Multipeaked Waves Research Articles

Multi-soliton interactions, comb behavior, strange mixed breathers and other exotic rogue waves generated in a nonlinear left-handed transmission line

We establish a cubic–quintic-nonlinear Schrödinger equation (CQNLSE) including cubic- and quintic-nonlinearities, second-, third- and fourth-order dispersions in a left-handed nonlinear transmission line. We use the collective coordinates’ theory and the Gaussian Ansatz function with six coordinates to improve the comprehension of the system. Besides, the following innovations have been found when linear and nonlinear effects interact. (i) Some phenomena have emerged such as comb behavior, fragmentation of waves and wall of waves. (ii) Some solutions have also emerged such as the dark soliton, multi-peak waves, Kuznetsov–Ma breathers, periodical and non periodical mixed wave trains, Sasa–Satsuma waves, Peregrine waves, and crossed solitons. Otherwise, the internal perturbations leading to all aforementioned exotic rogue events are well studied in detail.

Development of Empirical Formulas for Approximate Spectral Moment Based on Rain-Flow Counting Stress-Range Distribution

Many studies have been performed to predict a reliable and accurate stress-range distribution and fatigue damage regarding the Gaussian wide-band stress response due to multi-peak waves and multiple dynamic loads. So far, most of the approximation models provide slightly inaccurate results in comparison with the rain-flow counting method as an exact solution. A step-by-step study was carried out to develop new approximate spectral moments that are close to the rain-flow counting moment, which can be used for the development of a fatigue damage model. Using the special parameters and bandwidth parameters, four kinds of parameter-based combinations were constructed and estimated using the R-squared values from regression analysis. Based on the results, four candidate empirical formulas were determined and compared with the rain-flow counting moment, probability density function, and root mean square (RMS) value for relative distance. The new approximate spectral moments were finally decided through comparison studies of eight response spectra. The new spectral moments presented in this study could play an important role in improving the accuracy of fatigue damage model development. The present study shows that the new approximate moment is a very important variable for the enhancement of Gaussian wide-band fatigue damage assessment.

Infraslow coordination of slow wave activity through altered neuronal synchrony.

Slow wave activity (SWA; the EEG power between 0.5 and 4 Hz during non-rapid eye movement sleep [NREM]) is the best electrophysiological marker of sleep need; SWA dissipates across the night and increases following sleep deprivation. In addition to these well-documented homeostatic SWA trends, SWA exhibits extensive variability across shorter timescales (seconds to minutes) and between local cortical regions. The physiological underpinnings of SWA variability, however, remain poorly characterized. In male Sprague-Dawley rats, we observed that SWA exhibits pronounced infraslow fluctuations (~40- to 120-s periods) that are coordinated across disparate cortical locations. Peaks in SWA across infraslow cycles were associated with increased slope, amplitude, and duration of individual slow waves and a reduction in the total number of waves and proportion of multipeak waves. Using a freely available data set comprised of extracellular unit recordings during consolidated NREM episodes in male Long-Evans rats, we further show that infraslow SWA does not appear to arise as a consequence of firing rate modulation of putative excitatory or inhibitory neurons. Instead, infraslow SWA was associated with alterations in neuronal synchrony surrounding "On"/"Off" periods and changes in the number and duration of "Off" periods. Collectively, these data provide a mechanism by which SWA can be coordinated across disparate cortical locations and thereby connect local and global expression of this patterned neuronal activity. In doing so, infraslow SWA may contribute to the regulation of cortical circuits during sleep and thereby play a critical role in sleep function.

Traveling wave solutions of a highly nonlinear shallow water equation

Motivated by the question whether higher-order nonlinear model equations, which go beyond the Camassa-Holm regime of moderate amplitude waves, could point us to new types of waves profiles, we study the traveling wave solutions of a quasilinear evolution equation which models the propagation of shallow water waves of large amplitude. The aim of this paper is a complete classification of its traveling wave solutions. Apart from symmetric smooth, peaked and cusped solitary and periodic traveling waves, whose existence is well-known for moderate amplitude equations like Camassa-Holm, we obtain entirely new types of singular traveling waves: periodic waves which exhibit singularities on both crests and troughs simultaneously, waves with asymmetric peaks, as well as multi-crested smooth and multi-peaked waves with decay. Our approach uses qualitative tools for dynamical systems and methods for integrable planar systems.

Differences in electroencephalographic non-rapid-eye movement sleep slow-wave characteristics between young and old mice

Changes in sleep pattern are typical for the normal aging process. However, aged mice show an increase in the amount of sleep, whereas humans show a decrease when aging. Mice are considered an important model in aging studies, and this divergence warrants further investigation. Recently, insights into the network dynamics of cortical activity during sleep were obtained by investigating characteristics of individual electroencephalogram (EEG) slow waves in young and elderly humans. In this study, we investigated, for the first time, the parameters of EEG slow waves, including their incidence, amplitude, duration and slopes, in young (6 months) and older (18–24 months) C57BL/6J mice during undisturbed 24 h, and after a 6-h sleep deprivation (SD). As expected, older mice slept more but, in contrast to humans, absolute NREM sleep EEG slow-wave activity (SWA, spectral power density between 0.5–4 Hz) was higher in the older mice, as compared to the young controls. Furthermore, slow waves in the older mice were characterized by increased amplitude, steeper slopes and fewer multipeak waves, indicating increased synchronization of cortical neurons in aging, opposite to what was found in humans. Our results suggest that older mice, in contrast to elderly humans, live under a high sleep pressure.

Genesis of multipeaked waves of the esophagus: repetitive contractions or motion artifact?

Multipeaked waves (MPW) in the distal esophagus occur frequently in patients with esophageal spastic motor disorders and diabetes mellitus and are thought to represent repetitive esophageal contractions. We aimed to investigate whether the relative motion between a stationary pressure sensor and contracted peristaltic esophageal segment that moves with respiration leads to the formation of MPW. We mathematically modeled the effect of relative movement between a moving pressure segment and a fixed pressure sensor on the pressure waveform morphology. We conducted retrospective analysis of 100 swallow-induced esophageal contractions in 10 patients, who demonstrated >30% MPW on high-resolution manometry (HRM) during standardized swallows. Finally, using HRM, we determined the effects of suspended breathing and hyperventilation on the waveform morphology in 10 patients prospectively. Modeling revealed that relative movement between a stationary pressure sensor and a moving contracted segment, contraction duration, contraction amplitude, respiratory frequency, and depth of respiration affects the waveform morphology. Retrospective analysis demonstrated a close temporal association with the onset of second and subsequent contractions in MPW with respiratory phase reversals. Numbers of peaks in MPW and respiratory phase reversals were closely related to the duration of contraction. In the prospective study, suspended breathing and hyperventilation resulted in a significant decrease and increase in the MPW frequency as well as the number of peaks within MPW respectively. We conclude that MPW observed during clinical motility studies are not indicative of repetitive esophageal contraction; rather they represent respiration-related movement of the contracted esophageal segment in relation to the stationary pressure sensor.

Slow oscillations in human non-rapid eye movement sleep electroencephalogram: effects of increased sleep pressure

Slow oscillations (< 1 Hz) in the non-rapid eye movement (NREM) sleep electroencephalogram (EEG) result from slow membrane potential fluctuations of cortical neurones, alternating between a depolarized up-state and a hyperpolarized down-state. They are thought to underlie the restorative function of sleep. We investigated the behaviour of slow oscillations in humans under increased sleep pressure to assess their contribution to sleep homeostasis. EEG recordings (C3A2) of baseline and recovery sleep after sleep deprivation (eight healthy males, mean age 23 years; 40 h of prolonged wakefulness) were analysed. Half-waves were defined as positive or negative deflections between consecutive zero crossings in the 0.5-2 Hz range of the band-pass filtered EEG. Increased sleep pressure resulted in a redistribution of half-waves between 0.5 and 2 Hz: the number of half-waves per minute was reduced below 0.9 Hz while it was increased above 1.2 Hz. EEG power was increased above 1 Hz. The increase in frequency was accompanied by increased slope of the half-waves and decreased number of multi-peak waves. In both baseline and recovery sleep, amplitude and slope were correlated highly over a broad frequency range and positive half-waves were characterized by a lower frequency than the negative ones, pointing to a longer duration of up- than down-states. We hypothesize that the higher frequency of slow oscillatory activity after prolonged wakefulness may relate to faster alternations between up- and down-states at the cellular level under increased sleep pressure. This study does not question slow-wave activity as a marker of sleep homeostasis, as the observed changes occurred within the same frequency range.

T1226 Genesis of Multi-Peaked Waves of the Esophagus: Repetitive Contractions or Motion Artifact?

Sampath NJ, Bhargava V, Mittal RK. Genesis of multipeaked waves of the esophagus: repetitive contractions or motion artifact?. Am J Physiol Gastrointest Liver Physiol 298: G927–G933, 2010. First published April 1, 2010; doi:10.1152/ajpgi.00044.2010.—Multipeaked waves (MPW) in the distal esophagus occur frequently in patients with esophageal spastic motor disorders and diabetes mellitus and are thought to represent repetitive esophageal contractions. We aimed to investigate whether the relative motion between a stationary pressure sensor and contracted peristaltic esophageal segment that moves with respiration leads to the formation of MPW. We mathematically modeled the effect of relative movement between a moving pressure segment and a fixed pressure sensor on the pressure waveform morphology. We conducted retrospective analysis of 100 swallow-induced esophageal contractions in 10 patients, who demonstrated 30% MPW on high-resolution manometry (HRM) during standardized swallows. Finally, using HRM, we determined the effects of suspended breathing and hyperventilation on the waveform morphology in 10 patients prospectively. Modeling revealed that relative movement between a stationary pressure sensor and a moving contracted segment, contraction duration, contraction amplitude, respiratory frequency, and depth of respiration affects the waveform morphology. Retrospective analysis demonstrated a close temporal association with the onset of second and subsequent contractions in MPW with respiratory phase reversals. Numbers of peaks in MPW and respiratory phase reversals were closely related to the duration of contraction. In the prospective study, suspended breathing and hyperventilation resulted in a significant decrease and increase in the MPW frequency as well as the number of peaks within MPW respectively. We conclude that MPW observed during clinical motility studies are not indicative of repetitive esophageal contraction; rather they represent respiration-related movement of the contracted esophageal segment in relation to the stationary pressure sensor.

Sleep Homeostasis and Cortical Synchronization: III. A High-Density EEG Study of Sleep Slow Waves in Humans

The mechanisms responsible for the homeostatic decrease of slow-wave activity (SWA, defined in this study as electroencephalogram [EEG] power between 0.5 and 4.0 Hz) during sleep are unknown. In agreement with a recent hypothesis, in the first of 3 companion papers, large-scale computer simulations of the sleeping thalamocortical system showed that a decrease in cortical synaptic strength is sufficient to account for the decline in SWA. In the model, the reduction in SWA was accompanied by decreased incidence of high-amplitude slow waves, decreased wave slopes, and increased number of waves with multiple peaks. In a second companion paper in the rat, local field potential recordings during early and late sleep confirmed the predictions of the model. Here, we investigated the model's predictions in humans by using all-night high-density (hd)-EEG recordings to explore slow-wave parameters over the entire cortical mantle. 256-channel EEG recordings in humans over the course of an entire night's sleep. Sound-attenuated sleep research room Seven healthy male subjects N/A. During late sleep (non-rapid eye movement [NREM] episodes 3 and 4, toward morning), when compared with early sleep (NREM sleep episodes 1 and 2, at the beginning of the night), the analysis revealed (1) reduced SWA, (2) fewer large-amplitude slow waves, (3) decreased wave slopes, (4) more frequent multipeak waves. The decrease in slope between early and late sleep was present even when waves were directly matched by wave amplitude and slow-wave power in the background EEG. Finally, hd-EEG showed that multipeak waves have multiple cortical origins. In the human EEG, the decline of SWA during sleep is accompanied by changes in slow-wave parameters that were predicted by a computer model simulating a homeostatic reduction of cortical synaptic strength.

Sleep Homeostasis and Cortical Synchronization: II. A Local Field Potential Study of Sleep Slow Waves in the Rat

Sleep slow-wave activity (SWA, EEG power between 0.5 and 4.0 Hz) decreases homeostatically in the course of non-rapid eye movement sleep (NREM) sleep. According to a recent hypothesis, the homeostatic decrease of sleep SWA is due to a progressive decrease in the strength of corticocortical connections. This hypothesis was evaluated in a large-scale thalamocortical model, which showed that a decrease in synaptic strength, implemented through a reduction of postsynaptic currents, resulted in lower sleep SWA in simulated local field potentials (LFP). The decrease in SWA was associated with a decreased proportion of high-amplitude slow waves, a decreased slope of the slow waves, and an increase in the number of multipeak waves. Here we tested the model predictions by obtaining LFP recordings from the rat cerebral cortex and comparing conditions of high homeostatic sleep pressure (early sleep) and low homeostatic sleep pressure (late sleep). Intracortical LFP recordings during baseline sleep and after 6 hours of sleep deprivation. Basic sleep research laboratory. WKY adult male rats. N/A. Early sleep (sleep at the beginning of the major sleep phase, sleep immediately after sleep deprivation) was associated with (1) high SWA, (2) many large slow waves, (3) steep slope of slow waves, and (4) rare occurrence of multipeak waves. By contrast, late sleep (sleep at the end of the major sleep phase, sleep several hours after the end of sleep deprivation) was associated with (1) low SWA, (2) few high-amplitude slow waves, (3) reduced slope of slow waves, and (4) more frequent multipeak waves. In rats, changes in sleep SWA are associated with changes in the amplitude and slope of slow waves, and in the number of multi-peak waves. Such changes in slow-wave parameters are compatible with the hypothesis that average synaptic strength decreases in the course of sleep.

Sleep Homeostasis and Cortical Synchronization: I. Modeling the Effects of Synaptic Strength on Sleep Slow Waves

Sleep slow-wave activity (SWA, electroencephalogram [EEG] power between 0.5 and 4.0 Hz) is homeostatically regulated, increasing with wakefulness and declining with sleep. Sleep SWA is thought to reflect sleep need, but the mechanisms of its homeostatic regulation remain unknown. Based on a recent hypothesis, we sought to determine whether a decrease in cortical synaptic strength can account for changes in sleep SWA. A large-scale computer model of the sleeping thalamocortical system was used to reproduce in detail the cortical slow oscillations underlying EEG slow waves. N/A. N/A. Simulated reductions in the strength of corticocortical synapses. Decreased synaptic strength led to (1) decreased single cell membrane potential oscillations and reduced network synchronization, (2) decreased rate of neural recruitment and decruitment, and (3) emergence of local clusters of synchronized activity. These changes were reflected in the local EEG as (1) decreased incidence of high-amplitude slow waves, (2) decreased wave slope, and (3) increased number of multipeak waves. Spectral analysis confirmed that these changes were associated with a decrease in SWA. A decrease in cortical synaptic strength is sufficient to account for changes in sleep SWA and is accompanied by characteristic changes in slow-wave parameters. Experimental results from rat cortical depth recordings and human high-density EEG show similar changes in slow-wave parameters with decreasing SWA, suggesting that the underlying mechanism may indeed be a net decrease in synaptic strength.

Ceramic superconducting materials as intercalation cathodes in secondary non-aqueous lithium batteries

Electrodes formed from PTFE bound (Ta 1/2Cu 1/2) Sr 2GdCu 2O 8 − d , were cycled in 1 M LiAsF 6/propylene carbonate electrolyte using cyclic voltammetry. It has been demonstrated that the cyclic voltammograms measured below 2.0 mV s −1 exhibit a well defined reversible multipeaked wave. Prototype cells incorporating both PTFE bound and thin highly porous films of (Ta 1/2Cu 1/2)Sr 2GdCu 2O 8 − d exhibited an initial discharge with two well defined voltage steps. Subsequent discharge cycles only retain characteristics of the higher voltage step suggesting that the process characterised by the low voltage step is irreversible.

Physiologic assessment and surgical management of diffuse esophageal spasm

The physiologic abnormalities and management of patients with diffuse esophageal spasm are controversial. We evaluated the symptomatic and functional results of surgical therapy in 19 patients with diffuse esophageal spasm who were incapacitated with dysphagia and chest pain and unresponsive to conservative management. A long esophageal myotomy with an antireflux procedure was performed in 15 patients, and four patients with multiple previous esophageal procedures had an esophagectomy. Eleven patients had increased esophageal exposure to gastric juice on preoperative 24-hour esophageal pH monitoring. The severity of dysphagia, chest pain, regurgitation, and heartburn was scored on a scale of 0 to 3 before and a mean of 24 months (range 8 months to 13 years) after the operation. After myotomy, each of these symptoms and the overall symptom score improved significantly (p < 0.01). The improvement in the symptom scores in the patients who had esophagectomy were comparable with the improvement after myotomy. On self-assessment, 90% of the patients would have the operation again if again faced with the decision. Standard and ambulatory 24-hour manometry showed a significant reduction in the amplitude of the esophageal body contractions, a decrease in the frequency of simultaneous contractions, and the elimination of multi-peaked waves after the myotomy. Despite the addition of an antireflux procedure, lower esophageal sphincter pressure, overall length, and abdominal length were reduced markedly after the myotomy. This was associated with persistent or emerging heartburn or regurgitation in four patients. These data indicate that a long esophageal myotomy is a valid treatment alternative in appropriately selected patients with diffuse esophageal spasm. Esophagectomy and colon interposition is the procedure of choice in patients with multiple previously failed myotomies.

Clinical correlates of abnormal sensitivity to intraesophageal balloon distension

Sixty-five patients with esophageal complaints were studied to determine clinical associations with abnormal sensitivity to intraesophageal balloon distension (esophageal sensory dysfunction). Associations were examined in four categories: motility, esophageal symptoms, recent psychological symptoms, and general clinical features. A positive response to balloon distension (pain with less than or equal to 8 ml volume) was found in 29 (45%) of the subjects. This response was associated with specific findings in each category except recent psychological symptoms. A multiple logistic regression analysis indicated that an increased frequency of multipeaked waves on motility testing, presence of dysphagia, and shorter height of the subject each had an independent association with positive response to balloon distension (P less than or equal to 0.05 for each). Further comparison of subjects with sensory dysfunction, motor dysfunction, or both (sensorimotor dysfunction) indicated that subjects with the combined disorder appeared more symptomatic than those with either finding alone. These observations indicate that: (1) esophageal motor and sensory dysfunction are partially associated, but both contribute to the symptomatic state; (2) dysphagia may be representative of sensory dysfunction in some cases; and (3) subject height should be taken into consideration when interpreting balloon distension results.