Modification Of Amplitude Research Articles

Escape mechanism of a self-trapped topological soliton

The adiabatic minimum-energy path of a self-trapped topological soliton is computed for trans-polyacetylene using the Su-Schrieffer-Heeger Hamiltonian and ab initio methods. The frequently cited activation barrier via a ridge shift of the hypertangent order parameter overestimates its true value by 14 orders of magnitude. Self-trapped solitons migrate along the Goldstone mode direction with continuously adjusted amplitudes so that a small-width soliton expands and a large-width soliton shrinks when they move uphill. A soliton with the critical width may migrate without any amplitude modifications. In an open chain as solitons move from the chain center toward a chain edge, the minimum-energy path first follows a tilted washboard landscape and then increases exponentially at the edge.

Including lateral velocity variations into true-amplitude common-shot wave-equation migration

In heterogeneous media, standard one-way wave equations describe only the kinematic part of one-way wave propagation correctly. For a correct description of amplitudes, the one-way wave equations must be modified. In media with vertical velocity variations only, the resulting true-amplitude one-way wave equations can be solved analytically. In media with lateral velocity variations, these equations are much harder to solve and require sophisticated numerical techniques. We present an approach to circumvent these problems by implementing approximate solutions based on the one-dimensional analytic amplitude modifications. We use these approximations to show how to modify conventional migration methods such as split-step and Fourier finite-difference migrations in such a way that they more accurately handle migration amplitudes. Simple synthetic data examples in media with a constant vertical gradient demonstrate that the correction achieves the recovery of true migration amplitudes. Applications to the SEG/EAGE salt model and the Marmousi data show that the technique improves amplitude recovery in the migrated images in more realistic situations.

Electrostatic structures associated with dusty electronegative magnetoplasmas

By using the hydrodynamic equations of positive and negative ions, the Boltzmann electron density distribution and the Poisson equation with stationary dust, a three-dimensional (3D) Zakharov–Kuznetsov (ZK) equation is derived for small but finite amplitude ion-acoustic waves. However, the ZK equation is not appropriate to describe the system either at critical plasma compositions or in the vicinity of the critical plasma compositions. Therefore, the modified ZK (MZK) and extended ZK (EZK) equations are derived. The generalized expansion method is used to analytically solve the ZK, MZK and EZK equations. A new class of solutions that admits a train of well-separated bell-shaped periodic pulses is obtained. In certain conditions, the latter degenerates to either solitary or shock wave solutions. The effects of the physical parameters on the nonlinear structures are examined in many plasma environments having different negative ion species, such as D- and F-regions of the Earth's ionosphere, as well as in laboratory plasma experiments. Numerical analysis of the solutions revealed that the profile of the nonlinear pulses suffers amplitude and width modifications due to enhancement of the dust practices, negative ions, positive-to-negative ion mass ratio and positive/negative ion cyclotron frequency. Furthermore, the necessary conditions for both solitons and shocks propagation as well as their polarity are examined.

Distortion of HBT Images by Meson Clouds

We study the effects of mesonic final state interactions on the Hanbury Brown and Twiss (HBT) intensity interferometry for mesons in ultra-relativistic heavy ion collisions. The modification of the one-body amplitude of emitted mesons while going through a cloud of other mesons is estimated in the semiclassical approximation with a mesonic optical potential which incorporates both coherent forward scattering with other mesons and the absorption due to incoherent scattering in the meson cloud. We show how these effects result in the distortion of the HBT images.

Mislocalization of Flashed and Stationary Visual Stimuli after Adaptation of Reactive and Scanning Saccades

When we look around and register the location of visual objects, our oculomotor system continuously prepares targets for saccadic eye movements. The preparation of saccade targets may be directly involved in the perception of object location because modification of saccade amplitude by saccade adaptation leads to a distortion of the visual localization of briefly flashed spatial probes. Here, we investigated effects of adaptation on the localization of continuously visible objects. We compared adaptation-induced mislocalization of probes that were present for 20 ms during the saccade preparation period and of probes that were present for >1 s before saccade initiation. We studied the mislocalization of these probes for two different saccade types, reactive saccades to a suddenly appearing target and scanning saccades in the self-paced viewing of a stationary scene. Adaptation of reactive saccades induced mislocalization of flashed probes. Adaptation of scanning saccades induced in addition also mislocalization of stationary objects. The mislocalization occurred in the absence of visual landmarks and must therefore originate from the change in saccade motor parameters. After adaptation of one type of saccade, the saccade amplitude change and the mislocalization transferred only weakly to the other saccade type. Mislocalization of flashed and stationary probes thus followed the selectivity of saccade adaptation. Since the generation and adaptation of reactive and scanning saccades are known to involve partially different brain mechanisms, our results suggest that visual localization of objects in space is linked to saccade targeting at multiple sites in the brain.

Arbitrary waveform synthesis by multiple harmonics generation and phasing in aperiodic optical superlattices

The process of generating periodic optical waveforms includes the generation and phasing of several harmonics of a fundamental frequency. In this work, we show that simultaneous generation and phasing of the harmonics can be performed in a monolithic aperiodic optical superlattice (AOS). Stable periodic waveforms can thus be delivered to a predetermined location by simply sending a laser beam through a properly designed and fabricated AOS crystal. A detailed mathematical description for generating the domain pattern in such an AOS crystal is given and the process is numerically demonstrated. The waveform that is generated from a monolithic AOS is highly reproducible and phase stable. We also use propagation in air as an example to show how any predictable phase and amplitude modifications such as air dispersion that will alter the desired waveform can be pre-compensated in the design phase of the AOS crystal.

The Abnormal Recovery Cycle of Somatosensory Evoked Potential Components in Children with Migraine can be Reversed by Topiramate

The aim of this study was to compare the recovery cycle of somatosensory evoked potentials (SEPs) in children with migraine without aura before and after treatment with topiramate. Eleven migraine children were studied before and after a 3-month treatment with topiramate at the average dose of 1.3 mg/kg/day. We calculated the SEP latency and amplitude modifications after paired electrical stimuli at 5, 20 and 40 ms interstimulus intervals, comparing them with a single stimulus condition assumed as baseline. In nine patients, who had a significant reduction in headache frequency after treatment, the recovery cycles of the P24 (P = 0.03) and N30 (P < 0.005) potentials were longer after than before topiramate treatment. In two migraineurs who did not show any improvement, the recovery cycles of the cortical SEP components were even shorter after treatment. Our results suggest that topiramate efficacy in paediatric migraine prophylaxis is probably related to restored cortical excitability.

$ \alpha$ -nucleus elastic scattering in the energy range 25-70 MeV/nucleon

Working within the framework of the Coulomb-modified Glauber model for nucleus-nucleus collisions, we analyse the elastic scattering of \( \alpha\) -particles on 4He at 25, 30, 35, 40, 50, and 70MeV/nucleon. Emphasis has been put on the parametrization of the basic (input) NN amplitude that preserves the low-q behavior at the desired energy, whereas the higher momentum transfer components are treated phenomenologically. The analysis also considers the medium modification of the NN amplitude due to Pauli blocking. Using the realistic form factors for colliding nuclei, it is found that the data are reproduced satisfactorily well up to the fairly large value of momentum transfer. We also discuss the suitability of the extracted NN amplitude for other target nuclei in the energy range under consideration. Our analysis suggests that the proper account of the higher momentum transfer components of the NN amplitude may push down the Glauber model to lower energies, and increase its validity in the region of relatively large momentum transfers.

Coulomb-nuclear interference in pion-nucleus bremsstrahlung

Pion-nucleus bremsstrahlung offers a possibility of measuring the structure functions of pion-Compton scattering from a study of the small-momentum-transfer region where the bremsstrahlung reaction is dominated by the single-photon-exchange mechanism. The corresponding cross-section distribution is characterized by a sharp peak at small momentum transfers. But there is also a hadronic contribution which is smooth and constitutes an undesired background. In this communication the modification of the single-photon exchange amplitude by multiple-Coulomb scattering is investigated as well as the Coulomb-nuclear interference term.

Dépression et rythmes circadiens

Adverse changes in circadian rhythms are an integral part of the clinical features of endogenous depression, and particularly of seasonal depression. Alongside twenty-four variations in the major symptoms, these forms of depression can be characterised psychometrically, physiologically and biologically. The most classical adverse changes are amplitude modifications, fluctuations and periodicity of the hormonal secretory rhythms. Pathophysiological and psychopathological models have been proposed to combat these abnormalities. The leading models include free course, phase advance (or instability) and hypnic models, or those based on disturbances of the internal clock. The main psychopathological models are those of endokinesis and psychosocial desynchronisation. The therapeutic applications of the pathophysiological models use manipulation of the wake-sleep cycle, phototherapy and melatonin and its derivatives : those of the psychopathological models used time-space management and development of resynchronisation capacities. The question determining whether these adverse changes are a cause or effect of depressive behaviour is unresolved.

Transient Bevacizumab (Avastin)-Induced Alterations in Rat Eyes

Aims: To study the histopathological, biochemical and functional effects of intravitreal bevacizumab on the rat eye, with special emphasis on its immediate pro-inflammatory features eventually associated with cellular oxidative burden. Methods: Histopathological evaluation was performed 24 h, 1 and 4 weeks after bevacizumab (75 μg/rat eye) or saline intravitreal injection, as well as biochemical analysis of oxidative stress-related markers and electroretinograms. Results: Bevacizumab induces a transient inflammatory reaction together with a modification of the b-wave amplitude and latency of the electroretinogram. No changes were observed in any of the oxidative stress markers studied at any time after injection. Conclusion: Intravitreal bevacizumab injection per se generates an immediate, transient and mild inflammation of the rat eye, which is not associated with oxidative stress in ocular tissues.

The role of combined consonant duration and amplitude processing on speech intelligibility in noise

Reduced speech intelligibility in noise, especially consonant perception, is a well documented phenomenon. Research in clear speech has revealed many acoustic and phonetic differences between speech spoken in a conversational versus clear-speech mode. In the present study two components were tested in combination, namely increases in consonant duration (and respective decreases in adjacent vowel duration) and selective-consonant amplification. Conditions in which intelligibility improvements were observed for the individual processing of duration and amplitude modifications were chosen and tested in combination. The components were applied to Hearing-in-Noise Test sentences and consonant-vowel (CV) pairs. Stimuli were presented in sound field to normal-hearing individuals in the presence of speech-shaped noise. Percent correct was measured for HINT sentences and confusion matrices were developed for the CV pair intelligibility tests. An information transmission analysis was performed. Results will be discussed with regard to the greater body of research in clear speech.

Both Gi and Go Heterotrimeric G Proteins Are Required to Exert the Full Effect of Norepinephrine on the β-Cell KATP Channel

The effects of norepinephrine (NE), an inhibitor of insulin secretion, were examined on membrane potential and the ATP-sensitive K+ channel (K ATP) in INS 832/13 cells. Membrane potential was monitored under the whole cell current clamp mode. NE hyperpolarized the cell membrane, an effect that was abolished by tolbutamide. The effect of NE on K ATP channels was investigated in parallel using outside-out single channel recording. This revealed that NE enhanced the open activities of the K ATP channels approximately 2-fold without changing the single channel conductance, demonstrating that NE-induced hyperpolarization was mediated by activation of the K ATP channels. The NE effect was abolished in cells preincubated with pertussis toxin, indicating coupling to heterotrimeric G i/G o proteins. To identify the G proteins involved, antisera raised against alpha and beta subunits (anti-G alpha common, anti-G beta, anti-G alpha i1/2/3, and anti-G alpha o) were used. Anti-G alpha common totally blocked the effects of NE on membrane potential and K ATP channels. Individually, anti-G alpha i1/2/3 and anti-G alpha o only partially inhibited the action of NE on K ATP channels. However, the combination of both completely eliminated the action. Antibodies against G beta had no effects. To confirm these results and to further identify the G protein subunits involved, the blocking effects of peptides containing the sequence of 11 amino acids at the C termini of the alpha subunits were used. The data obtained were similar to those derived from the antibody work with the additional information that G alpha i3 and G alpha o1 were not involved. In conclusion, both G i and G o proteins are required for the full effect of norepinephrine to activate the K ATP channel.

Motor Cortical Disinhibition During Early and Late Recovery After Stroke

Background. Functional neuroimaging studies show adaptive changes in areas adjacent and distant from the stroke. This longitudinal study assessed whether changes in cortical excitability in affected and unaffected motor areas after acute stroke correlates with functional and motor recovery. Methods. We studied 13 patients with moderate to severe hemiparesis 5 to 7 days (T1), 30 days (T2), and 90 days (T3) after acute unilateral stroke, as well as 10 healthy controls. We used paired-pulse transcranial magnetic stimulation to study intracortical inhibition and facilitation, recording from the bilateral thenar eminences. F waves were also recorded. Results. At T1, all patients showed significantly reduced intracortical inhibition in the unaffected hemisphere. At T2, in patients whose motor function recovered, intracortical inhibition in the unaffected hemisphere returned to normal. In patients with poor clinical motor recovery, abnormal disinhibition persisted in both hemispheres. At T3, in patients whose motor function progressively recovered, the abnormal disinhibition in the unaffected hemisphere decreased further, whereas in patients whose motor function remained poor, abnormal inhibition in the unaffected hemisphere persisted. No modification of F-wave latency and amplitude were found in patients and controls. Conclusions. During early days after stroke, motor cortical disinhibition involves both cerebral hemispheres. Longitudinal changes in motor disinhibition of the unaffected hemisphere may reflect the degree of clinical motor recovery.

Clinical efficacy of two toothbrushes with different bristles

The purpose of this single-blind clinical study was to evaluate the efficacy of an innovative manual toothbrush versus a traditional one. The toothbrushes were randomly assigned to 30 volunteers in a student population of the Dental School of the University of Bologna, Italy, divided into 15 test and 15 control subjects. A clinical examination assessing Plaque Index (PI), Gingival Index (GI) and buccal Gingival Recessions was performed at baseline, 3 and 6 months. During the baseline examination, each subject received dental debridement, oral hygiene instructions and a standard kit containing: three standard tubes of toothpaste, 1 hourglass (2 min) and one plaque disclosing solution; each subject of the test group received three innovative toothbrushes, while each subject of the control group received three traditional toothbrushes. During the 6 months of observation both groups presented a PI and GI decrease. A more evident improvement of both indices was observed in the test group (PI P = 0.0001, GI P = 0.0001). The greatest part of recessions remained stable (0-3 months: 70% test group, 60% control group and 3-6 months: 86% test group, 94% control group). Some amplitude modifications (0.5 mm) were mainly detected in the first 3 months (control group chi(2) = 17.55, P = 0.0001 and test group chi(2) = 3.31, P = 0.07). They always increased in the control group and decreased in the study group. The innovative manual toothbrush is more likely to be effective in reducing PI and GI compared to the traditional one and widely safe on periodontal tissues during the period of observation.

Is there still a [formula omitted] puzzle?

We perform a fit to the 2006 B → π K data and show that, when one includes (reasonable) theoretical input, there is a disagreement with the Standard Model. That is, the B → π K puzzle is still present. In fact, it has gotten worse than in earlier years. Assuming that one new-physics (NP) operator dominates, we show that a good fit is obtained only when one type of NP is added (this includes a modification of the electroweak penguin amplitude). The NP amplitude must be sizeable, with a large weak phase.

Abnormalities of the contingent negative variation in Huntington's disease: Correlations with clinical features

The contingent negative variation (CNV) is a neurophysiological pattern related to planning of external — paced, voluntary movements. The aim of the study, was to examine the CNV in a cohort of mild demented and non-medicated HD patients, evaluating the CNV amplitude modifications in the light of clinical features and performing Low Resolution Brain Electromagnetic Tomography (LORETA) analysis in order to show the CNV multiple generators. Fourteen HD patients and 25 sex and age-matched controls were studied. All subjects were evaluated by the motor section of UHDRS, MMSE and WAIS. The CNV was recorded by 19 scalp electrodes, with a red light flash as visual warning stimulus (S1), followed by a blue light flash (S2) after a fixed interval of 3 s. The amplitude of early CNV was significantly reduced in HD, compared to controls: the amplitude reduction was significantly correlated with the bradikinesia score. LORETA analysis of early CNV significantly discriminated patients from controls, for a prevalent activation of the posterior part of anterior cingulate cortex in HD. An abnormal activation of the associative cortex devoted to the processing of attention preceding voluntary movement may be supposed in HD, probably mediated by the altered basal ganglia modulation.

An [formula omitted] KvBLL caloron gas model and confinement

A semi-classical model is developed to describe pure SU ( 2 ) Yang–Mills gluodynamics at finite temperature as a dilute, non-interacting gas of Kraan–van Baal–Lee–Lu calorons including the case of non-trivial holonomy. Temperature-dependent parameters of the model (asymptotic caloron holonomy, caloron density and caloron size distribution) are discussed from the point of view of lattice observations and of in-medium modifications of the one-loop caloron amplitude. Space-like string tensions running into plateaux at distances R ≈ 0.8 – 1.3 fm are obtained and compared to lattice results in order to find more precisely the average caloron size. Then, the quark–antiquark free energy as predicted by the model is considered. In the confined phase a linear rise with the separation can be observed up to R ≈ 4 fm , whereas it runs into plateaux above T c . Screening effects in the adjoint potentials are observed together with an approximate Casimir scaling of the caloron contribution to the fundamental and adjoint forces. In Abelian projection, space-like percolation of monopoles is found in the confined phase only. Thus, taking the non-trivial holonomy into account, confinement properties of pure SU ( 2 ) Yang–Mills gluodynamics can be described by a semi-classical approach up to distances one order of magnitude larger than the caloron size.

Analysis of D/A and A/D Conversions in Quantization-based Audio Watermarking

Due to its advantages, quantization-based embedding has been introduced into audio watermarking to improve robustness performance. Existing audio watermarking algorithms often focus on a given attack. However, in some transmission environments, digital audio files may suffer from the different attacks. For example, effects of D/A and A/D conversions (denoted as DA/AD in this paper) on audio watermarking may be modeled as modification of signal energy, phase changes, and noises corruption. These effects present an important challenge to audio watermarking. Extensive experiments show that phase changes of audio signals caused by the DA/AD may be represented as some extent of temporal scaling. Furthermore, we analyze the performance of quantization-based audio watermarking against these attacks in the DA/AD, and present corresponding calculation expressions of BER (Bit Error Rate) in case of Gaussian noise and modification of audio amplitude, and then investigate the influences of temporal scaling caused by the DA/AD on audio watermarking. As a conclusion, audio watermarking quantization-based is very susceptible to the DA/AD.

Control of Li2 wave packet dynamics by modification of the quantum mechanical amplitude of a single state

Sequences of pulses with different spectra are used to control rotational wave packet dynamics in Li(2) by exploiting quantum interference phenomena. Wave packet superpositions are excited in a two-step resonant Raman process by two different pulses. Interferences between individual states shared by both wave packets can be used to enhance or destroy specific components of a superposition by varying the time delay between the pulses and/or the relative phase within the pulses. Elimination of selected quantum beats is achieved by greater than 94% for each case. A simple, yet effective, method for generating different color phase-locked pairs of laser pulses in a liquid-crystal pulse shaper setup without the need for interferometric stabilization schemes is described. The ability to manipulate single states of a superposition is an important advancement for intuitive control schemes and provides a potential new approach for initialization schemes in the field of quantum information.