Discrete Amplitude Research Articles

Monochromatic infrasonic tremor driven by persistent degassing and convection at Villarrica Volcano, Chile

Infrasonic data collected at Villarrica volcano (Chile) in March 2009 show a sustained, continuous, infrasonic oscillation (tremor) with a monochromatic low frequency content at ∼0.75 Hz. This tremor is extremely stable in time both at the summit and at a distal (∼4 km) small aperture array. Infrasonic tremor is characterized by discrete high amplitude bursts with a cyclic recurrence time of ∼40 s and is well correlated (0.93) with seismic tremor. These new data are compared with previous datasets collected in 2002 and 2004 during different levels of activity. All data show the same persistent infrasonic tremor and have the same strong correlation with seismic tremor. The stability and correlation of infrasonic and seismic tremor indicate the existence of a sustained and continuous process, which we suggest is related to the gravity‐driven bubble column dynamics responsible for conduit convection.

IMPROVED VOLTAGE OF CASCADED INVERTERS USING SINE QUANTIZATION PROGRESSION

The previous methods of cascaded multilevel inverter (CMLI) can improve power quality but the methods have low voltage output if the DC voltages limited by the voltage rating of power semiconductor. To improve the amplitude of CMLI output voltage, this paper proposes a new DC voltage progression. The progression based on sine quantization method (SQM), which determines a sequence of DC voltages from discrete amplitudes of sine wave function. The method also collaborates with step equal residual area method (SERAM) to minimized total harmonics distortions (THD). A single-phase CMLI that consist four H-Bridges simulated and implemented to verify the methods. Amplitude output voltage and THD results of simulations and experiments indicate that the sine quantization progression produce the highest output voltage than other DC voltage progressions, with power quality or THD in the accepted region. The amplitude of output voltage have linier function with amplitude equal 0.6665 times of HBridges numbers and have exponential function of THD with value below 5%.

Latest Permian (Changhsingian) to Early Triassic (Induan-Olenekian) of the Mt Goodwin Sub-group at Blacktip gas field, southeastern Bonaparte Basin, Australia

Gas was discovered in intra-Mt Goodwin Sub-group sandstones (Ascalon Formation) of the southeastern Bonaparte Basin in Blacktip–1 in 2001 from a zone characterised by a discrete seismic amplitude anomaly. This integrated study uses wireline logs, cores, cuttings, palynology, micropaleontology and geochemical analyses to determine the depositional environment of the Mt Goodwin Sub-group reservoirs and the source rock potential of this large, latest Permian (Changhsingian) to Early Triassic (Induan Olenekian) section of the Bonaparte Basin in northern Australia. Specific outcomes include a better understanding of the Early Triassic reservoir sandstone depositional environment and recognition of marker horizons on electric logs and seismic profiles, resulting in a more consistent regional interpretive framework for the uppermost Permian (Changhsingian) and Early Triassic (Induan Olenekian), in the Bonaparte Basin.

Catheter ablation of atrial fibrillation guided by complex fractionated atrial electrogram mapping of atrial fibrillation substrate

Cardiologists and physicians have witnessed a significant change in the management of atrial fibrillation (AF): antiarrhythmic agents are no longer considered more effective than just merely using compounds that control ventricular response of the arrhythmia with anticoagulation in high-risk patients. Catheter ablation has grown into wider acceptance as an important therapeutic modality in treating tachyarrhythmias. And over the past decade, several studies have clearly established that catheter ablation of atrial fibrillation is safe and effective and is an important alternative therapeutic option to the pharmacological approach. In general, there are two approaches to AF ablation: The anatomical approach, the most popular one, relies on isolation of electrical connections of all four pulmonary veins to the left atrium with or without adjuvant ablations, i.e. additional linear ablations. The second approach is the electrogram-guided approach by mapping and targeting areas of complex fractionated atrial electrograms (CFAE) which is the main topic of this review. The myriad pathologies leading to and resulting from AF have led to many theories regarding how substrate should be defined and how to reconcile substrate ablation with trigger ablation. The identification of spatiotemporally stable areas of very low amplitude short cycle length CFAE in a sea of otherwise discrete normal amplitude and relatively longer cycle length electrograms led to ablate the CFAE as a marker of abnormal substrate. This pure substrate-based ablation strategy has resulted in remarkable success, including mortality benefit, even in high-risk patients with very long standing persistent AF. In this review, we discuss in detail the prevailing mechanisms underlying CFAE, how to map and ablate CFAE sites, correlation of CFAE areas to those of ganglionic plexi, clinical outcomes of the approach, and the role of CFAE in the hybrid approach of AF ablation using a combination of pulmonary vein isolation and targeting CFAE areas.

Improving the methodology for spectral analysis of climatic time series

The paper discusses a methodology able to estimate both the discrete and continuous spectra without any assumption on the shape of spectral densities. The approach to estimate the spectral density is based on a robust smoothing of the periodogram. Bandwidth, a quantity similar to the width of spectral windows traditionally used in spectral analysis, is estimated locally in contrast to intuitively chosen global window lengths. Detection and estimation of frequencies forming discrete spectra are also addressed. The procedure is applied to Central England temperature (CEt), North Atlantic Oscillation (NAO) index and Oxygen Isotope of North Greenland Ice Core Project (δ18O of NGRIP) data. Annual and half annual cycles were detected in CEt data, whilst 118.2- and 41.7-ky cycles were found in δ18O of NGRIP. This latter periodicity is almost as intense as the dominant longer cycle. Several local peaks of spectral densities were recognised in each time series that mostly cover earlier results. However, a few previous findings at low frequencies have not been reinforced by the present method. Identification of modest local peaks or discrete amplitudes at low frequencies is an extremely challenging task as climatic data generally have spectral densities rising to low frequencies.

Mapping the Position of DNA Polymerase-Bound DNA Templates in a Nanopore at 5 Å Resolution

DNA polymerases are molecular motors that catalyze template-dependent DNA replication, advancing along template DNA by one nucleotide with each catalytic cycle. Nanopore-based measurements have emerged as a single molecule technique for the study of these enzymes. Using the alpha-hemolysin nanopore, we determined the position of DNA templates bearing inserts of abasic (1',2'-dideoxy) residues, bound to the Klenow fragment of Escherichia coli DNA polymerase I (KF) or to bacteriophage T7 DNA polymerase. Hundreds of individual polymerase complexes were analyzed at 5 A precision within minutes. We generated a map of current amplitudes for DNA-KF-deoxynucleoside triphosphate (dNTP) ternary complexes, using a series of templates bearing blocks of three abasic residues that were displaced by approximately 5 A in the nanopore lumen. Plotted as a function of the distance of the abasic insert from n = 0 in the active site of the enzyme held atop the pore, this map has a single peak. The map is similar when the primer length, the DNA sequences flanking the abasic insert, and the DNA sequences in the vicinity of the KF active site are varied. Primer extension catalyzed by KF using a three abasic template in the presence of a mixture of dNTPs and 2',3'-dideoxynucleoside triphosphates resulted in a ladder of ternary complexes with discrete amplitudes that closely corresponded to this map. An ionic current map measured in the presence of 0.15 M KCl mirrored the map obtained with 0.3 M KCl, permitting experiments with a broader range of mesophilic DNA and RNA processing enzymes. We used the abasic templates to show that capture of complexes with the KF homologue, T7 DNA polymerase, yields an amplitude map nearly indistinguishable from the KF map.

Reverse propagation of T waves from the Emperor seamount chain

Analysis of seismo‐acoustic T waves associated with an intermediate‐depth earthquake beneath northern Japan reveals that the detected T waves are secondary waves scattered by distant seamounts. The timing of T‐wave onset, 3000 s after occurrence of the earthquake, indicates that the detected T waves did not follow a direct path from the solid‐liquid conversion point near the Japan Trench to the observation stations in northeast Japan. It is hypothesized that the original T waves were reverse‐scattered back toward Japan by peaks of the Emperor seamount chain after propagation in the northern Pacific Ocean. The synthesized envelope patterns for acoustics scattered at the seamounts considering this multi‐path effect reproduce the travel time and amplitude pattern of the observed T waves well, with each seamount group producing a discrete amplitude peak of the scattered wave. These observations suggest that topographical obstructions act as a secondary source for T‐wave propagation in the ocean.

Effect of sound amplitude on the acoustic attenuation characteristics of Helmholtz resonators.

Influence of sound amplitude on the acoustic attenuation performance of a Helmholtz resonator is investigated computationally. Time‐dependent and compressible flow field is determined by solving two‐dimensional unsteady, turbulent, and compressible Navier–Stokes equations through an implicit and noniterative pressure‐implicit‐splitting‐of‐operators algorithm. The solution of full Navier–Stokes equations remedies the constraints in small‐amplitude‐wave treatments, thereby allowing a proper modeling of nonlinearities due to large amplitudes. Transmission loss of the Helmholtz resonator is then calculated for discrete inlet amplitudes using the pressure obtained from the flow field. Higher amplitudes are shown in this study to reduce the peak transmission loss significantly.

Manometric evaluation of jejunal limb after total gastrectomy and Roux-Orr anastomosis for gastric cancer

Total gastrectomy with Roux-Orr anastomosis is frequently performed for gastric cancer. Since intestinal motility of the Roux limb has never been evaluated after this operation, pressure activity was investigated in the Roux limb of ten patients (aged 51-77 years) who had undergone total gastrectomy and Roux-Orr reconstruction. Investigations were carried out during a 6-h fast and 3 h after a 605 kcal mixed meal. During fasting only two patients had activity fronts and these were abnormal. All ten patients displayed non-propagating bursts of contractions and three had discrete clustered contractions and high amplitude jejunal contractions. The fed state was characterized by a severely reduced motor activity pattern and other abnormalities. Total gastrectomy with Roux-Orr anastomoses provokes a relatively severe disturbance in intestinal activity.

Propagation and collision of compacton-like kinks in Klein–Gordon lattice system

We study the propagation and collision of the compacton-like kinks in the system of an anharmonic lattice with a double well on-site potential by a direct algebraic method and numerical experiments. It is found that the localization of the compacton-like kinks is related to the nonlinear coupling parameter Cnl and the potential barrier height V0 of the double well potential. The velocity of the propagation of the compacton-like kinks is determined by the linear coupling parameter Cl, the nonlinear coupling parameter Cnl and the localization parameter q. Numerical experiments demonstrate that appropriate Cl is not detrimental to a stable propagation of the compacton-like kinks. However, the collision of compacton-like kinks and anti-kinks in the lattice with comparatively small Cl leads to the emergence of a discrete stationary breather and small amplitude nonlinear oscillation background, while moderate Cl results in the emergence of two deformed kinks with radiating oscillations and lower propagation velocities.

Complete direct method for electron-hydrogen scattering: Application to the collinear and Temkin-Poet models

We present an efficient generalization of the exterior complex scaling (ECS) method to extract discrete inelastic and ionization amplitudes for electron-impact scattering of atomic hydrogen. This fully quantal method is demonstrated over a range of energies for the collinear and Temkin-Poet models and near-threshold ionization is examined in detail for singlet and triplet scattering. Our numerical calculations for total ionization cross sections near threshold strongly support the classical threshold law of Wannier [Phys. Rev. 90, 817 (1953)] (σ∝E1.128±0.004) for the L=0 singlet collinear model and the semiclassical threshold law of Peterkop [J. Phys. B 16, L587 (1983)] (σ∝E3.37±0.02) for the L=0 triplet collinear model, and are consistent with the semiclassical threshold law of Macek and Ihra [Phys. Rev. A 55, 2024 (1997)] (σ∝exp[(-6.87±0.01)E-1/6]) for the singlet Temkin-Poet model.

Phase regression approach for estimating the parameters of a noisy multifrequency signal

A novel approach for estimating the parameters of a multifrequency signal from discrete samples corrupted by additive noise is presented. An established mathematical model indicates that noise influence on the discrete phase and amplitude spectra is equivalent to additive phase and amplitude noise, respectively. On this basis, a simple algorithm is proposed to estimate the frequency and phase of each sinusoid component by linear regression on the phase spectra of segmented signal blocks, while an amplitude estimator is directly derived from the spectrum of the window function. The circular nature of the phase spectrum is thoroughly explored. Also, an algorithmic scheme is presented. The derived variances of the estimators show that for a noisy signal this approach provides superior accuracy over the traditional approaches. Simulations and engineering application confirm the validity of the presented method.

One-bit second order sigma-delta modulator including a polynomial vector quantizer

A circuit for determining a discrete amplitude of a set of samples x k s comprising two integrators that produce integrated signals u k and v k , a converter which supplies an input to the first integrator, timing elements which produce delayed signals u k−1 and v k−1 , and a vector quantizer Q(x k , u k−1 , v k−1 ) configured to provide a binary output as a function of samples x k and the integrated signals u k−1 and v k−1 .

Microwave photonic vector modulator for high-speed wireless digital communications

The authors present the design, realization, and experimental results of a microwave/photonic circuit suitable for high-speed direct digital modulation of microwave signals. The modulator employs a combination of microwave, photonic, and digital techniques to produce a discrete phase and amplitude (i.e., vector) modulated carrier signal. The proof-of-concept demonstration presented in this paper was performed using a carrier frequency of 1 GHz and supports BPSK, QPSK, and 16-QAM. The authors also discuss ways to modify the modulator to simultaneously achieve data rates on the order of several hundreds of Mbs and wideband frequency hopping.

Stability of one-dimensional array solitons.

The array soliton stability in the discrete nonlinear Schrödinger equation with dispersion for periodic boundary conditions is studied. The linear growth rate dependence on the discrete wave number and soliton amplitude is calculated from the linearized eigenvalue problem using the variational method. In addition, the eigenvalue problem is solved numerically by shooting method and a good agreement with the analytical results is found. It is proved numerically that the results for the instability threshold for the circular array coincides with the quasicollapse threshold for the case of open arrays with initial pulses in a form of array solitons.

Formation of the Intensity Distribution in Laser Beams due to Difraction on Structures of Small-Size Optical Inhomogeneities

The possibilities of formation of the intensity distribution in laser beams due to diffraction of radiation on spatial structures of small-size optical inhomogeneities are considered. Computer modeling of beam profile formation by plates-apodizers containing two-dimensional structures of discrete amplitude or phase scatterers is performed. The results presented testify to the prospects of optical elements with scattering centers for laser beam shaping in UV, visible, and IR spectral ranges.

Two-dimensional Fourier transform rheology

A two-dimensional Fourier transformation (FT) rheology experiment is presented that separates the relaxation dynamics of different contributions to the stress relaxation, here specifically for entangled polymers. This experiment has the overall form of discrete large amplitude oscillations and consists of multiple step shear experiments. It is called large amplitude step shear oscillations, LASSO. The time-dependent nonlinear material response follows the discrete periodic excitation and can therefore be Fourier transformed, which results in a spectrum of harmonics for each delay time between the steps. The FT is used here to correlate the different step shear experiments. The method was applied to a slightly entangled, polydisperse polyisobutylene solution where a small deviation of the time strain separation is detected, even at times exceeding the Rouse time by orders of magnitude. On the other hand, the time temperature superposition seems to work for all the harmonic decays within the spectrum. When the time window between the shear steps is reduced such that slow relaxation processes still possess memory of prior steps, an increase of the nonlinear contributions of the fast, completely relaxed, relaxation modes is observed. This is in qualitative agreement with reptation models where polymer stretching and orienting are considered coupled processes.

Fiber Fourier optics

The Fourier transform of a coherent optical image can be evaluated physically by use of a single lens plus free-space propagation, thereby providing the basis for the field of Fourier optics. I point out that one can similarly evaluate the discrete Fourier transform of a sampled or pixelated optical array physically by passing the discrete array amplitudes through a network of single-mode fibers or optical waveguides. A passive optical network that evaluates the fast Fourier transform of a coherent array can be fabricated by use of (N/2)log(2)[N] optical 3-dB couplers plus small added phase shifts. Implementing such networks in fiber or integrated optical form could provide the basis for a possible technology of fiber Fourier optics.

Elementary receptor currents elicited by a single pheromone molecule exhibit quantal composition.

Responses to single pheromone molecules, elementary receptor currents (ERC), recorded from antennal olfactory receptor neurones of the moth Bombyx mori were studied in situ, at the opened sensilla, using the voltage-clamp technique in transepithelial recordings. The amplitude parameters of the ERCs eliciting one action potential in the bombykol and bombykal receptor neurones were analysed. The ERC amplitude varied largely within a range of 0.5-5.5 pA. The amplitude histograms of the ERCs exhibited a series of peaks and shoulders. Quantal analysis of the amplitude distributions based on spectral methods revealed that a quantum event underlies the ERCs. Deconvolution of the ERC amplitude distributions using the distribution of baseline noise indicates that the ERCs exhibit discrete amplitude levels. The weighted average interval between the levels indicates that the quantal size is 0.6-0.7 pA.

Residual noise reduction in sign algorithm

The residual noise of the sign algorithm can be reduced by adding a uniformly distributed noise (dithering) to the sign algorithm input signal. In this paper, a simple equation for the residual noise reduction factor (RNRF) is derived for the case in which the noise in the sign algorithm input signal has a two-level discrete amplitude distribution. It is demonstrated that the RNRF is proportional to the ratio between the amplitude of the input noise and the adaptation step.