prostate and exhibit greater variation with increasing distance from the prostate. For plans targeting just the prostate and PSVs, 5-mm PTV expansions are adequate. However, despite daily localization of the prostate, larger PTV margins are required for cases where the intent is to completely cover the FSV.

272

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

International Nuclear Information System (INIS)

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

273

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

Energy Technology Data Exchange (ETDEWEB)

In this study, atomic force microscopy (AFM) has been employed to image a photopolymerized poly(ethylene glycol) diacrylate (PEG-DA) hydrogel. The same area was imaged both in amplitude modulation (AM) and in frequency modulation (FM) mode and the latter allowed for excellent resolution of the hydrogel microstructure. It shows globular domains with typical diameters in the range of ?10–100 nm. The hydrogel morphology has been analysed using grain size analysis as well as roughness analysis. Based on AFM topography images of hydrogel nano-domains, a set of roughness parameters has been identified which can be readily used as descriptors for spatial resolution. It includes the density of summits, S{sub ds}, the mean summit curvature, S{sub sc}, the surface area ratio, S{sub dr}, and the correlation length parameter, S{sub cl37}. The latter describes the length over which the autocorrelation function decays to 37% of its peak value. These parameters allow for better discrimination than the widely used root-mean-square (RMS) roughness, S{sub q}, and are available with common image processing software packages. Systematic variation of the virtual tilt angle has indicated that these parameters are robust to small variations in plane levelling. Such image processing is frequently needed to separate the inherent surface microstructure from the global topography related to sample tilt or surface waviness. Hydrogels are an important group of biomaterials as they find numerous applications in biomedical engineering, ranging from adhesives, to controlled release of water-soluble drugs, to encapsulation of cells, to tissue engineering. Optimisation of their interactions with bioentities, such as bacteria, cells or proteins, requires accurate surface characterisation.

Munz, M., E-mail: martin.munz@npl.co.uk

2013-08-15

274

Design, study, and achievement of a fiber optic amplitude modulation sensor for angular position detection: application to an automotive steering sytem  

Science.gov (United States)

The reliable, accurate and low cost measurement of angular position is an important challenge for numerous industries such as aerospace or automotive industries. We propose a new optical fiber angular position sensor connected to an automotive power steering column. This sensor allows the measurement of the angular position of a car steering wheel over a large range (+/- 3 turns of wheel). The wheel rotation induces micro-bending in the transducer part of the optical fiber sensing system. This system operates as an amplitude modulation sensor based on mode coupling in the transducing fiber in the case when all the modes are equally excited. We study the sensor's response both theoretically and experimentally with a multimode step index optical fiber [Rf (fiber radius) = 300?m rc (core radius) = 50?m nc (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632, 8 nm at the ambient Temperature (20°C)]. This sensor has been tested between (-3x360) and (+3x360) degrees with 0,147 sensitivity. We show that the sensitivity can be controlled as a function of the sensor's length and the study of the sensor's output power as a function of the angular position has been achieved. We compare modeling and experimental validation and we conclude by a perspective of what could be soon an industrial sensor.

Javahiraly, Nicolas; Perrotton, Cédric; Chakari, Ayoub; Meyrueis, Patrick

2009-05-01

275

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

DEFF Research Database (Denmark)

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

Hancke, Kasper; Hancke, Torunn

2008-01-01

276

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

277

Scattering Amplitudes  

CERN Document Server

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

Elvang, Henriette

2013-01-01

278

Growth of pentacene on parylene and on BCB for organic transistors application, and DNA-based nanostructures studied by Amplitude : Modulation Atomic Force Microscopy in air and in liquids  

OpenAIRE

This work reports the various aspects of the application of atomic force microscopy (AFM), for the characterization of organic semiconductors and DNA-based arrays, for organic electronics and biological applications. On these soft surfaces, the amplitude modulation AFM mode was chosen. This choice is argued by a study of dissipative processes, performed on a particular sample, a DNA chip. We showed the influence of experimental parameters on the topographic and phase image quality. By calcula...

Iazykov, Maksym

2011-01-01

279

A model of anuran auditory periphery reveals frequency-dependent adaptation to be a contributing mechanism for two-tone suppression and amplitude modulation coding.  

Science.gov (United States)

Anuran auditory nerve fibers (ANF) tuned to low frequencies display unusual frequency-dependent adaptation which results in a more phasic response to signals above best frequency (BF) and a more tonic response to signals below. A network model of the first two layers of the anuran auditory system was used to test the contribution of this dynamic peripheral adaptation on two-tone suppression and amplitude modulation (AM) tuning. The model included a peripheral sandwich component, leaky-integrate-and-fire cells and adaptation was implemented by means of a non-linear increase in threshold weighted by the signal frequency. The results of simulations showed that frequency-dependent adaptation was both necessary and sufficient to produce high-frequency-side two-tone suppression for the ANF and cells of the dorsal medullary nucleus (DMN). It seems likely that both suppression and this dynamic adaptation share a common mechanism. The response of ANFs to AM signals was influenced by adaptation and carrier frequency. Vector strength synchronization to an AM signal improved with increased adaptation. The spike rate response to a carrier at BF was the expected flat function with AM rate. However, for non-BF carrier frequencies the response showed a weak band-pass pattern due to the influence of signal sidebands and adaptation. The DMN received inputs from three ANFs and when the frequency tuning of inputs was near the carrier, then the rate response was a low-pass or all-pass shape. When most of the inputs were biased above or below the carrier, then band-pass responses were observed. Frequency-dependent adaptation enhanced the band-pass tuning for AM rate, particularly when the response of the inputs was predominantly phasic for a given carrier. Different combinations of inputs can therefore bias a DMN cell to be especially well suited to detect specific ranges of AM rates for a particular carrier frequency. Such selection of inputs would clearly be advantageous to the frog in recognizing distinct spectral and temporal parameters in communication calls. PMID:21565263

Wotton, J M; Ferragamo, M J

2011-10-01

280

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

CERN Document Server

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

Danilov, G S

2003-01-01

281

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

OpenAIRE

Widely spread cruel misconceptions and mistakes in the calculation of multi-loop superstring amplitudes are exposed. Correct calculations are given. It is shown that the cardinal mistake in the gauge fixing procedure presents ab ovo in the Verlinde papers. The mistake was reproduced in following proposals including the recent papers. The modular symmetry of the multi-loop superstring amplitudes is clarified, an incorrectness of previous conjectures being shown. It is shown t...

Danilov, G. S.

2003-01-01

282

Finite amplitude envelope surface solitons  

International Nuclear Information System (INIS)

Known results on the nonlinear coupling of surface plasma waves with quasistationary ion density perturbations are generalized to include finite amplitude density modulations. A more rigorous analytical criterion is provided for the existence of the surface soliton, by using the pseudopotential formalism. Finite amplitude solutions are obtained numerically and their characteristics are discussed. The present results are useful in understanding the nonlinear dynamics and the periodic oscillatory structures on plasma surfaces

283

N-terminal Tyrosine Residues within the Potassium Channel Kir3 Modulate GTPase Activity of G?i*  

OpenAIRE

trkB activation results in tyrosine phosphorylation of N-terminal Kir3 residues, decreasing channel activation. To determine the mechanism of this effect, we reconstituted Kir3, trkB, and the mu opioid receptor in Xenopus oocytes. Activation of trkB by BDNF (brain-derived neurotrophic factor) accelerated Kir3 deactivation following termination of mu opioid receptor signaling. Similarly, overexpression of RGS4, a GTPase-activating protein (GAP), accelerated Kir3 deactivation. Blocking GTPase a...

Ippolito, Danielle L.; Temkin, Paul A.; Rogalski, Sherri L.; Chavkin, Charles

2002-01-01

284

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

DEFF Research Database (Denmark)

Aquaporin 4 (AQP4) is the predominant water channel in the mammalian brain and is mainly expressed in the perivascular glial endfeet at the brain-blood interface. AQP4 serves as a water entry site during brain edema formation, and regulation of AQP4 may therefore be of therapeutic interest. Phosphorylation of aquaporins can regulate plasma membrane localization and, possibly, the unit water permeability via gating of the AQP channel itself. In vivo phosphorylation of six serine residues in the COOH terminus of AQP4 has been detected by mass spectrometry: Ser(276), Ser(285), Ser(315), Ser(316), Ser(321), and Ser(322). To address the role of these phosphorylation sites for AQP4 function, serine-to-alanine mutants were created to abolish the phosphorylation sites. All mutants were detected at the plasma membrane of transfected C6 cells, with the fraction of the total cellular AQP4 expressed at the plasma membrane of transfected C6 cells being similar between the wild-type (WT) and mutant forms of AQP4. Activation of protein kinases A, C, and G in primary astrocytic cultures did not affect the plasma membrane abundance of AQP4. The unit water permeability was determined for the mutant AQP4s upon heterologous expression in Xenopus laevis oocytes (along with serine-to-aspartate mutants of the same residues to mimic a phosphorylation). None of the mutant AQP4 constructs displayed alterations in the unit water permeability. Thus phosphorylation of six different serine residues in the COOH terminus of AQP4 appears not to be required for proper plasma membrane localization of AQP4 or to act as a molecular switch to gate the water channel.

Assentoft, Mette; Larsen, Brian R

2014-01-01

285

A new influenza virus virulence determinant: The NS1 protein four C-terminal residues modulate pathogenicity  

OpenAIRE

The virulence of influenza virus is a multigenic trait. One determinant of virulence is the multifunctional NS1 protein that functions in several ways to defeat the cellular innate immune response. Recent large-scale genome sequence analysis of avian influenza virus isolates indicated that four C-terminal residues of the NS1 protein is a PDZ ligand domain of the X-S/T-X-V type and it was speculated that it may represent a virulence determinant. To test this hypothesis, by using mice as a mode...

Jackson, David; Hossain, Md Jaber; Hickman, Danielle; Perez, Daniel R.; Lamb, Robert A.

2008-01-01

286

Effect of interferential current of different amplitude-modulated frequencies, on threshold and number of accommodations on healthy painless individuals / Efeito da corrente interferencial de diferentes frequências moduladas pela amplitude no limiar e número de acomodações em indivíduos saudáveis sem dor  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese JUSTIFICATIVA E OBJETIVOS: Apesar do uso generalizado da corrente interferencial, há controvérsias na literatura sobre os parâmetros ideais de estimulação utilizados. O objetivo deste estudo foi avaliar o limiar e o número total de acomodações em indivíduos estimulados por diferentes frequências mo [...] duladas pela amplitude. MÉTODOS: Trata-se de um ensaio clínico, cruzado, com amostra de conveniência aleatorizada e encoberta, composta por 20 indivíduos saudáveis, com idade média de 20,35 anos, de ambos os gêneros. Os voluntários foram submetidos a corrente interferencial por 20 minutos, na forma bipolar, com os eletrodos localizados na articulação do cotovelo, sendo posicionados um sobre a superficialidade do nervo ulnar e outro do nervo mediano. Os parâmetros do equipamento foram: frequência base de 4.000Hz, frequências moduladas pela amplitude de 1, 10 ou 100Hz (de acordo com o subgrupo do dia). Foi avaliado o limiar de acomodação e o número total de acomodações. RESULTADOS: Para o limiar de acomodação não foram encontradas diferenças significativas (p>0,05); quanto ao número de acomodações houve diferenças significativas entre as frequências de 10 e 100Hz (p Abstract in english BACKGROUND AND OBJECTIVES: Despite the widespread use of interferential current, controversy exists in the literature on the optimal stimulation parameters. The aim of this study was to evaluate the threshold and the total number of accommodations in subjects stimulated by different amplitude-modul [...] ated frequencies. METHODS: The study is a clinical, cross-over trial with randomized and blinded convenience sample consisted of 20 healthy subjects, with mean age of 20.35 years, of both genders. Volunteers underwent interferential current for 20 minutes, the bipolar form, with electrodes placed on the elbow joint being positioned one above the superficiality of the ulnar nerve and the other of the median nerve. Equipment parameters were: base frequency of 4,000Hz, amplitude-modulated frequencies 1, 10 or 100Hz (according to the subgroup). Threshold and total number of accommodations were assessed. RESULTS: For the accommodation threshold no significant differences were found (p>0.05). With regard to the number of accommodations, there have been significant differences between the frequencies of 10 and 100Hz (p

Beatriz Gavassa de, Araújo; Karina Maria, Filipin; Tathiane, Pasqualli; Lucinéia de Fátima Chasko, Ribeiro; Gladson Ricardo Flor, Bertolini.

2014-12-01

287

Subtle alteration of residues including N-linked glycans in V2 loop modulate HIV-1 neutralization by PG9 and PG16 monoclonal antibodies.  

Science.gov (United States)

Recent discovery of several potent and broadly neutralizing monoclonal antibodies (MAbs) (such as PG9 and PG16) to HIV-1 provided clues on newer vaccine targets. In the present study, we found an env clone obtained from a slow progressor showing significant resistance to PG9 and PG16 MAbs in sharp contrast to other contemporaneous autologous env clones. By constructing chimeric envelopes and specific substitutions we found that both loop length and spatial orientation of glycan residues in addition to the net charge of the ? sheet C region that directly binds to PG9 CDRH3 within V2 loop significantly modulated HIV-1 sensitivity to PG9 and PG16 MAbs. Similar observation were made with several other Envs which varied in length, glycan content and net charge in PG9 contacting complementary region in V2 loop. Our data indicated that subtle change within V2 loop alone modulates exposition of quaternary epitopes that are targets of PG9/PG16 MAbs. PMID:22314018

Ringe, Rajesh; Phogat, Sanjay; Bhattacharya, Jayanta

2012-04-25

288

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

289

Accurate Period Approximation for Any Simple Pendulum Amplitude  

International Nuclear Information System (INIS)

Accurate approximate analytical formulae of the pendulum period composed of a few elementary functions for any amplitude are constructed. Based on an approximation of the elliptic integral, two new logarithmic formulae for large amplitude close to 180° are obtained. Considering the trigonometric function modulation results from the dependence of relative error on the amplitude, we realize accurate approximation period expressions for any amplitude between 0 and 180°. A relative error less than 0.02% is achieved for any amplitude. This kind of modulation is also effective for other large-amplitude logarithmic approximation expressions. (fundamental areas of phenomenology(including applications))

290

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

291

Scattering Amplitudes in Gauge Theories  

CERN Document Server

This thesis is focused on the development of new mathematical methods for computing multi-loop scattering amplitudes in gauge theories. In this work we combine, for the first time, the unitarity-based construction for integrands, and the recently introduced integrand-reduction through multivariate polynomial division. After discussing the generic features of this novel reduction algorithm, we will apply it to the one- and two-loop five-point amplitudes in ${\\cal N}=4$ sYM. The integrands of the multiple-cuts are generated from products of tree-level amplitudes within the super-amplitudes formalism. The corresponding expressions will be used for the analytic reconstruction of the polynomial residues. Their parametric form is known a priori, as derived by means of successive polynomial divisions using the Gr\\"obner basis associated to the on-shell denominators. The integrand reduction method will be exploited to investigate the color-kinematic duality for multi-loop ${\\cal N}=4$ sYM scattering amplitudes. Our a...

Schubert, Ulrich

2014-01-01

292

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

International Nuclear Information System (INIS)

Purpose: To estimate the dosimetric impact of residual setup errors on parotid sparing in head-and-neck (H and N) intensity-modulated treatments and to evaluate the effect of employing an PRV (planning organ-at-risk volume) margin for the parotid gland. Patients and methods: Ten patients treated for H and N cancer were considered. A nine-beam intensity-modulated radiotherapy (IMRT) was planned for each patient. A second optimization was performed prescribing dose constraint to the PRV of the parotid gland. Systematic setup errors of 2 mm, 3 mm, and 5 mm were simulated. The dose-volume histograms of the shifted and reference plans were compared with regard to mean parotid gland dose (MPD), normal-tissue complication probability (NTCP), and coverage of the clinical target volume (V95% and equivalent uniform dose [EUD]); the sensitivity of parotid sparing on setup error was evaluated with a probability-based approach. Results: MPD increased by 3.4%/mm and 3.0%/mm for displacements in the craniocaudal and lateral direction and by 0.7%/mm for displacements in the anterior-posterior direction. The probability to irradiate the parotid with a mean dose > 30 Gy was > 50%, for setup errors in cranial and lateral direction and 95% and EUD variations < 1% and < 1 Gy). Conclusion: The parotid gland is more sensitive to craniocaudal and lateral displacements. A setup error of 2 mm guarantees an MPD ? 30 Gy in most cases, without adding a PRV margin. If greater displacements are expected/accepted, an adequate PRV margin could be used to meet the clinical parotid gland constraint of 30 Gy, without affecting target volume coverage. (orig.)

293

Vesícula residual Residual gallbladder  

Directory of Open Access Journals (Sweden)

Full Text Available Our objective is to report three patients with recurrent severe upper abdominal pain secondary to residual gallbladder. All patients had been subjected to cholecystectomy from 1 to 20 years before. The diagnosis was established after several episodes of severe upper abdominal pain by imaging exams: ultrasonography, tomography, or endoscopic retrograde cholangiography. Removal of the residual gallbladder led to complete resolution of symptoms. Partial removal of the gallbladder is a very rare cause of postcholecystectomy symptoms.

Júlio C. U. Coelho

2002-12-01

294

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

International Nuclear Information System (INIS)

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

295

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

Directory of Open Access Journals (Sweden)

Full Text Available Simultaneous measurements of the partial column-averaged dry air mixing ratio of CO2 (q and target range were demonstrated using airborne amplitude-modulated 1.57 ?m differential laser absorption spectrometry (LAS. The LAS system is useful for discriminating between ground and cloud return signals and has a demonstrated ability to suppress the impact of integrated aerosol signals on differential absorption optical depth (?? measurements. A high correlation coefficient (R of 0.99 between ?? observed by LAS and ?? calculated from in-situ measurements of CO2 was obtained. The averaged difference in q obtained from LAS (qLAS and validation data (qval was within 1.5 ppm for all spiral measurements. A significant profile was observed for both qLAS and qval, in which lower altitude CO2 decreases compared to higher altitude CO2 attributed to the photosynthesis over grassland in the summer. In the case of an urban area where CO2 and aerosol are highly distributed in the lower atmosphere in the winter, the difference of qLAS to qval is ?1.5 ppm, and evaluated qLAS is in agreement with qval within the measurement precision of 2.4 ppm (1?.

O. Uchino

2012-07-01

296

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

Science.gov (United States)

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

Zvorykin, V. D.; Ionin, Andrei A.; Levchenko, A. O.; Mesyats, Gennadii A.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, Igor V.; Sunchugasheva, E. S.; Ustinovskii, N. N.; Shutov, A. V.

2013-04-01

297

Histidine Residues in the Na+-coupled Ascorbic Acid Transporter-2 (SVCT2) Are Central Regulators of SVCT2 Function, Modulating pH Sensitivity, Transporter Kinetics, Na+ Cooperativity, Conformational Stability, and Subcellular Localization*  

Science.gov (United States)

Na+-coupled ascorbic acid transporter-2 (SVCT2) activity is impaired at acid pH, but little is known about the molecular determinants that define the transporter pH sensitivity. SVCT2 contains six histidine residues in its primary sequence, three of which are exofacial in the transporter secondary structure model. We used site-directed mutagenesis and treatment with diethylpyrocarbonate to identify histidine residues responsible for SVCT2 pH sensitivity. We conclude that five histidine residues, His109, His203, His206, His269, and His413, are central regulators of SVCT2 function, participating to different degrees in modulating pH sensitivity, transporter kinetics, Na+ cooperativity, conformational stability, and subcellular localization. Our results are compatible with a model in which (i) a single exofacial histidine residue, His413, localized in the exofacial loop IV that connects transmembrane helices VII-VIII defines the pH sensitivity of SVCT2 through a mechanism involving a marked attenuation of the activation by Na+ and loss of Na+ cooperativity, which leads to a decreased Vmax without altering the transport Km; (ii) exofacial histidine residues His203, His206, and His413 may be involved in maintaining a functional interaction between exofacial loops II and IV and influence the general folding of the transporter; (iii) histidines 203, 206, 269, and 413 affect the transporter kinetics by modulating the apparent transport Km; and (iv) histidine 109, localized at the center of transmembrane helix I, might be fundamental for the interaction of SVCT2 with the transported substrate ascorbic acid. Thus, histidine residues are central regulators of SVCT2 function. PMID:20843809

Ormazabal, Valeska; Zuñiga, Felipe A.; Escobar, Elizabeth; Aylwin, Carlos; Salas-Burgos, Alexis; Godoy, Alejandro; Reyes, Alejandro M.; Vera, Juan Carlos; Rivas, Coralia I.

2010-01-01

298

All-optical phase-preserving multilevel amplitude regeneration.  

Science.gov (United States)

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

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

2014-11-01

299

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

Science.gov (United States)

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

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

2013-05-01

300

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

OpenAIRE

A single nucleotide polymorphism (SNP) in codon 129 of the human prion gene, leading to a change from methionine to valine at residue 129 of prion protein (PrP), has been shown to be a determinant in the susceptibility to prion disease. However, the molecular basis of this effect remains unexplained. In the current study, we determined crystal structures of prion segments having either Met or Val at residue 129. These 6-residue segments of PrP centered on residue 129 are “steric zippers,”...

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

2010-01-01

301

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

Energy Technology Data Exchange (ETDEWEB)

A single nucleotide polymorphism (SNP) in codon 129 of the human prion gene, leading to a change from methionine to valine at residue 129 of prion protein (PrP), has been shown to be a determinant in the susceptibility to prion disease. However, the molecular basis of this effect remains unexplained. In the current study, we determined crystal structures of prion segments having either Met or Val at residue 129. These 6-residue segments of PrP centered on residue 129 are 'steric zippers,' pairs of interacting {beta}-sheets. Both structures of these 'homozygous steric zippers' reveal direct intermolecular interactions between Met or Val in one sheet and the identical residue in the mating sheet. These two structures, plus a structure-based model of the heterozygous Met-Val steric zipper, suggest an explanation for the previously observed effects of this locus on prion disease susceptibility and progression.

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

2010-09-23

302

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

303

Connection between the period and the amplitude of the Blazhko effect  

OpenAIRE

We found a possible relationship between the modulation period and the amplitude of the Blazhko RR Lyrae stars: long modulation period generally implies high modulation amplitude while the short modulation period results in small amplitude. Although this effect is much more a tendency than a strict rule, it can be detected easily in the space-born time series data produced by Kepler and CoRoT. Good quality ground-based data show this relation, too. This phenomenon could give...

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

2014-01-01

304

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

305

Calcium modulation of 5-HT3 receptor binding and function  

OpenAIRE

Calcium modulates the 5-HT3 receptor response by reducing peak current amplitude and increasing rates of activation, deactivation and desensitisation, but the binding site(s) and mechanism(s) of this modulation are unknown. Here we study residues that may be involved in calcium binding in two partially overlapping regions of the extracellular domain (E213-E215-E218 and D204-E218-V219). The modulatory effects of calcium were assessed by radioligand binding and whole-cell patch-clamp. Compariso...

Thompson, Andrew J.; Lummis, Sarah C. R.

2009-01-01

306

Finite amplitude envelope solitons  

International Nuclear Information System (INIS)

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

307

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

308

Identification of residues involved in the interaction of Staphylococcus aureus fibronectin-binding protein with the (4)F1(5)F1 module pair of human fibronectin using heteronuclear NMR spectroscopy.  

OpenAIRE

Many pathogenic Gram-positive bacteria express cell surface proteins that bind to components of the extracellular matrix. This paper describes studies of the interaction between ligand binding repeats (D3 and D1-D4) of a fibronectin-binding protein from Staphylococcus aureus with a module pair ((4)F1(5)F1) from the N-terminal region of fibronectin. When D3 was added to isotope-labeled (4)F1(5)F1, (1)H, (15)N, and (13)C NMR chemical shift changes indicate that binding is primarily via residues...

Penkett, Cj; Dobson, Cm; Smith, Lj; Bright, Jr; Pickford, Ar; Campbell, Id; Potts, Jr

2000-01-01

309

Modified ? ? amplitude with ? pole  

Science.gov (United States)

A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (? ? , K K ¯, and ? ? ) and P (? ? , ? 2 ? , and ? ? ) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the ? ? threshold region. Moreover, the pole of the S wave amplitude related with the f0(500 ) meson (former f0(600 ) or ? ) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the ? pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, ? ? amplitudes with a heavy and broad ? meson without changing of their original mathematical structure.

Bydžovský, P.; Kami?ski, R.; Nazari, V.

2014-12-01

310

Residuation theory  

CERN Document Server

Residuation Theory aims to contribute to literature in the field of ordered algebraic structures, especially on the subject of residual mappings. The book is divided into three chapters. Chapter 1 focuses on ordered sets; directed sets; semilattices; lattices; and complete lattices. Chapter 2 tackles Baer rings; Baer semigroups; Foulis semigroups; residual mappings; the notion of involution; and Boolean algebras. Chapter 3 covers residuated groupoids and semigroups; group homomorphic and isotone homomorphic Boolean images of ordered semigroups; Dubreil-Jacotin and Brouwer semigroups; and loli

Blyth, T S; Sneddon, I N; Stark, M

2014-01-01

311

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

OpenAIRE

Voltage-gated channel proteins sense a change in the transmembrane electric field and respond with a conformational change that allows ions to diffuse across the pore-forming structure. Site-specific mutagenesis combined with electrophysiological analysis of expressed mutants in amphibian oocytes has previously established the S4 transmembrane segment as an element of the voltage sensor. Here, we show that mutations of conserved negatively charged residues in S2 and S3 of a brain K+ channel, ...

Planells-cases, R.; Ferrer-montiel, A. V.; Patten, C. D.; Montal, M.

1995-01-01

312

Residual stresses  

International Nuclear Information System (INIS)

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

313

High amplitude propagated contractions.  

Science.gov (United States)

While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. High amplitude propagated contractions occur spontaneously, in response to pharmacological agents or colonic distention. A subset of patients with slow transit constipation have fewer HAPC. In this issue of Neurogastroenterology and Motility, Rodriguez et al. report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in constipated children undergoing colonic manometry. Moreover, and consistent with a neural mechanism, anal relaxation often precedes arrival of HAPC in the left colon. High amplitude propagated contractions are also used to evaluate the motor response to a meal and pharmacological stimuli (e.g., bisacodyl, neostigmine) and to identify colonic inertia during colonic motility testing in chronic constipation. This editorial comprehensively reviews the characteristics, physiology and pharmacology of HAPC, their assessment by manometry, and relevance to constipation and diarrhea. PMID:23057554

Bharucha, A E

2012-11-01

314

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  

OpenAIRE

The detection of small-amplitude nonradial modes in high-amplitude Delta Sct (HADS) variables has been very elusive until at least five of them were detected in the light curve of V974 Oph obtained from ground-based observations. The combination of radial and nonradial modes has a high asteroseismic potential, thanks to the strong constraints we can put in the modelling. The continuous monitoring of ASAS 192647-0030.0=CoRoT 101155310 (P=0.1258 d, V=13.4) ensured from space b...

Poretti, Ennio; Rainer, Monica; 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

315

Amplitude interference and interferometry  

International Nuclear Information System (INIS)

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

316

Covariant Multiloop Superstring Amplitudes  

CERN Document Server

In these proceedings, the multiloop amplitude prescription using the super-Poincare invariant pure spinor formalism for the superstring is reviewed. Unlike the RNS prescription, there is no sum over spin structures and surface terms coming from the boundary of moduli space can be ignored. Massless N-point multiloop amplitudes vanish for N<4, which implies (with two mild assumptions) the perturbative finiteness of superstring theory. And R^4 terms receive no multiloop corrections in agreement with the Type IIB S-duality conjecture of Green and Gutperle.

Berkovits, N

2004-01-01

317

Improved cardiac phase/amplitude functional imaging  

International Nuclear Information System (INIS)

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

318

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

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

Dimsdle, Jeffrey William (Overland Park, KS)

2007-07-03

319

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

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

Dimsdle, Jeffrey William (Overland Park, KS)

2007-07-17

320

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

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

Dimsdle, Jeffrey William (Overland Park, KS)

2009-09-01

321

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

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

Dimsdle, Jeffrey William (Overland Park, KS)

2007-10-02

322

Method of differential-phase/absolute-amplitude QAM  

Energy Technology Data Exchange (ETDEWEB)

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

Dimsdle, Jeffrey William (Overland Park, KS)

2008-10-21

323

Reinforcing Saccadic Amplitude Variability  

Science.gov (United States)

Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…

Paeye, Celine; Madelain, Laurent

2011-01-01

324

Higher Order Cummulants based Digital Modulation Recognition Scheme  

OpenAIRE

In this study, we have presented that Higher Order Cummulants (HOC) based modulation recognition scheme for Pulse Amplitude Modulation (PAM), Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK) modulated signals having orders of 2 to 64. Modulation recognition is a process to recognize the signal modulation type which is received by the receiver in the presence of channel noise. The HOC based MR is accomplished in two modules. First is feature extraction using higher order cumm...

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

2013-01-01

325

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

326

Cavity enhanced terahertz modulation  

International Nuclear Information System (INIS)

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

327

Adaptive Modulation (QPSK, QAM)  

OpenAIRE

In this paper, introduced below are the concepts of digital modulation used in many communication systems today. Techniques described include quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) and how these techniques can be used to increase the capacity and speed of a wireless network. These modulation techniques are the basis of communications for systems like cable modems, DSL modems, CDMA, 3G, Wi-Fi* (IEEE 802.11) and WiMAX* (IEEE 802.16).

Masood, Rao Farhat

2013-01-01

328

Universal boundary reflection amplitudes  

International Nuclear Information System (INIS)

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

329

Renormalization of Massless Feynman Amplitudes in Configuration Space  

CERN Document Server

A systematic study of recursive renormalization of Feynman amplitudes is carried out both in Euclidean and in Minkowski configuration space. For a massless quantum field theory (QFT) we use the technique of extending associate homogeneous distributions to complete the renormalization recursion. A homogeneous (Poincare covariant) amplitude is said to be convergent if it admits a (unique covariant) extension as a homogeneous distribution. For any amplitude without subdivergences - i.e. for a Feynman distribution that is homogeneous off the full (small) diagonal - we define a renormalization invariant residue. Its vanishing is a necessary and sufficient condition for the convergence of such an amplitude. It extends to arbitrary - not necessarily primitively divergent - Feynman amplitudes. This notion of convergence is finer than the usual power counting criterion and includes cancellation of divergences.

Nikolov, Nikolay M

2013-01-01

330

Fatigue crack growth under variable amplitude loading  

Science.gov (United States)

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

Sidawi, Jihad A.

1994-09-01

331

Connection between the period and the amplitude of the Blazhko effect  

CERN Document Server

We found a possible relationship between the modulation period and the amplitude of the Blazhko RR Lyrae stars: long modulation period generally implies high modulation amplitude while the short modulation period results in small amplitude. Although this effect is much more a tendency than a strict rule, it can be detected easily in the space-born time series data produced by Kepler and CoRoT. Good quality ground-based data show this relation, too. This phenomenon could give us constraints for the physics of the Blazhko effect.

Benk?, J M

2014-01-01

332

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

333

Bekki-Nozaki Amplitude Holes in Hydrothermal Nonlinear Waves  

Science.gov (United States)

We present and analyze experimental results on the dynamics of hydrothermal waves occurring in a laterally heated fluid layer. We argue that the large-scale modulations of the waves are governed by a one-dimensional complex Ginzburg-Landau equation (CGLE). We determine quantitatively all the coefficients of this amplitude equation using the localized amplitude holes observed in the experiment, which we show to be well described as Bekki-Nozaki hole solutions of the CGLE.

Burguete, Javier; Chaté, Hugues; Daviaud, François; Mukolobwiez, Nathalie

1999-04-01

334

Scaling movement amplitude: adaptation of timing and amplitude control in a bimanual task.  

Science.gov (United States)

Participants traced two circles simultaneously and the diameter of one circle was scaled as the diameter of the other circle remained constant. When the scaled circle was larger, amplitude error shifted from overshooting to undershooting, while shifting from undershooting to overshooting when this circle was smaller. Asymmetric coordination was unstable when the left arm traced a circle larger than the right arm, yet stable when the left arm traced a smaller circle. When producing symmetric coordination and the left arm traced the larger circle, relative phase shifted by 30°, but a right arm lead predominated. When the left arm traced the smaller circle and symmetric coordination was required, a 30° shift in relative phase occurred, but hand lead changed from left to right. The modulation of movement amplitude and relative phase emerged simultaneously as a result of neural crosstalk effects linked to initial amplitude conditions and possibly visual feedback of the hands' motion. PMID:22420780

Buchanan, John J; Ryu, Young U

2012-01-01

335

Amplitude equations for stochastic partial differential equations  

CERN Document Server

Rigorous error estimates for amplitude equations are well known for deterministic PDEs, and there is a large body of literature over the past two decades. However, there seems to be a lack of literature for stochastic equations, although the theory is being successfully used in the applied community, such as for convective instabilities, without reliable error estimates at hand. This book is the first step in closing this gap. The author provides details about the reduction of dynamics to more simpler equations via amplitude or modulation equations, which relies on the natural separation of time-scales present near a change of stability. For students, the book provides a lucid introduction to the subject highlighting the new tools necessary for stochastic equations, while serving as an excellent guide to recent research.

Blömker, Dirk

2007-01-01

336

Direct modulation of 56 Gbps duobinary-4-PAM  

DEFF Research Database (Denmark)

This paper reports on the direct modulation of externally modulated laser and transmission through single mode fiber of a 56 Gbps duobinary-4-pulse amplitude modulation signal through 10 GHz class optics.

Suhr, Lau Frejstrup; Vegas Olmos, Juan José

337

High Frequency Amplitude Detector for GMI Magnetic Sensors  

Directory of Open Access Journals (Sweden)

Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

Aktham Asfour

2014-12-01

338

Residual basins  

International Nuclear Information System (INIS)

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

339

Full one-loop amplitudes from tree amplitudes  

OpenAIRE

We establish an efficient polynomial-complexity algorithm for one-loop calculations, based on generalized $D$-dimensional unitarity. It allows automated computations of both cut-constructible {\\it and} rational parts of one-loop scattering amplitudes from on-shell tree amplitudes. We illustrate the method by (re)-computing all four-, five- and six-gluon scattering amplitudes in QCD at one-loop.

Giele, Walter T.; Kunszt, Zoltan; Melnikov, Kirill

2008-01-01

340

Scattering amplitudes from multivariate polynomial division  

Energy Technology Data Exchange (ETDEWEB)

We show that the evaluation of scattering amplitudes can be formulated as a problem of multivariate polynomial division, with the components of the integration-momenta as indeterminates. We present a recurrence relation which, independently of the number of loops, leads to the multi-particle pole decomposition of the integrands of the scattering amplitudes. The recursive algorithm is based on the weak Nullstellensatz theorem and on the division modulo the Groebner basis associated to all possible multi-particle cuts. We apply it to dimensionally regulated one-loop amplitudes, recovering the well-known integrand-decomposition formula. Finally, we focus on the maximum-cut, defined as a system of on-shell conditions constraining the components of all the integration-momenta. By means of the Finiteness Theorem and of the Shape Lemma, we prove that the residue at the maximum-cut is parametrized by a number of coefficients equal to the number of solutions of the cut itself.

Mastrolia, Pierpaolo, E-mail: pierpaolo.mastrolia@cern.ch [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Muenchen (Germany); Dipartimento di Fisica e Astronomia, Universita di Padova, Padova (Italy); INFN Sezione di Padova, via Marzolo 8, 35131 Padova (Italy); Mirabella, Edoardo, E-mail: mirabell@mppmu.mpg.de [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Muenchen (Germany); Ossola, Giovanni, E-mail: GOssola@citytech.cuny.edu [New York City College of Technology, City University of New York, 300 Jay Street, Brooklyn, NY 11201 (United States); Graduate School and University Center, City University of New York, 365 Fifth Avenue, New York, NY 10016 (United States); Peraro, Tiziano, E-mail: peraro@mppmu.mpg.de [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Muenchen (Germany)

2012-11-15

341

Scattering amplitudes from multivariate polynomial division  

International Nuclear Information System (INIS)

We show that the evaluation of scattering amplitudes can be formulated as a problem of multivariate polynomial division, with the components of the integration-momenta as indeterminates. We present a recurrence relation which, independently of the number of loops, leads to the multi-particle pole decomposition of the integrands of the scattering amplitudes. The recursive algorithm is based on the weak Nullstellensatz theorem and on the division modulo the Gröbner basis associated to all possible multi-particle cuts. We apply it to dimensionally regulated one-loop amplitudes, recovering the well-known integrand-decomposition formula. Finally, we focus on the maximum-cut, defined as a system of on-shell conditions constraining the components of all the integration-momenta. By means of the Finiteness Theorem and of the Shape Lemma, we prove that the residue at the maximum-cut is parametrized by a number of coefficients equal to the number of solutions of the cut itself.

342

Dissolving N = 4 loop amplitudes into QCD tree amplitudes.  

Science.gov (United States)

We use the infrared consistency of one-loop amplitudes in N = 4 Yang-Mills theory to derive a compact analytic formula for a tree-level next-to-next-to-maximal helicity-violating gluon scattering amplitude in QCD, the first such formula known. We argue that the infrared conditions, coupled with recent advances in calculating one-loop box coefficients, can give a new tool for computing tree-level amplitudes in general. Our calculation suggests that many amplitudes have a structure which is even simpler than that revealed so far by current twistor-space constructions. PMID:15783477

Roiban, Radu; Spradlin, Marcus; Volovich, Anastasia

2005-03-18

343

Dissolving N=4 loop amplitudes into QCD tree amplitudes  

International Nuclear Information System (INIS)

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

344

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

Science.gov (United States)

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

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

2014-12-01

345

The pulsed amplitude unit for the SLC  

Energy Technology Data Exchange (ETDEWEB)

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

Rolfe, J.; Browne, M.J.; Jobe, R.K.

1987-02-01

346

The pulsed amplitude unit for the SLC  

International Nuclear Information System (INIS)

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

347

Amplitude analysis of hadron decays  

CERN Document Server

We provide succinct covariant amplitude decompositions of 2-body weak hadronic decays, with which to compare data, including exclusive rates, helicity amplitudes and polarizations. For weak decays, the systematic dependence of these amplitudes on masses and quantum numbers of participating particles are determined within a factor of about two by the CKM angles and the Fermi constant so theoretical models need to be much more accurate if they are to be convincing.

Delbourgo, Robert; Liu, Dongsheng

1998-01-01

348

Hidden beauty in multiloop amplitudes  

International Nuclear Information System (INIS)

Planar L-loop maximally helicity violating amplitudes in N = 4 supersymmetric Yang-Mills theory are believed to possess the remarkable property of satisfying iteration relations in L. We propose a simple new method for studying iteration relations for four-particle amplitudes which involves the use of certain linear differential operators and eliminates the need to fully evaluate any loop integrals. We carry out this procedure in explicit detail for the two-loop amplitude and prove that this method can be applied to any multiloop integral, allowing a conjectured iteration relation for any given amplitude to be tested up to polynomials in logarithms

349

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

350

Graviton Amplitudes from Collinear Limits of Gauge Amplitudes  

CERN Document Server

We express all tree-level graviton amplitudes in Einstein's gravity as the collinear limits of a linear combination of pure Yang-Mills amplitudes in which each graviton is represented by two gauge bosons, each of them carrying exactly one half of graviton's momentum and helicity.

Stieberger, Stephan

2015-01-01

351

47 CFR 73.758 - System specifications for digitally modulated emissions in the HF broadcasting service.  

Science.gov (United States)

...lower bounds noted in this paragraph. (4) Modulation. Quadrature amplitude modulation (QAM) with orthogonal frequency division multiplexing (OFDM) shall be used. 64-QAM is feasible under many propagation...

2010-10-01

352

Cross-Channel Amplitude Sweeps Are Crucial to Speech Intelligibility  

Science.gov (United States)

Classical views of speech perception argue that the static and dynamic characteristics of spectral energy peaks (formants) are the acoustic features that underpin phoneme recognition. Here we use representations where the amplitude modulations of sub-band filtered speech are described, precisely, in terms of co-sinusoidal pulses. These pulses are…

Prendergast, Garreth; Green, Gary G. R.

2012-01-01

353

Five-particle one-loop closed string amplitudes and supersymmetry relations  

Science.gov (United States)

The explicit covariant forms for the three-boson-two-fermion and the one-boson-four-fermion scattering amplitudes at one-loop level in closed superstring theory are presented. The amplitudes are shown to have the correct factorization properties at kinematic poles, yielding as residues of these poles the well-known four-particle amplitudes. The analysis shows, for the first time at the one-loop level, a verification of the supersymmetry properties of the vertices.

Lin, Zhong-heng; Jones, S. T.

1989-01-01

354

Five-particle one-loop closed string amplitudes and supersymmetry relations  

Energy Technology Data Exchange (ETDEWEB)

The explicit covariant forms for the three-boson-two-fermion and the one-boson-four-fermion scattering amplitudes at one-loop level in closed superstring theory are presented. The amplitudes are shown to have the correct factorization properties at kinematic poles, yielding as residues of these poles the well-known four-particle amplitudes. The analysis shows, for the first time at the one-loop level, a verification of the supersymmetry properties of the vertices.

Lin Zhongheng; Jones, S.T.

1989-01-19

355

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

OpenAIRE

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

Mahmud, Mohammad; Naydenova, Izabela; Toal, Vincent

2008-01-01

356

Encouraging Early Clinical Outcomes With Helical Tomotherapy–Based Image-Guided Intensity-Modulated Radiation Therapy for Residual, Recurrent, and/or Progressive Benign/Low-Grade Intracranial Tumors: A Comprehensive Evaluation  

International Nuclear Information System (INIS)

Purpose: To report early clinical outcomes of helical tomotherapy (HT)-based image-guided intensity-modulated radiation therapy (IMRT) in brain tumors of varying shape, size, and location. Materials and Methods: Patients with residual, recurrent, and/or progressive low-grade intracranial and skull-base tumors were treated on a prospective protocol of HT-based IMRT and followed clinicoradiologically. Standardized metrics were used for plan evaluation and outcome analysis. Results: Twenty-seven patients with 30 lesions were treated to a median radiotherapy dose of 54 Gy in 30 fractions. All HT plans resulted in excellent target volume coverage with steep dose-gradients. The mean (standard deviation) dose homogeneity index and conformity index was 0.07 (0.05) and 0.71 (0.08) respectively. At first response assessment, 20 of 30 lesions were stable, whereas 9 showed partial regression. One patient with a recurrent clival chordoma though neurologically stable showed imaging-defined progression, whereas another patient with stable disease on serial imaging had sustained neurologic worsening. With a median follow-up of 19 months (interquartile range, 11–26 months), the 2-year clinicoradiological progression-free survival and overall survival was 93.3% and 100% respectively. Conclusions: Careful selection of radiotherapy technique is warranted for benign/low-grade brain tumors to achieve durable local control with minimum long-term morbidity. Large or complex-shaped tumors bbidity. Large or complex-shaped tumors benefit most from IMRT. Our early clinical experience of HT-based IMRT for brain tumors has been encouraging.

357

CESR feedback system using a constant amplitude pulser  

International Nuclear Information System (INIS)

Particle beam feedback system using constant-amplitude, 1000 V, 12 ns pulses has been built to provide longitudinal and horizontal feedback for stabilizing 14 ns spaced bunches for use in CESR (Cornell Electron Storage Ring). The pulse rate is modulated to obtain proportional amplitude control and the pulse arrival time is modulated to obtain both positive and negative kicks. The average repetition rate is limited by pulser power dissipation, but the instantaneous rate may be increased to full duty cycle for short periods of time to handle transients. The pulser drives a 50-ohm stripline kicker so the equivalent peak power at 1000 V is 10 kW. The characteristics of the pulser and its modulator will be described along with the system's operation

358

Double-Cut of Scattering Amplitudes and Stokes' Theorem  

CERN Document Server

We show how Stokes' Theorem, in the fashion of the Generalised Cauchy Formula, can be applied for computing double-cut integrals of one-loop amplitudes analytically. It implies the evaluation of phase-space integrals of rational functions in two complex-conjugated variables, which are simply computed by an indefinite integration in a single variable, followed by Cauchy's Residue integration in the conjugated one. The method is suitable for the cut-construction of the coefficients of 2-point functions entering the decomposition of one-loop amplitudes in terms of scalar master integrals.

Mastrolia, Pierpaolo

2009-01-01

359

Cross-Modulation Interference with Lateralization of Mixed-Modulated Waveforms  

Science.gov (United States)

Purpose: This study investigated the ability to use spatial information in mixed-modulated (MM) sounds containing concurrent frequency-modulated (FM) and amplitude-modulated (AM) sounds by exploring patterns of interference when different modulation types originated from different loci as may occur in a multisource acoustic field. Method:…

Hsieh, I-Hui; Petrosyan, Agavni; Goncalves, Oscar F.; Hickok, Gregory; Saberi, Kourosh

2010-01-01

360

Unitarized pion-nucleon scattering amplitude from inverse amplitude method  

CERN Document Server

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

Porto-Cavalcante, I; Cavalcante, Isabela P.

2003-01-01

361

Scattering amplitudes in Lifshitz spacetime  

OpenAIRE

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 th...

Andrade, Tomas; Lei, Yang; Ross, Simon F.

2014-01-01

362

Small-amplitude defocusing nematicons  

Science.gov (United States)

Using a perturbation theory based on multiple scales analysis we obtain small amplitude nematicon structures in the defocusing (normal dispersion) regime. The nonlocal equations that describe light propagation through a liquid crystal are reduced to a Korteweg–de Vries (KdV) equation. As such, it is found that under certain conditions there exist dark and anti-dark (small amplitude) nematicons; the criterion is the sign of a constant quantity that relates to the physical parameters of the system. The amplitudes, velocities and phases of these pulses are obtained in closed form and are closely related to the soliton solution of the related KdV equation.

Horikis, Theodoros P.

2015-01-01

363

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

364

Scattering amplitudes in gauge theories  

CERN Document Server

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

365

Positive Amplitudes In The Amplituhedron  

CERN Document Server

The all-loop integrand for scattering amplitudes in planar N = 4 SYM is determined by an "amplitude form" with logarithmic singularities on the boundary of the amplituhedron. In this note we provide strong evidence for a new striking property of the superamplitude, which we conjecture to be true to all loop orders: the amplitude form is positive when evaluated inside the amplituhedron. The statement is sensibly formulated thanks to the natural "bosonization" of the superamplitude associated with the amplituhedron geometry. However this positivity is not manifest in any of the current approaches to scattering amplitudes, and in particular not in the cellulations of the amplituhedron related to on-shell diagrams and the positive grassmannian. The surprising positivity of the form suggests the existence of a "dual amplituhedron" formulation where this feature would be made obvious. We also suggest that the positivity is associated with an extended picture of amplituhedron geometry, with the amplituhedron sitting...

Arkani-Hamed, Nima; Trnka, Jaroslav

2014-01-01

366

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

367

Pion photoproduction and ?N ? ? amplitudes  

International Nuclear Information System (INIS)

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

368

Mapping Pn amplitude spreading and attenuation in Asia  

Energy Technology Data Exchange (ETDEWEB)

Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.

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

2010-12-06

369

N = 4 scattering amplitudes and the deformed Graßmannian  

Science.gov (United States)

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

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

2014-12-01

370

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

371

Motivic Amplitudes and Cluster Coordinates  

CERN Document Server

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

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

2013-01-01

372

Variable amplitude fatigue crack growth behavior - a short overview  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-03-15

373

Variable amplitude fatigue crack growth behavior - a short overview  

International Nuclear Information System (INIS)

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

374

Large-amplitude Love waves  

CERN Document Server

In the context of the finite elasticity theory, we consider a model for compressible solids called 'compressible neo-Hookean material'. We show how finite-amplitude inhomogeneous plane wave solutions and finite-amplitude unattenuated solutions can combine to form a finite-amplitude Love wave. We take a layer of finite thickness overlying a solid half-space, both made of different prestressed compressible neo-Hookean materials. We derive an exact solution of the equations of motion and boundary conditions and also obtain results for the energy density and the energy flux of the waves. Finally, we investigate the special case when the interface between the layer and the substrate is in a principal plane of the prestrain. A numerical example is given.

Ferreira, Elizabete Rodrigues; Destrade, Michel; 10.1093/qjmam/hbn013

2008-01-01

375

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

376

Large amplitude oscillatory elongation flow  

DEFF Research Database (Denmark)

A filament stretching rheometer (FSR) was used for measuring the elongation flow with a large amplitude oscillative elongation imposed upon the flow. The large amplitude oscillation imposed upon the elongational flow as a function of the time t was defined as epsilon(t) =(epsilon) over dot(0)t + Lambda[1 - cos( 2 pi Omega(epsilon) over dot(0)t)] where epsilon is the Hencky strain, (epsilon) over dot(0) is a constant elongational rate for the base elongational flow, Lambda the strain amplitude ( Lambda >= 0), and Omega the strain frequency. A narrow molecular mass distribution linear polystyrene with a molecular weight of 145 kg/ mol was subjected to the oscillative flow. The onset of the steady periodic regime is reached at the same Hencky strain as the onset of the steady elongational viscosity ( Lambda = 0). The integral molecular stress function formulation within the 'interchain pressure' concept agrees qualitatively with the experiments.

Rasmussen, Henrik K.; Laillé, Philippe

2008-01-01

377

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

International Nuclear Information System (INIS)

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

378

Thin Photoresponding Elements with Frequency and Amplitude Modulations  

OpenAIRE

Nanoscale templated metal oxide thin films undoubtedly appertain to the most extensively studied materials due to their optical and electrochemical properties. Their photo-induced properties arise from the semiconductor nature, especially from the ability of the light quantum absorption followed by the charge carrier generation. In order to produce metal oxide thin layer layers, the liquid sol containing also the templating bodies, and confining nanoparticles, must be coated onto a substrat...

Kluson?, Petr

2013-01-01

379

Wave instability under short-wave amplitude modulations  

International Nuclear Information System (INIS)

The instabilities of nonlinear waves with a square-root dispersion ???(|k|) are studied. We present a new type of instability that affects wavelengths of the order of the carrier wave. This instability can initiate the formation of collapses and of narrow pulses.

380

Wave instability under short-wave amplitude modulations  

Science.gov (United States)

The instabilities of nonlinear waves with a square-root dispersion ???{|k|} are studied. We present a new type of instability that affects wavelengths of the order of the carrier wave. This instability can initiate the formation of collapses and of narrow pulses.

Rumpf, Benno; Newell, Alan C.

2013-08-01

381

Intermittency in amplitude modulated dynamic atomic force microscopy  

International Nuclear Information System (INIS)

From a mathematical point of view, the atomic force microscope (AFM) belongs to a special class of continuous time dynamical systems with intermittent impact collisions. Discontinuities of the velocity result from the collisions of the tip with the surface. Transition to chaos in non-linear systems can occur via the following four routes: bifurcation cascade, crisis, quasi-periodicity, and intermittency. For the AFM period doubling and period-adding cascades are well established. Other routes into chaos, however, also may play an important role. Time series data of a dynamic AFM experiment indicates a chaotic mode that is related to the intermittency route into chaos. The observed intermittency is characterized as a type III intermittency. Understanding the dynamics of the system will help improve the overall system performance by keeping the operation parameters of dynamic AFM in a range, where chaos can be avoided or at least controlled.

382

Research of informative efficiency of amplitude modulation of many components  

OpenAIRE

?????????? ???????????? ???????????? ?????? ????????? ????????? ??????? – ??????????? ????????? ???????? ????????? (????). ????????? ???????????? ?????? ???????????? ???? ?? ???????????? ??????????? ????????? (???). ?? ?????? ?????????? ??????? ????????? ??????????...

?????????, ?. ?.

2010-01-01

383

Power Module  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: In this paper, we discuss the upgrade problem of module, and introduce the concepts of the power module, regular power module and uniform power module. We give some results of them? Key words: power group; power module; regular power module; uniform power module

Gang Fang

2009-06-01

384

Power Module  

OpenAIRE

Abstract: In this paper, we discuss the upgrade problem of module, and introduce the concepts of the power module, regular power module and uniform power module. We give some results of them? Key words: power group; power module; regular power module; uniform power module

Gang Fang

2009-01-01

385

Observing rapid quasi-wave ionospheric disturbance using amplitude charts  

Science.gov (United States)

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

Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey

386

Phase and amplitude characteristics of InP:Fe modified interdigitated gap photoconductive microwave switches  

Science.gov (United States)

The transmission amplitude and phase characteristics of InP:Fe modified interdigitated gap photoconductive microwave switches are reported. Measurements in the 0.1-1 GHz frequency range show that the phase is shifted about 90 deg and that the corresponding change in amplitude ranges from 43 dB at 0.1 GHz to 23 dB at 1 GHz when the illumination-induced conductance is switched from a low OFF-state value (aboit 4 x 10 to the -8 S) to a high ON-state value (5 mS). The observed characteristics can be described by a phase-shifting region and an amplitude modulation region. In the phase-shifting region the phase strongly depends on the conductance, and the amplitude is almost constant. In the amplitude modulation region both the amplitude and the phase depend on the conductance but the effect on the amplitude is much more pronounced. A lumped-element model describing the device performance is presented. It is concluded that these optoelectronic microwave switching devices are suitable for high-speed amplitude modulation but are not promising as high-speed phase shifters.

Andersson, Ingmar L.; Eng, Sverre T.

1989-01-01

387

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

388

Master equations for master amplitudes  

International Nuclear Information System (INIS)

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

389

Master Equations for Master Amplitudes  

OpenAIRE

The general lines of the derivation and the main properties of the master equations for the master amplitudes associated to a given Feynman graph are recalled. Some results for the 2-loop self-mass graph with 4 propagators are then presented.

Caffo, M.; Czyz, H.; Laporta, S.; Remiddi, E.

1998-01-01

390

K anti K amplitude analyses  

International Nuclear Information System (INIS)

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

391

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.

392

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

393

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.)

394

Twisted Amplitude Phase Shift Keying  

Science.gov (United States)

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

2013-03-01

395

Amplitude analysis for D ? K? decays  

International Nuclear Information System (INIS)

An amplitude analysis for D ? K? decay is made. The ratio of the two isospin amplitudes I=1/2 and 2/3 is calculated. The relative phase of these two amplitudes is determined. A re-analysis of K?2? decay amplitude is also presented. (author)

396

Natural Generalization of Bosonic String Amplitudes  

OpenAIRE

The similarity between tree-level string theory scalar amplitudes, the Koba-Nielsen form ($S^{1}$) and the Virasoro-Shapiro form ($S^{2}$) suggests a natural $S^{n}$ generalization for a scalar amplitude. It is shown that the $S^{n}$ amplitude shares many essential properties of the string theory amplitudes, including $SO(n+1,1)$ conformal symmetry and linear Regge trajectories for the mass spectrum. We also discuss factorization and the critical dimension for the amplitude,...

Natsuume, Makoto

1993-01-01

397

Periodic instantons and scattering amplitudes  

International Nuclear Information System (INIS)

We discuss the role of periodic euclidean solutions with two turning points and zero winding number (periodic instantons) in instanton induced processes below the sphaleron energy Esph. We find that the periodic instantons describe certain multiparticle scattering events leading to the transitions between topologically distinct vacua. Both the semiclassical amplitudes and inital and final states of these transitions are determined by the periodic instantons. Furthermore, the corresponding probabilities are maximal among all states of given energy. We show that at E ? Esph, the periodic instantons can be approximated by infinite chains of ordinary instantons and anti-instantons, and they naturally emerge as deformations of the zero energy instanton. In the framework of 2d abelian Higgs model and 4d electroweak theory we show, however, that there is not obvious relation between periodic instantons and two-particle scattering amplitudes. (orig.)

398

Amplitude dropout in coupled lasers  

International Nuclear Information System (INIS)

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

399

Nonperturbative Calculation of Scattering Amplitudes  

OpenAIRE

A method for the nonperturbative calculation of scattering amplitudes and cross sections is discussed in the context of light-cone quantization. The Lanczos-based recursion method of Haydock is suggested for the computation of matrix elements of the resolvent for the light-cone Hamiltonian, from which the T-matrix can be constructed. The scattering of composite particles is handled by a generalization of a formulation given by Wick.

Hiller, J. R.

2000-01-01

400

Positivity of Spin Foam Amplitudes  

CERN Document Server

The amplitude for a spin foam in the Barrett-Crane model of Riemannian quantum gravity is given as a product over its vertices, edges and faces, with one factor of the Riemannian 10j symbols appearing for each vertex, and simpler factors for the edges and faces. We prove that these amplitudes are always nonnegative for closed spin foams. This means one can use the Metropolis algorithm to compute expectation values of observables in the Riemannian Barrett--Crane model, as in statistical mechanics, even though this theory is based on a real-time (exp(iS)) rather than imaginary-time (exp(-S)) path integral. Our proof uses the fact that when the Riemannian 10j symbols are nonzero, their sign is positive or negative depending on whether the sum of the ten spins is an integer or half-integer. For the product of 10j symbols appearing in the amplitude for a closed spin foam, these signs cancel. We conclude with some numerical evidence suggesting that the Lorentzian 10j symbols are also nonnegative.

Baez, J C; Baez, John C.

2002-01-01

401

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,

402

Residuated Basic Logic I  

OpenAIRE

We study the residuated basic logic ($\\mathsf{RBL}$) of residuated basic algebra in which the basic implication of Visser's basic propositional logic ($\\mathsf{BPL}$) is interpreted as the right residual of a non-associative binary operator $\\cdot$ (product). We develop an algebraic system $\\mathsf{S_{RBL}}$ of residuated basic algebra by which we show that $\\mathsf{RBL}$ is a conservative extension of $\\mathsf{BPL}$. We present the sequent formalization $\\mathsf{L_{RBL}}$ o...

Ma, Minghui; Lin, Zhe

2014-01-01

403

A review of active optical devices: II. Phase modulation  

International Nuclear Information System (INIS)

This article presents a review of active optical devices. We examine different technologies that can be used for active wavefront modulation in a large range of applications including displays, electronic paper and adaptive optics. We introduce this review by describing the different light modulations that can be achieved namely amplitude, phase or wavelength modulation. We then examine the different criteria used in order to assess the different technologies and describe in detail each technology including the method of light modulation, its characteristics and applications. The review is divided into two parts: the first one is devoted to amplitude modulation and the second to phase modulation. (topical review)

404

Natural Generalization of Bosonic String Amplitudes  

CERN Document Server

The similarity between tree-level string theory scalar amplitudes, the Koba-Nielsen form ($S^{1}$) and the Virasoro-Shapiro form ($S^{2}$) suggests a natural $S^{n}$ generalization for a scalar amplitude. It is shown that the $S^{n}$ amplitude shares many essential properties of the string theory amplitudes, including $SO(n+1,1)$ conformal symmetry and linear Regge trajectories for the mass spectrum. We also discuss factorization and the critical dimension for the amplitude, which are the necessary conditions for the quantum mechanical consistency (unitarity) of the amplitude.

Natsuume, M

1993-01-01

405

The Action of Adeles on the Residue Complex  

CERN Document Server

Let X be a scheme of finite type over a perfect field k. In this paper we study the relation between two important objects associated to X: the Grothendieck residue complex and the Beilinson adeles complex. It is known that the complex of adeles is a DGA (differential graded algebra). Our first main result is that the residue complex is a right DG module over the adeles complex. The second main result is that the de Rham residue complex is a DG module over the de Rham adeles complex. This action gives rise to the cap product in de Rham (co)homology.

Yekutieli, A

2002-01-01

406

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)

407

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.)

408

One Loop Amplitudes In ABJM  

CERN Document Server

For three dimensional N=6 superconformal field theories we compute one-loop 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; Mauri, Andrea; Penati, Silvia; Santambrogio, Alberto

2012-01-01

409

Neoasozine residues in rice  

International Nuclear Information System (INIS)

Residues of neoasozine in rice grain were determined by neutron activation and colorimetric techniques. Twice application of the chemical before flowering did not lead to increased residue levels while 4-times application resulted in significant increase in the residue level (up to 0.4-0.5 mg/kg). The neutron activation technique was advantageous because of its high sensitivity and the smaller sample amounts required for analysis. The partition ratio of arsenic residues into grain and bran was 73:27 in 100% polished rice. Most of the residue in the bran was transferred to the oilcake fraction. (author)

410

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

411

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

412

Amplitude distribution in the right ventricle  

International Nuclear Information System (INIS)

Amplitude distribution in the right ventricle obtained from ECG-gated ventriculography has been reviewed and six amplitude distribution patterns were identified. Homogeneous distribution was rarely observed even in patients without any cardiac or pulmonary diseases. Furthermore, there was not difference in frequency distribution of the amplitude distribution patterns between the control group, patients with coronary diseases, and those with recent inferior myocardial infarction. It was concluded that amplitude distribution could not be used to detect hypokinetic areas in the right ventricle. (orig.)

413

Amplitudes of 3d Yang Mills Theory  

OpenAIRE

This paper studies various properties of amplitudes in 3d super Yang Mills theory. First we explain how to obtain the amplitudes of 3d super Yang Mills theories from 4d super Yang Mills theories and obtain their helicity structure. Next, we use a 3d BFCW recursion relation to show that the tree amplitudes and loop integrands of maximal 3d super Yang Mills have dual conformal covariance (although not invariance, so that the amplitudes themselves are not dual conformal). Final...

Lipstein, Ae; Mason, L.

2012-01-01

414

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

415

Space-Time Variations in Tidal Stress and Cascadia Tremor Amplitude  

Science.gov (United States)

We present a new analysis of the influence of tidal stresses on the amplitude of non-volcanic tremor in Washington State. Tremor counts (Thomas et al., 2009), tremor amplitude (Rubinstein et al., 2008), and strain (Hawthorne and Rubin, 2010) are modulated by tidal stresses in Cascadia as well as in California. However, tremor amplitudes have not yet been extensively studied in Cascadia. Furthermore, Hawthorne and Rubin's Cascadia-wide tidal stress model (2010) allows us to look at the tremor-tide relationship in more detail than ever before. The ability to look at the tidal modulation of tremor amplitude in space as well as time will increase our understanding of this phenomenon and may provide information about the frictional properties of the plate interface. We focus on the August 2010 episodic tremor and slip (ETS) event recorded by the Array of Arrays, a seismic experiment on the Olympic Peninsula. The instrument response is deconvolved, seismograms band-pass filtered at 1.5-5.5 Hz and envelopes are made in 5-minute windows. An inverse problem compensates for site corrections and source-receiver distances to produce, for any given time, a single amplitude measurement at the source. Source locations are determined using an envelope waveform cross-correlation method. Then, we compare the amplitudes, catalog of tremor locations, and the tidal stress at the desired location and time. Amplitudes during the August 2010 ETS event are clearly modulated by tidal stresses. Viewed in the frequency domain, there are clear peaks in the tremor amplitude spectrum at several tidal periods, most prominently the 12.4 and 24 hour periods. Comparison with Hawthorne and Rubin's tidal stress model shows that higher amplitudes are associated with positive shear stress in the downdip direction and, less strongly, with more compressional normal stress.

Klaus, A. J.; Creager, K. C.; Sweet, J.; Wech, A.

2011-12-01

416

Small amplitude liquid surface sloshing process detected by optical method  

Science.gov (United States)

A laser experimental set up to detect liquid surface sloshing wave excited by the instantaneous momentum was constructed. The sloshing parameters were determined by detecting the scattering light which is modulated by the surface sloshing wave. The analytical expressions which include the relationship between optical intensity and liquid surface sloshing wave and the expressions of the wave length as well as amplitude were derived theoretically. Optical patterns corresponding to static and sloshing liquid surface were obtained experimentally. The sloshing variation process including rising and damping was achieved. Both rising and damping processes are variable exponentially. The rising and damping coefficients and maximum amplitude as well as wavelength of the sloshing wave were also measured experimentally. The detection is nondestructive and real time.

Miao, Yang; Wang, Shaoping

2014-03-01

417

All-fibre source of amplitude-squeezed light pulses  

CERN Document Server

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

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

2004-01-01

418

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

419

Waveform Sampler CAMAC Module  

International Nuclear Information System (INIS)

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

420

Alphaspectroscopic amplitudes for nuclei in the lower half of the sd-shell  

International Nuclear Information System (INIS)

Alpha-spectroscopic amplitudes and factors were calculated with the aid of the shell model for nuclei with mass numbers between A = 16 and A = 24. For transitions to levels belonging to the ground state band of the residual nucleus, the findings confirm the predictions based on the SU(3) model. (orig.)

421

Quantum mechanics without probability amplitudes  

International Nuclear Information System (INIS)

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

422

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

OpenAIRE

The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ ON–OFF keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 d...

Peucheret, Christophe; Lorenzen, Michael Rodas; Seoane, Jorge; Noordegraaf, Danny; Nielsen, Carsten Vandel; Gru?ner-nielsen, Lars; Rottwitt, Karsten

2009-01-01

423

Simulation study of the interaction between large-amplitude HF radio waves and the ionosphere  

OpenAIRE

The time evolution of a large-amplitude electromagnetic (EM) wave injected vertically into the overhead ionosphere is studied numerically. The EM wave has a carrier frequency of 5 MHz and is modulated as a Gaussian pulse with a width of approximately 0.1 milliseconds and a vacuum amplitude of 1.5 V/m at 50 km. This is a fair representation of a modulated radio wave transmitted from a typical high-power HF broadcast station on the ground. The pulse is propagated through the n...

Eliasson, Bengt; Thide?, Bo

2006-01-01

424

Parameters estimation of a noisy sinusoidal signal with time-varying amplitude  

CERN Document Server

In this paper, we give estimators of the frequency, amplitude and phase of a noisy sinusoidal signal with time-varying amplitude by using the algebraic parametric techniques introduced by Fliess and Sira-Ramirez. We apply a similar strategy to estimate these parameters by using modulating functions method. The convergence of the noise error part due to a large class of noises is studied to show the robustness and the stability of these methods. We also show that the estimators obtained by modulating functions method are robust to "large" sampling period and to non zero-mean noises.

Liu, Da-Yan; Perruquetti, Wilfrid

2011-01-01

425

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

426

Binaural modulation detection interference.  

Science.gov (United States)

The ability to detect amplitude modulation (AM) of a tonal probe can be disrupted by the presence of modulated masking tones. Two experiments examined whether a disparity in the interaural parameters of the probe and masker can reduce the amount of interference. In the first experiment, the effects of interaural time and intensity differences were studied in separate sets of conditions. With low-frequency carriers, the detection of 10-Hz probe modulation in the presence of 10-Hz masker modulation was not significantly affected by interaural time differences. With higher-frequency carriers, dichotic stimuli were generated through combinations of diotic, dichotic, or monotic probe and masker presentations in which the probe and masker did not share a common interaural intensity difference. In these conditions, the amount of interference was affected by the interaural configuration. However, monotic level differences between the probe and masker may have contributed to the effect of interaural configuration. In the second experiment, the probe and masker were presented through separate speakers in an enclosed listening environment. Spatial separation between the sources for the probe and masker led to a small reduction in the amount of interference. When the masker modulation rate was varied with the probe AM rate fixed at 10 Hz, the extent of tuning in the modulation domain in the sound-field conditions was similar to that obtained with diotic stimulus presentation over headphones. PMID:9301056

Sheft, S; Yost, W A

1997-09-01

427

Vector Modulator for Phase Shifting in Passive Beamforming Wireless Systems  

OpenAIRE

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

P.Sampath,; Gunavathi, K.

2010-01-01

428

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

CERN Document Server

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

Karjanto, N; Peterson, P

2011-01-01

429

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

430

Pesticide residues in eagles  

Science.gov (United States)

Bald and golden eagles found sick or dead in 18 States and Canada during 1964-1965 were analyzed for pesticide residues. Residues in bald eagles were considerably higher than in golden eagles. Residues of DDE, DDD, and dieldrin were detected in all samples of bald eagle carcasses; other compounds found, less frequently were heptachlor epoxide, endrin, and DCBP, a metabolite of DDT. DDE was detected in all samples of golden eagle carcasses; DDD, DDT, dieldrin, and heptachlor epoxide were detected less frequently.

Reichel, W.L.; Cromartie, E.; Lamont, T.G.; Mulhern, B.M.; Prouty, R.M.

1969-01-01

431

Higher-order solitons in amplitude-disordered waveguide arrays  

Science.gov (United States)

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

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

2014-10-01

432

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

433

Chlorine Analysis - Water. Training Module 5.260.2.77.  

Science.gov (United States)

This document is an instructional module package prepared in objective form for use by an instructor familiar with the procedures for chlorine residual analysis. It includes objectives, an instructor guide, and student handouts. The module addresses the determination of combined and free residual chlorine in water supply samples using three…

Kirkwood Community Coll., Cedar Rapids, IA.

434

On the Integrand-Reduction Method for Two-Loop Scattering Amplitudes  

CERN Document Server

We propose a first implementation of the integrand-reduction method for two-loop scattering amplitudes. We show that the residues of the amplitudes on multi-particle cuts are polynomials in the irreducible scalar products involving the loop momenta, and that the reduction of the amplitudes in terms of master integrals can be realized through polynomial fitting of the integrand, without any apriori knowledge of the integral basis. We discuss how the polynomial shapes of the residues determine the basis of master integrals appearing in the final result. We present a four-dimensional constructive algorithm that we apply to planar and non-planar contributions to the 4- and 5-point MHV amplitudes in N=4 SYM. The technique hereby discussed extends the well-established analogous method holding for one-loop amplitudes, and can be considered a preliminary study towards the systematic reduction at the integrand-level of two-loop amplitudes in any gauge theory, suitable for their automated semianalytic evaluation.

Mastrolia, Pierpaolo

2011-01-01

435

Circular polarization modulation for digital communication systems  

OpenAIRE

Conventional approaches of digital modulation schemes make use of amplitude, frequency and/or phase as modulation characteristic to transmit data. In this paper, we exploit circular polarization (CP) of the propagating electromagnetic carrier as modulation attribute which is a novel concept in digital communications. The requirement of antenna alignment to maximize received power is eliminated for CP signals and these are not affected by linearly polarized jamming signals. The work presents t...

Abidin, Zu; Xiao, P.; Amin, M.; Fusco, V.

2012-01-01

436

The relative phonetic contributions of a cochlear implant and residual acoustic hearing to bimodal speech perception.  

Science.gov (United States)

The addition of low-passed (LP) speech or even a tone following the fundamental frequency (F0) of speech has been shown to benefit speech recognition for cochlear implant (CI) users with residual acoustic hearing. The mechanisms underlying this benefit are still unclear. In this study, eight bimodal subjects (CI users with acoustic hearing in the non-implanted ear) and eight simulated bimodal subjects (using vocoded and LP speech) were tested on vowel and consonant recognition to determine the relative contributions of acoustic and phonetic cues, including F0, to the bimodal benefit. Several listening conditions were tested (CI/Vocoder, LP, T(F0-env), CI/Vocoder + LP, CI/Vocoder + T(F0-env)). Compared with CI/Vocoder performance, LP significantly enhanced both consonant and vowel perception, whereas a tone following the F0 contour of target speech and modulated with an amplitude envelope of the maximum frequency of the F0 contour (T(F0-env)) enhanced only consonant perception. Information transfer analysis revealed a dual mechanism in the bimodal benefit: The tone representing F0 provided voicing and manner information, whereas LP provided additional manner, place, and vowel formant information. The data in actual bimodal subjects also showed that the degree of the bimodal benefit depended on the cutoff and slope of residual acoustic hearing. PMID:22280613

Sheffield, Benjamin M; Zeng, Fan-Gang

2012-01-01

437

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

438

Agricultural pesticide residues  

International Nuclear Information System (INIS)

The utilization of tracer techniques in the study of agricultural pesticide residues is reviewed under the following headings: lysimeter experiments, micro-ecosystems, translocation in soil, degradation of pesticides in soil, biological availability of soil-applied substances, bound residues in the soil, use of macro- and microautography, double and triple labelling, use of tracer labelling in animal experiments. (U.K.)

439

Abelian modules  

Directory of Open Access Journals (Sweden)

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

S. Hal?c?o?lu

2009-08-01

440

On Discrete Fourier Spectrum of Randomly Modulated Signals  

Science.gov (United States)

In this work the problem of characterization of Discrete Fourier Transform (DFT) spectrum of an original complex-valued signal modulated by random fluctuations of amplitude and phase is investigated. It is assumed that the amplitude and phase of signal values at discrete time moments of observations are distorted by adding realizations of independent and identically distributed random variables. The obtained results of theoretical analysis of such distorted signal spectra show that only in the case of amplitude modulation the DFT spectrum of the modulated bounded signal can be similar to the original signal spectrum, although there occur random deviations. On the other hand, if phase modulation is present, then the DFT spectrum of the modulated bounded signal not only shows random deviations but also amplitudes of peaks existing in the original spectrum are diminished, and consequently similarity to the original signal spectrum can be significantly blurred.

Popi?ski, Waldemar

2010-01-01