Wave Slope Research Articles

Long-term history and immediate preceding state affect EEG slow wave characteristics at NREM sleep onset in C57BL/6 mice.

The dynamics of cortical activity across the 24-h day and at vigilance state transitions is regulated by an interaction between global subcortical neuromodulatory influences and local shifts in network synchrony and excitability. To address the role of long-term and immediate preceding history in local and global cortical dynamics, we investigated cortical EEG recorded from both frontal and occipital regions during an undisturbed 24-h recording in mice. As expected, at the beginning of the light period, under physiologically increased sleep pressure, EEG slow waves were more frequent and had higher amplitude and slopes, compared to the rest of the light period. Within discrete NREM sleep episodes, the incidence, amplitude and slopes of individual slow waves increased progressively after episode onset in both derivations by approximately 10-30%. Interestingly, at the beginning of NREM sleep episodes slow waves in the frontal and occipital derivations frequently occurred in isolation, as quantified by longer latencies between consecutive slow waves in the two regions. Notably, slow waves during the initial period of NREM sleep following REM sleep episodes were significantly less frequent, lower in amplitude and exhibited shallower slopes, compared to those that occurred in NREM episodes after prolonged waking. Moreover, the latencies between consecutive frontal and occipital NREM slow waves were substantially longer when they occurred directly after REM sleep compared to following consolidated wakefulness. Overall these data reveal a complex picture, where both time of day and preceding state contribute to the characteristics and dynamics of slow waves within NREM sleep. These findings suggest that NREM sleep initiates in a more "local" fashion when it occurs following REM sleep episodes as opposed to sustained waking bouts. While the mechanisms and functional significance of such a re-setting of brain state after individual REM sleep episodes remains to be investigated, we suggest that it may be an essential feature of physiological sleep regulation.

Long-term history and immediate preceding state affect EEG slow wave characteristics at NREM sleep onset in C57BL/6 mice

The dynamics of cortical activity across the 24-h day and at vigilance state transitions is regulated by an interac- tion between global subcortical neuromodulatory influences and local shifts in network synchrony and excitability. To address the role of long-term and immediate preceding history in local and global cortical dynamics, we inves- tigated cortical EEG recorded from both frontal and occipital regions during an undisturbed 24-h recording in mice. As expected, at the beginning of the light period, under physiologically increased sleep pressure, EEG slow waves were more frequent and had higher amplitude and slopes, compared to the rest of the light period. Within discrete NREM sleep episodes, the incidence, amplitude and slopes of individual slow waves increased progres- sively after episode onset in both derivations by approximately 10-30%. Interestingly, at the beginning of NREM sleep episodes slow waves in the frontal and occipital derivations frequently occurred in isolation, as quantified by longer latencies between consecutive slow waves in the two regions. Notably, slow waves during the initial period of NREM sleep following REM sleep episodes were significantly less frequent, lower in amplitude and exhibited shallower slopes, compared to those that occurred in NREM episodes after prolonged waking. Moreover, the laten- cies between consecutive frontal and occipital NREM slow waves were substantially longer when they occurred directly after REM sleep compared to following consolidated wakefulness. Overall these data reveal a complex picture, where both time of day and preceding state contribute to the characteristics and dynamics of slow waves within NREM sleep. These findings suggest that NREM sleep initiates in a more “local” fashion when it occurs following REM sleep episodes as opposed to sustained waking bouts. While the mechanisms and functional signifi- cance of such a re-setting of brain state after individual REM sleep episodes remains to be investigated, we suggest that it may be an essential feature of physiological sleep regulation.

Long-term history and immediate preceding state affect EEG slow wave characteristics at NREM sleep onset in C57BL/6 mice

The dynamics of cortical activity across the 24-h day and at vigilance state transitions is regulated by an interac- tion between global subcortical neuromodulatory influences and local shifts in network synchrony and excitability. To address the role of long-term and immediate preceding history in local and global cortical dynamics, we inves- tigated cortical EEG recorded from both frontal and occipital regions during an undisturbed 24-h recording in mice. As expected, at the beginning of the light period, under physiologically increased sleep pressure, EEG slow waves were more frequent and had higher amplitude and slopes, compared to the rest of the light period. Within discrete NREM sleep episodes, the incidence, amplitude and slopes of individual slow waves increased progres- sively after episode onset in both derivations by approximately 10-30%. Interestingly, at the beginning of NREM sleep episodes slow waves in the frontal and occipital derivations frequently occurred in isolation, as quantified by longer latencies between consecutive slow waves in the two regions. Notably, slow waves during the initial period of NREM sleep following REM sleep episodes were significantly less frequent, lower in amplitude and exhibited shallower slopes, compared to those that occurred in NREM episodes after prolonged waking. Moreover, the laten- cies between consecutive frontal and occipital NREM slow waves were substantially longer when they occurred directly after REM sleep compared to following consolidated wakefulness. Overall these data reveal a complex picture, where both time of day and preceding state contribute to the characteristics and dynamics of slow waves within NREM sleep. These findings suggest that NREM sleep initiates in a more “local” fashion when it occurs following REM sleep episodes as opposed to sustained waking bouts. While the mechanisms and functional signifi- cance of such a re-setting of brain state after individual REM sleep episodes remains to be investigated, we suggest that it may be an essential feature of physiological sleep regulation.

Changes in heart rate variability and pulse wave characteristics during normal pregnancy and postpartum

In the present study, the ongoing maternal haemodynamic and cardiovascular changes during pregnancy and postpartum stage have been studied using pulse waveform analysis. The ECG and pulse are simultaneously recorded from the subjects in the first trimester, second trimester, third trimester pregnant women and postpartum. The heart rate variability (HRV) and the pulse characteristics such as pulse rate interval (PR), peak to peak amplitude (PP), rise time (T1), width (W), slope (dV/dt) of the percussion wave are measured and pulse transit time (PTT) in each cardiac cycle is computed. The analysis shows that mean PR, PP, T1, slope, W and PTT are statistically significant differences during pregnancy compared to the postpartum stage. The results suggest that pulse parameters can be used for quantification of sympathetic and parasympathetic activities and the haemodynamic changes during pregnancy.

津波入射波の形状が橋梁上部構造に作用する津波波力に及ぼす影響

In the Tohoku-Pacific Ocean Earthquake, many bridges were washed away by the tsunami. In the future, countermeasure for tsunami disaster will be needed, and the evaluation of tsunami wave force acting on bridges will be very important. This paper discusses the hydrodynamic tsunami-induced force acting on a bridge superstructure based on hydraulic model experiments. The results showed that tsunami wave forces were different according to the shape of tsunami incident wave and it was confirmed that maximum wave forces could be expressed by a function of the wave front slope of tsunami incident wave.

Retrieval of Higher Order Ocean Spectral Information From Sunglint

An approach was developed to retrieve the ocean slope bispectrum, which describes the nonlinearity of the slope surface, from ocean sunglint data. The departure from Gaussianity of the ocean slope was described using an N-dimensional slope joint probability density function, which was derived using a perturbative approach. The resulting Edge-worth series had various slope cumulants and cumulant functions as series coefficients, and multidimensional Hermite polynomials as the series basis functions. The slope probability density was used to specify a series of relationships between the slope and glint cumulants and cumulant functions up to third order. These relationships were inverted to retrieve the slope third cumulant function, from which we obtained the slope bispectrum via Fourier transformation. The retrieval method was validated using synthetic 1-D ocean wave slope datasets with controlled phase correlations imposed on a subset of the wave spectrum components.

A note on the onset of recirculation in a 2D Couette flow over a wavy bottom

Laminar Couette flow over a fixed wavy surface was studied with direct numerical simulation in a 2D periodic numerical domain. The mesh was generated by a conformal transformation that sets horizontal flow at the top of the domain, where a constant velocity boundary condition is given. The bottom of the domain is a wavy sinusoidal surface of wave slope 2πa/λ. The combined effect of bottom shape, inertia, and viscosity was explored using different Reynolds numbers (Re) and two dimensionless parameters in terms of channel width h, wavelength λ, and the amplitude of the wavy bottom a. Even if the Reynolds number was large, the simulations were not perturbed so the regime was always laminar. However, a recirculation appeared at the vicinity of the trough. The horizontal location of the eddy center was reported as a function of 2πa/λ and Reλ/h. The conditions for the onset of this recirculation were studied and compared with results from the literature. Two regimes can be clearly identified from the numerical results; a viscous regime with a weak dependence between 2πa/λ and Reλ/h for small Reynolds numbers and an inertial regime with an exponential dependence between 2πa/λ and Reλ/h for large Reynolds numbers, which presents an approximate slope of −1/3. Almost all results collapse in one single curve that characterizes the phenomenon (with the exception of some points where the flow is confined due to a large λ/h ratio).

Viscous drift current on the slopes of wind waves at the onset of acceleration

A technique for calculating viscous drift on the slopes of waves in the zone of their generation is proposed. Viscous stress is calculated for the wave’s front slope and the water-air interface. The calculations are performed with allowance for the eddies that form in the expanding viscous layer of wind flow and the deforming of the water’s surface. The technique is validated on the basis of experimental data.

Run-up of non-breaking double solitary waves with equal wave heights on a plane beach

The evolution and run-up of double solitary waves on a plane beach were studied numerically using the nonlinear shallow water equations (NSWEs) and the Godunov scheme. The numerical model was validated through comparing the present numerical results with analytical solutions and laboratory measurements available for propagation and run-up of single solitary wave. Two successive solitary waves with equal wave heights and variable separation distance of two crests were used as the incoming wave on the open boundary at the toe of a slope beach. The run-ups of the first wave and the second wave with different separation distances were investigated. It is found that the run-up of the first wave does not change with the separation distance and the run-up of the second wave is affected slightly by the separation distance when the separation distance is gradually shortening. The ratio of the maximum run-up of the second wave to one of the first wave is related to the separation distance as well as wave height and slope. The run-ups of double solitary waves were compared with the linearly superposed results of two individual solitary-wave run-ups. The comparison reveals that linear superposition gives reasonable prediction when the separation distance is large, but it may overestimate the actual run-up when two waves are close.

Impaired slow wave sleep downscaling in patients with infantile spasms

BackgroundWest syndrome is a severe epileptic encephalopathy of infancy, characterized by infantile spasms, global retardation, and a severely abnormal electroencephalogram (EEG) pattern known as hypsarrhythmia, which is most prominent during slow waves sleep. The restorative function of slow wave sleep has been linked to downscaling, a neuronal process ensuring a balance of global synaptic strength, which is important for normal cortical functioning and development. A key electrophysiological marker for this downscaling is the reduction of the slope of slow waves across the night. MethodsWe retrospectively compared the slope of slow waves between 14 untreated patients with infantile spasms and healthy age and gender matched controls. Patients were examined in one all-night sleep EEG before treatment, and in two follow-up nap recordings, under and after treatment with corticosteroids. ResultsIn patients with infantile spasms the overnight reduction in the slope of slow waves was significantly diminished compared to controls (p = 0.009). Moreover, untreated patients revealed overall steeper slopes. During corticosteroid treatment the slope was reduced compared to controls (p = 0.001). After successful treatment the slope was similar between patients and controls. ConclusionOur results provide evidence for reduced downscaling in patients with infantile spasms. Moreover, the marked reduction of the slope during corticosteroid treatment may reflect a loss of synaptic connections due to the effect of glucocorticoids. This altered sleep dependent regulation of synaptic strength in infantile spasms may contribute the underlying pathomechanism of the developmental regression. Furthermore the normalization of synaptic strength due to corticosteroids might provide a potential mechanistic explanation for this treatment strategy.

Abstract 12589: Quantitative Assessment of Mid-Systolic Deceleration and Notching in the Right Ventricular Ejection Doppler Envelope is Useful in Predicting Hemodynamics and Patient Outcomes in Pulmonary Arterial Hypertension

Background: Increased reflective wave from pulmonary artery (PA) causes mid-systolic deceleration (MSD) and notching in Doppler flow velocity envelope of RV ejection flow. Our aim is to test whether profile of MSD and notching provides insight into hemodynamics and patient outcomes in pulmonary artery hypertension (PAH), using quantitative measurements. We hypothesized that the deceleration time of the MSD slope (DTMSD), meaning the steepness of the slope, reflects interaction between RV ejection and reflective wave, and that peak velocity of post-notching flow (Vpost) reflects RV function. Methods: We reviewed RV ejection flow envelope recordings by pulsed wave Doppler for 157 consecutive patients with PAH between 1/2008 and 3/2013 (age 57 ± 14) with an estimated RV systolic pressure of 79 ± 23 mmHg. DTMSD was measured as the time between the first peak acceleration wave and MSD slope extrapolated to zero line. We also reviewed right heart catheterization performed within one month from echocardiography in 78 of the 157 patients. Results: We identified MSD and notching in 148 patients. On multivariate regression analyses, PA capacitance was the key determinant of DTMSD (beta = -0.49, p <0.0001). Vpost was determined by cardiac index (beta = -0.36, p = 0.0014). During a median follow-up period of 30 months, there were 47 deaths from all causes and 7 lung transplantations. On Cox hazard analyses, shorter DTMSD and smaller Vpost are significant predictors of higher mortality independently of each other (HR 0.92 / 10ms, p = 0.045 and HR 0.97, p = 0.028, respectively). Conclusion: Mid-systolic deceleration of RV ejection flow became steeper in the setting of lower PA compliance causing a greater reflectance wave. Reduced peak velocity of post-notching flow reflected impaired RV with reduced cardiac output. Quantitative assessment of profile of mid-systolic deceleration and notching in RV ejection flow envelope is useful in predicting hemodynamics and patient outcomes in PAH.

Monitoring cardiovascular changes due to local anesthesia during and after tooth extraction using pulse wave analysis

A study was conducted to determine the ongoing short-term changes in pulse waveform and pulse transit time in patients during tooth extraction. The sympathetic stimulation produced during tooth extraction under local anesthesia (LA) utilizing 2% lignocaine with adrenaline is evaluated. The increase in pulse rate due to vasoconstriction in the peripheral blood vessels has been quantifying the sympathetic stimulation to the local anesthesia. The ECG and pulse signals were recorded from 16 non-medically compromised dental patients in resting condition (before local anesthesia), 2–3min after injection of local anesthesia and 5–10min after tooth extraction. The amplitudes and timings of pulse, width, slope, pulse rate interval and PTT were computed for every pulse. More than 25% increase in amplitude and slope of the forward wave and about 15% decrease in rise time and the width of the forward wave were observed after injection of local anesthesia (PostLA) as compared to pre-local anesthesia (PreLA) stages. Indices utilizing the variations on pulse amplitude can provide a window to detect volume of anesthetic and vascular stiffness. It is seen that the PTT decreases more than 5% after LA and increased about 5% after surgery as compared to resting conditions (PreLA). The result suggests that the contour analysis of pulse waveform and PTT can be used to quantify the sympathetic stimulation due to local anesthesia in healthy dental patients. The variations in amplitude shall be given more efforts and attention in order to ride the challenge in developing some means of pulse contour, which can be used to assist in the monitoring of the local anesthetic volume and duration.

Automated J wave detection from digital 12-lead electrocardiogram.

In this report we provide a method for automated detection of J wave, defined as a notch or slur in the descending slope of the terminal positive wave of the QRS complex, using signal processing and functional data analysis techniques. Two different sets of ECG tracings were selected from the EPICARE ECG core laboratory, Wake Forest School of Medicine, Winston Salem, NC. The first set was a training set comprised of 100 ECGs of which 50 ECGs had J-wave and the other 50 did not. The second set was a test set (n=116 ECGs) in which the J-wave status (present/absent) was only known by the ECG Center staff. All ECGs were recorded using GE MAC 1200 (GE Marquette, Milwaukee, Wisconsin) at 10mm/mV calibration, speed of 25mm/s and 500HZ sampling rate. All ECGs were initially inspected visually for technical errors and inadequate quality, and then automatically processed with the GE Marquette 12-SL program 2001 version (GE Marquette, Milwaukee, WI). We excluded ECG tracings with major abnormalities or rhythm disorder. Confirmation of the presence or absence of a J wave was done visually by the ECG Center staff and verified once again by three of the coauthors. There was no disagreement in the identification of the J wave state. The signal processing and functional data analysis techniques applied to the ECGs were conducted at Duke University and the University of Toronto. In the training set, the automated detection had sensitivity of 100% and specificity of 94%. For the test set, sensitivity was 89% and specificity was 86%. In conclusion, test results of the automated method we developed show a good J wave detection accuracy, suggesting possible utility of this approach for defining and detection of other complex ECG waveforms.

Measurement and synthesis of wind turbine infrasound

As part of an ongoing investigation into the putative subjective effects of sub-20 Hz acoustical emissions from large industrial wind turbines, measurement techniques for faithful capture of emissions waveforms have been developed and reported. To evaluate perception thresholds, Fourier synthesis and high fidelity low-frequency playback equipment has been used to duplicate in a residential-like listening environment the amplitudes and wave slopes of the actual emissions, with pulsation rate in the range of 0.5–1.0 per second. Further, the amplitudes and slopes of the synthesized waves can be parametrically varied and the harmonic phases “scrambled” to assess the relative effects on auditory and other subjective responses. Measurement and synthesis system details and initial subjective response results will be shown.

Snell’s window in wavy water

The angular diameter of Snell's window as a function of maximum wave slope is calculated. For flat water the diameter is 97° and increases up to about 122° when the wave slope is about 16°. Steeper waves break and disrupt the smooth surface used in the analysis. Breaking waves produce a window almost 180° wide. The brightness of the dark area around Snell's window is heavily influenced by turbidity and upwelling radiation, especially in shallow water.

Analysis of spatial and temporal evolution of disturbance waves and ripples in annular gas–liquid flow

Wavy structure of liquid film in downward annular gas–liquid flow is studied with high-speed laser-induced fluorescence technique. Film thickness measurements are resolved in both longitudinal distance and time with high spatial and temporal resolution. A method is developed to identify the characteristic lines of individual disturbance waves. Change of frequency of disturbance waves with downstream distance is modelled based on the obtained distributions of the disturbance waves by velocity and separation time. Using obtained characteristic lines further investigation of ripples’ properties is performed in reference system moving with the disturbance wave. As a result, velocities, amplitudes and frequencies of ripples are measured with relation to the distance from disturbance waves. Fast ripples travelling over crests of disturbance waves and slow ripples travelling over back slopes of disturbance waves and over the base film are studied separately. Besides, the average length of crest and back slope of disturbance waves were measured.

Sea wave modelling for motion control applications

The modelling of sea environment is important in designing an effective motion control system for any marine vehicle. Inadequate representation of the components of a typical random sea might lead to poor performance of the control system. A multiple output system such as the one having components of wave elevation and slope, facilitates designing the control system taking into account the different degrees of freedom. The method of modelling the sea environment presented here, provides the basis for the design of motion control systems for multiple degree of freedom cases, which give rise to excitation forces and moments acting on the marine vehicle. The method used here models the sea environment using Gaussian white noise and shaping filter to generate a multiple output form of the random sea state. In the first step a given standard wave spectrum is approximated using a rational polynomial, the coefficients of the polynomial are obtained by least square fitting method to best match the spectrum. The established rational polynomial is then decomposed to get the transfer function of the shaping filter. The wave slope spectrum is similarly approximated using the same rational polynomial. The transfer functions of the two components of amplitude and slope, representing the filters are combined to generate a state space form. Using the white noise as input, the state space form obtains the wave elevation and slope as outputs. By performing spectral analysis using Welch method, the quality of the obtained output is checked against the targetted spectrum. The application of the simulated wave slope spectrum in a closed loop state space model is demonstrated as applied to the roll stabilization characteristics of a stationary ship using a passive tank.DOI: http://dx.doi.org/10.3329/jname.v11i1.17768

Long-term history and immediate preceding state affect EEG slow wave characteristics at NREM sleep onset in C57BL/6 mice.

The dynamics of cortical activity across the 24-h day and at vigilance state transitions is regulated by an interac- tion between global subcortical neuromodulatory influences and local shifts in network synchrony and excitability. To address the role of long-term and immediate preceding history in local and global cortical dynamics, we inves- tigated cortical EEG recorded from both frontal and occipital regions during an undisturbed 24-h recording in mice. As expected, at the beginning of the light period, under physiologically increased sleep pressure, EEG slow waves were more frequent and had higher amplitude and slopes, compared to the rest of the light period. Within discrete NREM sleep episodes, the incidence, amplitude and slopes of individual slow waves increased progres- sively after episode onset in both derivations by approximately 10-30%. Interestingly, at the beginning of NREM sleep episodes slow waves in the frontal and occipital derivations frequently occurred in isolation, as quantified by longer latencies between consecutive slow waves in the two regions. Notably, slow waves during the initial period of NREM sleep following REM sleep episodes were significantly less frequent, lower in amplitude and exhibited shallower slopes, compared to those that occurred in NREM episodes after prolonged waking. Moreover, the laten- cies between consecutive frontal and occipital NREM slow waves were substantially longer when they occurred directly after REM sleep compared to following consolidated wakefulness. Overall these data reveal a complex picture, where both time of day and preceding state contribute to the characteristics and dynamics of slow waves within NREM sleep. These findings suggest that NREM sleep initiates in a more “local” fashion when it occurs following REM sleep episodes as opposed to sustained waking bouts. While the mechanisms and functional signifi- cance of such a re-setting of brain state after individual REM sleep episodes remains to be investigated, we suggest that it may be an essential feature of physiological sleep regulation.

A simple general expression for longshore transport of sand, gravel and shingle

Longshore transport of sand, gravel and shingle has been studied using field and laboratory data over a wide range of conditions. A detailed model (CROSMOR) for cross-shore and longshore sediment transport has been used to determine the effects of wave period, grain size, beach/surf zone slope and type of waves (wind waves or swell waves). The longshore transport was found to be proportional to wave height to the power 3.1 (≈H3.1), to grain size to the power −0.6 (≈d50−0.6) and to beach slope to the power 0.4 (≈tanβ0.4). Regular swell waves yield much larger (factor 1.5) longshore transport rates than irregular wind waves of the same height. It is proposed to take this effect into account by a swell correction factor. Based on all results, a new simple and general (dimensionally correct) expression for longshore transport of sand, gravel and shingle beaches with grain sizes between 0.1 and 100mm has been derived. Short-term and long-term field data of sand, gravel and shingle have been used for verification. In most cases the predicted longshore transport rates are within a factor of 2 of the measured values. The CERC and Kamphuis formulas have also been tested.

Spike wave location and density disturb sleep slow waves in patients with CSWS (continuous spike waves during sleep)

In CSWS (continuous spike waves during sleep) activation of spike waves during slow wave sleep has been causally linked to neuropsychological deficits, but the pathophysiologic mechanisms are still unknown. In healthy subjects, the overnight decrease of the slope of slow waves in NREM (non-rapid eye movement) sleep has been linked to brain recovery to regain optimal cognitive performance. Here, we investigated whether the electrophysiologic hallmark of CSWS, the spike waves during sleep, is related to an alteration in the overnight decrease of the slope, and if this alteration is linked to location and density of spike waves. In a retrospective study, the slope of slow waves (0.5-2Hz) in the first hour and last hour of sleep (19 electroencephalography [EEG] electrodes) of 14 patients with CSWS (3.1-13.5years) was calculated. The spike wave "focus" was determined as the location of highest spike amplitude and the density of spike waves as spike wave index (SWI). There was no overnight change of the slope of slow waves in the "focus." Instead, in "nonfocal" regions, the slope decreased significantly. This difference in the overnight course resulted in a steeper slope in the "focus" compared to "nonfocal" electrodes during the last hour of sleep. Spike wave density was correlated with the impairment of the overnight slope decrease: The higher the SWI, the more hampered the slope decrease. Location and density of spike waves are related to an alteration of the physiologic overnight decrease of the slow wave slope. This overnight decrease of the slope was shown to be closely related to the recovery function of sleep. Such recovery is necessary for optimal cognitive performance during wakefulness. Therefore we propose the impairment of this process by spike waves as a potential mechanism leading to neuropsychological deficits in CSWS. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.