Modification Of Amplitude Research Articles

Key preprocessing technology and its application for CBM AVO analysis

The hazards of amplitude versus offset (AVO) technique mostly applied in seismic explorations for predicting coalbed methane (CBM) content mainly derive from multi-stage amplitude modifications during seismic signal preprocessing. The modifications are undoubtedly necessitated by improving high signal-to-noise ratio (SNR) and high resolution, and achieve high fidelity to some extent; and nevertheless lead to an unfavorable possibility to implement CBM AVO analysis. Similar to sandstone reservoir with gas, AVO analysis preprocessing for CBM reservoir strictly abides by a relative amplitude preserved (RAP) principle and particularly emphasizes on preserving the evanescent class IV AVO anomaly. As for those indispensable dealings with linear noise attenuations, near-surface variety compensations and time/depth spatial imaging, the key technologies adapted to CBM AVO preprocessing should use radial trace (RT) filter, refined surface-consistent amplitude compensation (SCAC), and RAP Kirchhoff prestack time migration (PSTM). The theoretical analysis and one real 3D example in this paper demonstrate that three key technologies compliant to RAP principle in CBM AVO preprocessing can preserve the class IV AVO anomaly and benefit an operation of CBM AVO analysis and an improvement of CBM evaluation.

Precise signal amplitude retrieval for a non-homogeneous diagnostic beam using complex interferometry approach

Classical interferometry became widely used method of active optical diagnostics. Its more advanced version, allowing reconstruction of three sets of data from just one especially designed interferogram (so called complex interferogram) was developed in the past and became known as complex interferometry. Along with the phase shift, which can be also retrieved using classical interferometry, the amplitude modifications of the probing part of the diagnostic beam caused by the object under study (to be called the signal amplitude) as well as the contrast of the interference fringes can be retrieved using the complex interferometry approach. In order to partially compensate for errors in the reconstruction due to imperfections in the diagnostic beam intensity structure as well as for errors caused by a non-ideal optical setup of the interferometer itself (including the quality of its optical components), a reference interferogram can be put to a good use. This method of interferogram analysis of experimental data has been successfully implemented in practice. However, in majority of interferometer setups (especially in the case of the ones employing the wavefront division) the probe and the reference part of the diagnostic beam would feature different intensity distributions over their respective cross sections. This introduces additional error into the reconstruction of the signal amplitude and the fringe contrast, which cannot be resolved using the reference interferogram only. In order to deal with this error it was found that additional separately recorded images of the intensity distribution of the probe and the reference part of the diagnostic beam (with no signal present) are needed. For the best results a sufficient shot-to-shot stability of the whole diagnostic system is required. In this paper, efficiency of the complex interferometry approach for obtaining the highest possible accuracy of the signal amplitude reconstruction is verified using the computer generated complex and reference interferograms containing artificially introduced intensity variations in the probe and the reference part of the diagnostic beam. These sets of data are subsequently analyzed and the errors of the signal amplitude reconstruction are evaluated.

Modification of Dynamic Foundation Response Due to Soil-Structure Interaction

ABSTRACTThis paper presents the results from extensive parametric dynamic analyses of soil-structure systems that focus on the clear modification (increase or decrease) of the acceleration amplitude at the foundation with respect to the free-field, especially for squatty structures. Properties of the systems are selected such as to cover a wide range of meaningful geometries and materials for engineering practice. The results are presented in terms of weighted modification factors of the maximum foundation acceleration amplitude with reference to the corresponding maximum acceleration amplitude at free-field, for squatty and more slender structures. For the large majority of the studied systems, foundation acceleration decreases from the free-field by 10–15% on average. Nevertheless, acceleration demand at the foundation increases compared to the free-field, for 30% of squatty and for 15% of the more slender structures. Modification of the foundation acceleration amplitude is also correlated with the ratio of the predominant period of the input motion to the flexible-base system period. Finally, the findings of this study are compared with sparse available recorded data from the Seismic Hazard Harmonization in Europe database.

Kinematic analysis of the scapula after total anatomic and reverse shoulder arthroplasty

Scapular motion is essential for full, functional mobility of the arm. Many shoulder pathologies are associated with alterations of scapular kinematics which have been only little studied in total shoulder arthroplasties. The aim of this study was to compare the 3D scapula kinematics in two groups of patients with total shoulder anatomic (aTSA) or reverse (rTSA) arthoplasties to asymptomatic controls of comparable age during two arm elevation tasks (abduction and flexion) and two simulations of activity of daily living (“hair combing” and “back washing”). Scapular kinematics was assessed using a Polhemus Fastrak electromagnetic device in 14 patients with aTSA (and 14 controls) and 9 patients with rTSA (and 9 controls). The 3D rotations and the 3D displacements of the barycenter of the scapula were measured at 30°, 60° and 90° of humero-thoracic (HT) elevation. Patient groups were compared with each other by Mann–Whitney U test and with their respective controls by Wilcoxon test. Scapulohumeral rhythm was reduced in both patient groups as compared with controls. Patients with aTSA showed more lateral rotation and more linear displacements of the scapula compared to rTSA and control groups. Nevertheless, the global kinematics pattern remained unchanged in both groups of patients. Patients showed a greater participation of the scapula in HT elevation movements and kinematic modifications of small amplitude that could suggest a compensation mechanism for patients with aTSA. However, having a total shoulder arthroplasty does not alter the global kinematic pattern of the scapula.

Nonlinearity-induced time-varying harmonic dynamic axle load and its impact on dynamic stability of car–trailer combinations

ABSTRACTA nonlinearity-induced time-varying harmonic dynamic axle load is found in the road test of a car–trailer combination. To understand its influence on system dynamic stability, a corresponding linear single-track model (STM) is proposed. System dynamic stability is described and sensitivity analysis for the system parameters is achieved. The contribution of the harmonic force is quantified by a derived effective axle load. Because the harmonic effect might be time varying in practice, a time–frequency analysis-based parameter identification method is introduced. Experimental study shows that a time-varying harmonic effect really exists. A yaw-rate-based simulation method is designed to simulate this behaviour. The sensitivity analysis of the influence of the harmonic amplitude or phase on dynamic stability is performed with a simulation study. With appropriate modification of the harmonic amplitude and phase shift applied in selected time windows, the time-varying system characteristics in the road test can be simulated very well.

Wavelet‐domain audio watermarking using optimal modification on low‐frequency amplitude

On the basis of the Karush–Kuhn–Tucker (KKT) theorem, a novel digital audio watermarking scheme is proposed. To guarantee the robustness of a watermark, this scheme embeds information into low-frequency coefficients of audio's discrete wavelet transform. For the modification of low-frequency amplitude, this study uses the KKT theorem to minimise the difference between the original and the watermarked coefficients. Accordingly, embedding strength is increased to enhance the most robustness of a watermarked audio under sufficient embedding capacity and audio quality. In addition, the proposed watermarking scheme can extract the hidden data without the knowledge of original audio signal. Experimental results indicate that the performance of the proposed scheme is mostly better than other amplitude modification methods.

Effective Response Modifications of Non-Proportionally Damped Resonating Structures

The structural resonance properties of damped structures can be exploited to obtain a required dynamic response with relatively low input power requirements. Practical applications often demand temporary modifications of this response. This paper presents a systematic approach to modify the response of harmonically driven, non-proportionally damped resonating structures using local structural property changes and excitation adjustments. The complex response is written in polar form (i.e., modulus and argument) to enhance insights. Sensitivity analysis is used to approximate the influence of the control variables on the response. A projection is proposed to determine the locations at which a specific structural change scores maximum effect to reach the desired response modifications. The introduced response normalization separates amplitude and shape modifications in a clear way. This work shows response modifications of non-proportionally damped resonating structures due to control variables in an intuitive manner.

Two-dimensional spectral interpretation of time-dependent absorption near laser-coupled resonances

We demonstrate a two-dimensional time-domain spectroscopy method to extract amplitude and phase modifications of excited atomic states caused by the interaction with ultrashort laser pulses. The technique is based on Fourier analysis of the absorption spectrum of perturbed polarization decay. An analytical description of the method reveals how amplitude and phase information can be directly obtained from measurements. We apply the method experimentally to the helium atom, which is excited by attosecond-pulsed extreme ultraviolet light, to characterize laser-induced couplings of doubly excited states.

Delayed Effects of Corticosterone on Slow After-Hyperpolarization Potentials in Mouse Hippocampal versus Prefrontal Cortical Pyramidal Neurons

The rodent stress hormone corticosterone changes neuronal activity in a slow and persistent manner through transcriptional regulation. In the rat dorsal hippocampus, corticosterone enhances the amplitude of calcium-dependent potassium currents that cause a lingering slow after-hyperpolarization (sAHP) at the end of depolarizing events. In this study we compared the putative region-dependency of the delayed effects of corticosterone (approximately 5 hrs after treatment) on sAHP as well as other active and passive properties of layer 2/3 pyramidal neurons from three prefrontal areas, i.e. the lateral orbitofrontal, prelimbic and infralimbic cortex, with the hippocampus of adult mice. In agreement with previous studies, corticosterone increased sAHP amplitude in the dorsal hippocampus with depolarizing steps of increasing amplitude. However, in the lateral orbitofrontal, prelimbic and infralimbic cortices we did not observe any modifications of sAHP amplitude after corticosterone treatment. Properties of single action potentials or % ratio of the last spike interval with respect to the first spike interval, an indicator of accommodation in an action potential train, were not significantly affected by corticosterone in all brain regions examined. Lastly, corticosterone treatment did not induce any lasting changes in passive membrane properties of hippocampal or cortical neurons. Overall, the data indicate that corticosterone slowly and very persistently increases the sAHP amplitude in hippocampal pyramidal neurons, while this is not the case in the cortical regions examined. This implies that changes in excitability across brain regions reached by corticosterone may vary over a prolonged period of time after stress.

Extracting Phase and Amplitude Modifications of Laser-Coupled Fano Resonances

Fano line shapes observed in absorption spectra encode information on the amplitude and phase of the optical dipole response. A change in the Fano line shape, e.g., by interaction with short-pulsed laser fields, allows us to extract dynamical modifications of the amplitude and phase of the coupled excited quantum states. We introduce and apply this physical mechanism to near-resonantly coupled doubly excited states in helium. This general approach provides a physical understanding of the laser-induced spectral shift of absorption-line maxima on a sub-laser-cycle time scale as they are ubiquitously observed in attosecond transient-absorption measurements.

Gênese e ontogênese do ritmo de sono/vigília em humanos

Living organisms undergo changes over time, which can be seen along years, one day or several hours. Biological rhythms are understood as cyclical fluctuations observed in the living matter and present an endogenous component which is influenced by the environment. The expression of these rhythms and its relation to the environment also changes along the individual’s life, as we observe with sleep/wake patterns. In this article we present a review about the development of sleep/wake rhythm throughout life, describing the consolidation process of a synchronized circadian rhythm along childhood, the phase changes of sleep/wake cycle along adolescence and, afterwards, its phase and amplitude modifications in the elderly, focusing the interaction with environmental cyclical factors

Perturbing the potential vorticity field in mesoscale forecasts of two Mediterranean heavy precipitation events

ABSTRACTIn order to improve the quality of the Mediterranean high-impact weather (HIW) numerical predictions, this study proposes to modify the potential vorticity (PV) field of the model initial state, taking advantage of information provided by the water vapour (WV) channel of the METEOSAT-7 satellite. The implemented PV field modifications aim to reduce the mismatch between the upper-level PV features and the WV brightness temperatures guided by the known relation between these two fields (PV-WV technique). The PV-WV technique effectiveness is evaluated on two HIW events, and is also compared with two additional PV modification techniques from an earlier study. The chosen episodes occurred on 9–10 June 2000 and 9–10 October 2002 and produced heavy precipitation over both Spain and France. The main difference between these two episodes is found in the driving mechanism, a mesoscale cyclone for the June 2000 event and a larger low-pressure centre for the October 2002 case. The two additional PV modification techniques introduce perturbations along the zones highlighted by the MM5 adjoint model calculated sensitivity zones (PV-adjoint) and along the three-dimensional PV structure presenting the locally most intense values and gradients of the field (PV-gradient). A close examination of both case studies of the forecast rainfall fields and several objective verification indices show that the PV-WV technique performance exceeds the control (or non-perturbed) forecast skill while remaining inside the distribution obtained by both PV-gradient and PV-adjoint techniques. This PV-WV technique could be used to increase the ensemble spread introducing higher amplitude modifications. Thus, a more skilled ensemble prediction system could be built by taking advantage of the subjectivity inherent to this method (manual perturbations) and also of the uncertainty present in the initial state.

Single-photon double ionization of H2away from equilibrium: A showcase of two-center electron interference

We demonstrate the effect of two-center interference on single-photon double ionization [double photoionization (DPI)] of the aligned H${}_{2}$ molecule when it shrinks or expands from the equilibrium internuclear distance. This interference affects the first stage of the DPI process in which the primary photoelectron is ejected predominantly along the polarization axis of light and its geometrical interference factor is most sensitive to the internuclear distance in the parallel ($\ensuremath{\Sigma}$) orientation of the internuclear and polarization axes. This effect is responsible for strong modification of the DPI amplitude in the parallel orientation while the corresponding amplitude for the perpendicular ($\ensuremath{\Pi}$) orientation is rather insensitive to the internuclear distance. The combination of these two factors explains the profound kinetic energy release effect on the fully differential cross sections of DPI of H${}_{2}$.

Uroguanylin Promotes Eletroencephalographic Changes in Rat Brain

Uroguanylin (UGN) is an STa‐like peptide that acts on membrane guanylate cyclase receptors of intestine and kidney, regulating electrolyte and water epithelial transport. Recent reports demonstrate the expression of guanylate cyclase C in the central nervous system. We have probed the effect of UGN administered through intracisternal infusion of this peptide at the concentrations of 2.5μM/ min and 7.5 μM/min in order to evaluate modifications of mean absolute amplitude of electroencephalographic spectra (EEG), number of spikes and sharp waves per minute, as well as absolute amplitude of those spikes and sharp waves of the EEG in anesthetized Wistar rats. Uroguanylin or saline administration lasted for 30 minutes and previously to that, EEG was recorded during 10 min and throughout the infusion periods, with another 10 min EEG registration at the final phase of the protocol. The present results demonstrate that 2.5 and 7.5 μM/min intracisternal infusion of UGN significantly enhances mean absolute amplitude of spikes and sharp waves (p=0.03). There was also an increase in the number of spikes and sharp waves per minute. No statistical significance was observed on absolute alpha and theta spectra amplitude. The present data suggest that UGN acts on bioelectrogenesis of cortical cells by inducing hypersynchronic firing of neurons. This effect was blocked by nedocromil, suggesting that UGN acts by increasing the activity of chloride channels and points out for the presence of a possible functional guanylin receptor in the brain, as demonstrated recently (Gong et al., Science. 2011,333:1642–6).

Phenomenology of psychogenic movement disorders in children

Psychogenic movement disorders are heterogeneous and diagnostically challenging. Despite the growing literature on adult forms, clinical features in children have received relatively little attention. We retrospectively reviewed medical records and video of patients <18 years diagnosed with a psychogenic movement disorder at our institute between 2007 and 2010. We identified 14 patients (6 males and 8 females) with a mean onset age of 11.5 years. Levels of diagnostic confidence were documented (2 patients), clinically established (8 patients), and probable (4 patients). A single movement disorder was present in 10 patients (71%); 4 patients (29%) presented an association of two or more movement disorders. Eleven patients presented other medically unexplained symptoms associated with their movement disorders. Five patients, among 6 with chronic occurrence, performed a polymyographic study showing significant modifications of frequency, amplitude, and distribution of electromyographic activity, related to distracting maneuvers. The present series represents 5% of all movement disorders observed in the considered period and 32% of nonorganic neurological manifestations. The most frequent movement disorders were tremor (36%) and dystonia (29%). We describe two phenotypes not previously reported among psychogenic movement disorders: myoclonus and association of myoclonus with dystonia. We remark on the presence of psychogenic symptoms associated with movement disorders (79%) as being one of the most useful clinical clues as well as on the value of polymyographic study in chronic psychogenic movement disorders, which provide evidence of the inconsistency of movement disorders.

Infrasound production by bolides: A global statistical study

We have examined a dataset consisting of 71 bolides detected by satellite sensors, which provide energy and location estimates, with simultaneous measurements of the same events on 143 distinct waveforms. These bolides have total source energies ranging from 0.02kt TNT equivalent yield to ≈20kt and probable diameters of order a few meters on average. We find that it is possible to detect large events with energies of ≈20kt or more globally. Infrasonic detections of these events for stratospheric arrivals have ranges between 350–17,000km and show clear wind-related amplitude modifications. We find that our period–yield relations are virtually identical to that found from AFTAC nuclear test data with the most robust period–yield correlation found for those events having multiple station averaged periods. We have also found empirical expressions relating maximum expected detection range for infrasound as a function of energy and low and high frequency cut-off as a function of energy. Our multi-variate fits suggest that 12 yield-scaling is most appropriate for long range bolide infrasound measurements with a distance scaling exponent of ≈1.1 best representing the data. Our best-fit wind correction exponent is a factor of ≈3 smaller than found by previous studies which we suggest may indicate a decrease in the value of k with range. We find that the integral acoustic efficiency for bolides is ≥0.01% with a best lower limit estimate nearer 0.1%. Finally, we conclude that a range independent atmosphere implementation of the normal-mode approach to simulate bolide amplitudes is ineffective at large ranges due to the large change in atmospheric conditions along source-receiver paths.

Effect of a fluid challenge on the Surgical Pleth Index during stable propofol–remifentanil anaesthesia

The Surgical Pleth Index (SPI), derived from pulse amplitude and heartbeat interval, is proposed to monitor anti-nociception during anaesthesia. Its response to noxious stimulation can be affected by the intravascular volume status. This study investigated the effect of a fluid challenge (FC) on SPI during steady-state conditions. After Institutional Review Board approval, 33 consenting patients undergoing neurosurgery received a 4 ml/kg starch FC over less than 5 min under stable surgical stimulation conditions and stable propofol (Ce(PPF) ) and remifentanil (Ce(REMI) ) effect-site concentrations as estimated by target-controlled infusion systems. Intravascular volume status was assessed using the Delta Down (DD). We looked at the SPI response to FC according to DD, Ce(PPF) , and Ce(REMI) . Following FC, SPI did not change in 16, increased in 12, and decreased in 3 patients. Ce(REMI) poorly affected the SPI response to FC. In normovolaemic patients, the probability of an SPI change after FC was low under common Ce(PPF) (0.9 to 3.9 μg/ml). A decrease in SPI was more probable with worsening hypovolaemia and lowering Ce(PPF) , while an increase in SPI was more probable with increasing Ce(PPF) . SPI changes were only attributable to modifications in pulse wave amplitude and not in heart rate. During stable anaesthesia and surgery, SPI may change in response to FC. The effect of FC on SPI is influenced by volaemia and Ce(PPF) through pulse wave amplitude modifications. These situations may confound the interpretation of SPI as a surrogate measure of the nociception-anti-nociception balance.

Pure haploinsufficiency for Dravet syndrome NaV1.1 (SCN1A) sodium channel truncating mutations

Dravet syndrome (DS), a devastating epileptic encephalopathy, is mostly caused by mutations of the SCN1A gene, coding for the voltage-gated Na(+) channel Na(V)1.1 α subunit. About 50% of SCN1A DS mutations truncate Na(V)1.1, possibly causing complete loss of its function. However, it has not been investigated yet if Na(V)1.1 truncated mutants are dominant negative, if they impair expression or function of wild-type channels, as it has been shown for truncated mutants of other proteins (e.g., Ca(V) channels). We studied the effect of two DS truncated Na(V)1.1 mutants, R222* and R1234*, on coexpressed wild-type Na(+) channels. We engineered R222* or R1234* in the human cDNA of Na(V)1.1 (hNa(V)1.1) and studied their effect on coexpressed wild-type hNa(V)1.1, hNa(V)1.2 or hNa(V)1.3 cotransfecting tsA-201 cells, and on hNa(V)1.6 transfecting an human embryonic kidney (HEK) cell line stably expressing this channel. We also studied hippocampal neurons dissociated from Na(V)1.1 knockout (KO) mice, an animal model of DS expressing a truncated Na(V)1.1 channel. We found no modifications of current amplitude coexpressing the truncated mutants with hNa(V)1.1, hNa(V)1.2, or hNa(V)1.3, but a 30% reduction coexpressing them with hNa(V)1.6. However, we showed that also coexpression of functional full-length hNa(V)1.1 caused a similar reduction. Therefore, this effect should not be involved in the pathomechanism of DS. Some gating properties of hNa(V)1.1, hNa(V)1.3, and hNa(V)1.6 were modified, but recordings of hippocampal neurons dissociated from Na(V)1.1 KO mice did not show any significant modifications of these properties. Therefore, Na(V)1.1 truncated mutants are not dominant negative, consistent with haploinsufficiency as the cause of DS. We have better clarified the pathomechanism of DS, pointed out an important difference between pathogenic truncated Ca(V)2.1 mutants and hNa(V)1.1 ones, and shown that hNa(V)1.6 expression can be reduced in physiologic conditions by coexpression of hNa(V)1.1. Moreover, our data may provide useful information for the development of therapeutic approaches.

Effect of strain on the orbital and magnetic ordering of manganite thin films and their interface with an insulator

We study the effect of uniform uniaxial strain on the ground state electronic configuration of a thin film manganite. Our model Hamiltonian includes the double-exchange, the Jahn-Teller electron-lattice coupling, and the antiferromagnetic superexchange. The strain arises due to the lattice mismatch between an insulating substrate and a manganite which produces a tetragonal distortion. This is included in the model via a modification of the hopping amplitude and the introduction of an energy splitting between the Mn e_g levels. We analyze the bulk properties of half-doped manganites and the electronic reconstruction at the interface between a ferromagnetic and metallic manganite and the insulating substrate. The strain drives an orbital selection modifying the electronic properties and the magnetic ordering of manganites and their interfaces.

Wavelet Transforms to Probe the Torsional Modes of a Thermally Excited Cantilever across the Jump-to-Contact Transition: Preliminary Results

The response of the torsional modes of a thermally excited cantilever across the jump-to-contact transition shows a modification of the oscillation amplitude, frequency, and damping. The measurement of these parameters is important because their analysis provides nanoscale information on the physical, chemical, and topographic properties of the sample. The tip-surface interaction potential is usually reconstructed by Fourier analysis of the cantilever oscillations around its equilibrium position. However, Fourier analysis can be correctly interpreted only in the case of stationary systems. The wavelet transform analysis overcomes these limitations, revealing the temporal evolution of the spectral content of a temporal trace. The one-dimensional time signal from the photodiode is converted into a two-dimensional time-frequency topography, which simultaneously exhibits the time and frequency behavior of the cantilever thermal fluctuations. In the present study, we show preliminary data obtained using wavelet transforms to analyze thermally excited torsional cantilever modes during jump-to-contact transition on a highly oriented pyrolitic graphite surface in air. [DOI: 10.1380/ejssnt.2011.228]