Beating Effect Research Articles

Effect of premature ventricular beats on manual and automatic repolarization measurements

Objective: To compare QT interval and QT dispersion in ventricular ectopic beats with measurements from the preceding and the immediately following sinus beats, and investigate differences between manual and automatic measurements. Patients: Eleven chronic uremic patients. Main outcome measures: ECGs were recorded during hemodialysis treatment and 12-lead sections containing five consecutive beats were extracted, each containing four sinus beats and one centrally-positioned premature ventricular beat. QT measurements were performed both manually and with a computer-automated technique. Results: T wave amplitude was greater in the ectopic beats compared to the sinus beats (0.61 ± 0.18 vs. 0.23 ± 0.06 mV, P <.001). The ectopic beats had a greater QT than the sinus beats when measured manually (415 ± 35 ms vs. 386 ± 28 ms, P <.001), or automatically (375 ± 30 vs. 366 ± 27 ms, P<.01). The sinus beats following the ectopics had a greater QT than the preceding sinus beats (400 ± 27 vs. 386 ± 28 ms, P<.001, manual; 382 ± 24 vs. 366 ± 27 ms, P<.001, automatic). Differences in QT dispersion were seen only between the ectopic and sinus beats (91 ± 31 vs. 58 ± 27 ms, P <.001, manual; 68 ± 33 vs. 49 ± 35 ms, P <.001, automatic). Conclusions: Manual measurement resulted in greater QT values than automatic measurement. Both techniques identified differences between sinus and ectopic beats. The ventricular ectopic beats resulted in an increase in the QT of the immediately following sinus beats. These results confirm the need to interpret QT measurements with care in the presence of ectopic beats.

Sound Synthesis of the Harpsichord Using a Computationally Efficient Physical Model

A sound synthesis algorithm for the harpsichord has been developed by applying the principles of digital waveguide modeling. A modification to the loss filter of the string model is introduced that allows more flexible control of decay rates of partials than is possible with a one-pole digital filter, which is a usual choice for the loss filter. A version of the commuted waveguide synthesis approach is used, where each tone is generated with a parallel combination of the string model and a second-order resonator that are excited with a common excitation signal. The second-order resonator, previously proposed for this purpose, approximately simulates the beating effect appearing in many harpsichord tones. The characteristic key-release thump terminating harpsichord tones is reproduced by triggering a sample that has been extracted from a recording. A digital filter model for the soundboard has been designed based on recorded bridge impulse responses of the harpsichord. The output of the string models is injected in the soundboard filter that imitates the reverberant nature of the soundbox and, particularly, the ringing of the short parts of the strings behind the bridge.

Quantum beats in hydrogen and antihydrogen atoms in an external electric field.

An effect of quantum beats that arises due to the coherent excitation of 2s and 2p states of hydrogen and antihydrogen atoms in an external electric field is described. It is shown that the quantum beat signal contains terms linear in electric field, i.e., is of opposite sign for the hydrogen and antihydrogen atoms. The conditions for the observation of this effect are discussed.

Dynamics of excited m-dichlorobenzene

Dynamics of excited m -dichlorobenzene is investigated in real time by femtosecond pump-probe method, combined with time-of-flight mass spectrometric detection in a supersonic molecular beam. The yields of the parent ion and daughter ion C 6 H 4 Cl + are examined as a function of the delay between the 270 and 810 nm femtosecond laser pulses, respectively. The lifetime of the first singlet excited state S 1 of m -dichlorobenzene is measured. The origin of this daughter ion C 6 H 4 Cl + is discussed. The ladder mechanism is proposed to form the fragment ion. In addition, our experimental results exhibit a rapid damped sinusoidal oscillation over intermediate time delays, which is due to quantum beat effects.

On the beating of ASE and XPM noise in optical receivers

Presents a theoretical study on the effects of beating between amplified spontaneous emission (ASE) noise and cross-phase modulation (XPM)-induced noise in optical receivers. Our theory of ASE-XPM beat noise predicts that such beating effects are actually beneficial to receiver performance, resulting in lower error probabilities. The ASE-XPM beat noise produces skewed non-Gaussian probability distributions and shifts optimum receiver threshold closer to the one level. These conclusions are insensitive to the exact noise statistics assumed for XPM or ASE.

Quantum beat phenomenon due to polaritons in dispersive and photonic band gap materials

The quantum beats phenomenon due to polaritons has been studied in dispersive materials and photonic band gap materials doped with a three-level atom. It is considered that the atom is in top and middle excited states and the spontaneous emission of the radiation field from the top excited state to the ground state and the middle excited state to the ground state is allowed. The following interesting results are found in the present paper. When two excited states of the atom lie outside the band gap of these materials, there is an emission of two polaritons from the upper and the middle excited states to the ground state. These two polaritons interfere and produce the quantum beats effect. But when the upper state lies within the band gap and the middle state lies either within the band gap or outside the band gap, the quantum beat effect disappears.

Quantum beat phenomenon due to polaritons in dispersive and photonic band gap materials

Abstract The quantum beats phenomenon due to polaritons has been studied in dispersive materials and photonic band gap materials doped with a three-level atom. It is considered that the atom is in top and middle excited states and the spontaneous emission of the radiation field from the top excited state to the ground state and the middle excited state to the ground state is allowed. The following interesting results are found in the present paper. When two excited states of the atom lie outside the band gap of these materials, there is an emission of two polaritons from the upper and the middle excited states to the ground state. These two polaritons interfere and produce the quantum beats effect. But when the upper state lies within the band gap and the middle state lies either within the band gap or outside the band gap, the quantum beat effect disappears.

Acoustical differences between pre-Columbian Mexican aerophones

This paper discusses Mesoamerican musical instruments that produce special sounds and noises. The types of musical instruments to be discussed and demonstrated include those that (a) produce animal sounds; (b) allow performers to exploit multiphonic and beat effects; and (c) allow performers to produce microtonal and polyphonic effects. Examples are shown of simple flutes, vessel flutes, and whistles of Aztec, Mixtec, Mayan, Olmec, and other pre-Colombian cultures. (To be presented in Spanish.)

Destruction of the Beating Effect¶for a Non-Linear Schrödinger Equation

We consider a non-linear perturbation of a symmetric double-well potential as a model for molecular localization. In the semiclassical limit, we prove the existence of a critical value of the perturbation parameter giving the destruction of the beating effect. This value is twice the one corresponding to the first bifurcation of the fundamental state. Here we make use of a particular projection operator introduced by G. Nenciu in order to extend to an infinite dimensional space some known results for a two-level system.

The Effect of Beating and Missing Analysts' Forecasts on the Information Content of Unexpected Earnings

This study investigates whether the market rewards (penalizes) firms for meeting (not meeting) analysts' earnings forecasts. Specifically, we examine the market response to positive and negative forecast errors. In addition, we examine whether the sensitivity of stock prices to positive or negative forecast errors is affected by the firms' history of consistently beating or missing analysts' forecasts. The results indicate that the earnings multiple applied to positive unexpected earnings is significantly greater than for negative unexpected earnings. In addition, we find that after controlling for the magnitude of the forecast error and bad news preannouncements, the market penalty for missing forecasts is significantly greater in absolute terms than the response to beating forecasts. We document evidence that, while the market recognizes and partially discounts the systematic component of positive analysts' forecast errors, a higher multiple is attached to the unsystematic component of unexpected earnings of firms that consistently beat analysts' forecasts. Overall, the evidence suggests that the increasing frequency of positive forecast errors as documented in previous research is a rational response by managers to market-related incentives.

Theoretical Models for Calculating the Kinetics of Luminescence Spectra with Allowance for the Effect of Quantum Beats under Molecular Isomerization

On the basis of the previously developed approach to the description of molecular transformations we propose two theoretical models for analyzing the process of intramolecular energy dissipation with allowance for the nonradiative isomer‐isomer transitions. Examples of kinetic curves for the level populations as functions of time in the presence of quantum beats associated with isomerization are given.

Inter-fiber bonding effects of beating, starch or filler

Inter-fiber bonding effects of beating, starch or filler

Listening in the dark: Behavioral and neural mechanisms of acoustic recognition in a singing fish

Vocalizing species of teleost fish have a simple repertoire of species-typical signals central to their social and reproductive behavior. Male midshipman fish (‘‘the California singing fish’’) acoustically court females using ‘‘hums’’ that are long duration (secs 1h) and spectrally simple. Individual hums exhibit an essentially flat envelope consisting of a low fundamental frequency (90–100 Hz) and several harmonics. By contrast, naturally occurring acoustic beats show envelope modulations: the hums of neighboring males overlap to produce a beat with a difference frequency (0–8 Hz) in which amplitude and phase modulations result from the continual shifting of the two fundamental frequencies. Behavioral playback (phonotaxis) studies show that individual midshipman can use multiple signal parameters including hum duration, gap duration between successive hums, fundamental frequency, and intensity to distinguish hums from each other, while the effectiveness of beats as playback signals depends upon both beat modulation rates and depth of modulation. Neurophysiological evidence shows that auditory neurons in the midshipmans VIIIth nerve and midbrain encode the physical attributes of these signals mainly using spike rate and spike synchronization, mechanisms that we propose contribute to the neural templates adapted for both hum and beat recognition. [Research supported by NIH.]

Magnetic-field-dependent interplay between incoherent and Fermi liquid transport mechanisms in low-dimensional τ-phase organic conductors

We present an electrical transport study of the two-dimensional (2D) organic conductor $\ensuremath{\tau}\ensuremath{-}[\mathrm{P}\ensuremath{-}(S,S)\ensuremath{-}\mathrm{DMEDT}\ensuremath{-}\mathrm{TTF}{]}_{2}({\mathrm{AuBr}}_{2})$ $({\mathrm{AuBr}}_{2}{)}_{y}$ (where $y\ensuremath{\sim}0.75)$ at low temperatures and high magnetic fields. The interplane resistivity ${\ensuremath{\rho}}_{\mathrm{zz}}$ increases with decreasing temperature, with the exception of a slight anomaly at 12 K. Under a magnetic field B, both ${\ensuremath{\rho}}_{\mathrm{zz}}$ and the in-plane resistivity plane ${\ensuremath{\rho}}_{\mathrm{xx}}$ show a pronounced negative and hysteretic magnetoresistance. In spite of a negative residual resistivity ratio in zero field, Shubnikov--de Haas (SdH) oscillations are observed in some (high quality) samples above 15 T. Furthermore, contrary to the single closed orbit Fermi surface (FS) predicted from band structure calculations (where a single star-shaped FS sheet with an area of $\ensuremath{\sim}12.5%$ of ${A}_{\mathrm{FBZ}}$ is expected), two fundamental frequencies ${F}_{l}$ and ${F}_{h}$ are detected in the SdH signal. These orbits correspond to $2.4$ and $6.8%$ of the area of the first Brillouin zone ${(A}_{\mathrm{FBZ}}),$ with effective masses ${\ensuremath{\mu}}_{l}=4.4\ifmmode\pm\else\textpm\fi{}0.5$ and ${\ensuremath{\mu}}_{h}=7.5\ifmmode\pm\else\textpm\fi{}0.1,$ respectively. The angular dependence, in tilted magnetic fields, of ${F}_{l}$ and ${F}_{h},$ reveals a 2D character of the FS, but no evidence for warping along the ${k}_{z}$ direction (e.g., the absence of a beating effect in the SdH signal) is observed. Angular dependent magnetoresistance (AMRO) further suggests a FS which is strictly 2D where the interplane hopping ${t}_{c}$ is virtually absent or incoherent. The Hall constant ${R}_{\mathrm{xy}}$ is field independent, and the Hall mobility ${\ensuremath{\mu}}_{H}$ increases by a factor of $\ensuremath{\sim}3$ under moderate magnetic fields. Hence the field does not alter the carrier concentration, even in the presence of a large negative magnetoresistance, but only increases the lifetime ${\ensuremath{\tau}}_{s}.$ Our observations suggest a unique physical situation where a stable 2D Fermi liquid state in the molecular layers, are incoherently coupled along the least conducting direction. The magnetic field not only reduces the inelastic scattering between the 2D metallic layers, as seen in the large negative magnetoresistance and SdH effect, but it also reveals the incoherent nature of the interplane transport in the AMRO spectrum. Finally, the observed Fermi surface is at odds with band structure calculations. The observation of small pockets may suggest FS reconstruction. However, the very flat bands in the electronic structure, combined with the variable charge transfer, may be the origin of these effects. The apparent ferromagnetic character of the hysteresis in the magnetoresistance, remains an unsolved problem.

Coherent crosstalk impairments in polarization multiplexed transmission due to polarization mode dispersion

Coherent crosstalk mechanisms induced by polarization mode dispersion in polarization multiplexed fiber transmission are examined by systems experiments, analysis and supporting modeling. Primary mechanisms include destructive interference, edge effects, and beat effects, leading to pulse distortion and to bit-error-rate penalties. Rules of thumb for tolerable crosstalk levels are developed.

Ultrasonic treatment to improve the quality of recycled pulp fiber

The effect of ultrasound on the quality of recycled fibers was investigated. Ultrasound was applied to recycled pulp fiber suspension before ink removal by conventional flotation. The ultrasonic treatment induced an increase in the sedimentation volume of the fiber, which implies that the flexibility and bulkiness of the fiber increase. The water retention value of the ultrasonically treated fiber recovered from the loss caused by the recycling. These facts are due to a beating effect of the treatment. The paper sheets prepared from the ultrasonically treated fiber suspension showed higher sheet density, tensile strength, and brightness than that from an untreated fiber suspension. The process, which consists of ultrasonic treatment for 1 min following flotation deinking, requires about 1.4 times as much energy as the conventional flotation deinking process, but it induced 20% improvement in brightness. The results indicate that the ultrasonic treatment is effective in improving recycled fiber quality.

Effect of refractive index in optical particle sizing by using spatial frequency method

Investigation of optical particle sizing by using spatial frequency method was conducted by analytical and experimental methods. An equation to determine the optimized optical observation angles for different relative refractive indices of media was derived. The sensitivity of the spatial frequency varying with the relative refractive index of media and the polarization angle of the incident beams was simulated by using generalized Lorenz–Mie theory (GLMT) [Gouesbet et al., Localized interpretation to compute all the coefficients g n m in the generalized Lorenz–Mie theory, J. Opt. Soc. Am. A, 7 (6) (1990) 998–1007 [1]; Gouesbet, Generalized Lorenz–Mie theory and applications, Part. Part. Syst. Charact., 11 (1994) 22–34]. It was found that a large observation angle has very little effect on the spatial frequency. The relationship between the spatial frequency and the particle diameter has been successfully described. Experimental study was conducted to measure the light scattered from a spherical particle and it demonstrated that the spatial frequency of the fringe pattern is uniquely dependent on the particle diameter at a certain scattering angle. This study also demonstrated that the beating effect between the refractive and the reflective rays can be ignored which was a critical issue for the conventional laser phase-Doppler anemometry. By using fast Fourier transform, the spatial frequency can be measured accurately.

Spin beats of anisotropic excitons in GaSe

Temporal development of polarized luminescence signals in GaSe was investigated in a magnetic field. Reflecting the quantum beat effect between the Zeeman split exciton states, it was found that oscillatory features appear on the degree of circular or linear polarization of the luminescence. Different exciton g factors were observed in longitudinal and transverse magnetic fields, showing the magneto-optical anisotropy of the present sample.

Zero-field spin splitting in InAs-AlSb quantum wells revisited

We present magnetotransport experiments on high-quality InAs-AlSb quantum wells that show a perfectly clean single-period Shubnikov-de Haas oscillation down to very low magnetic fields. In contrast to theoretical expectations based on an asymmetry induced zero-field spin splitting, no beating effect is observed. The carrier density has been changed by the persistent photo conductivity effect as well as via the application of hydrostatic pressure in order to influence the electric field at the interface of the electron gas. Still no indication of spin splitting at zero magnetic field was observed in spite of highly resolved Shubnikov- de Haas oscillations up to filling factors of 200. This surprising and unexpected result is discussed in view of other recently published data.

Isotope beating effects in the analysis of polymer distributions by Fourier transform mass spectrometry

For Fourier transform mass spectrometry analysis of high mass ions, the signals from closely spaced isotope peaks undergo periodic destructive interference, producing a beat pattern in the time-domain signal. The mass spectra that are obtained by sampling transient signals for less than two beat periods exhibit an error in the relative abundances that are measured. This effect is shown to cause significant errors in the measurement of the relative abundances of the components of polymer distributions, leading to errors in the derived average molecular weights for such samples. Computer simulations show that isotope beating causes this error to increase as the duration of an acquired transient becomes short compared to the beating period. This error becomes insignificant when the transient is acquired for longer than twice the beat period. Experimental data are presented for polymers in which an oligomeric distribution of monoisotopic peaks is produced by stored waveform inverse Fourier transform ejection of all 13C-containing isotope peaks. The data show that the isotope beating-induced abundance errors are eliminated when there are no isotope peaks present.