Wave Downslope Research Articles

Broaching-to prevention in real-time using momentary state feedback control focusing on the saddle point in the system

For realizing real-time broaching-to prevention in regular waves, the momentary state feedback control in the vicinity of the saddle point of the dynamical system is newly proposed, based on the previous work (Maniyappan in J Mar Sci Technol, 2020, https://doi.org/10.1007/s00773-020-00743-4). This is an extension of the concept of OGY (Ott, Grebogi, and Yorke) (Ott in Phys Rev Lett 64:1196–1199, 1990) algorithm by applying momentary state feedback using the linear-quadratic regulator (LQR) only when the ship approaches a saddle point. It was numerically confirmed in regular waves that controlling the surging in a wave downslope during broaching-to enables to change the broaching to a periodic motion at lower Froude number. At higher Froude numbers, broaching-to prevention is achieved by undergoing stable surf-riding near the wave trough in lower heading angles. The robustness of the controller towards modeling uncertainties and limitation of the observed variables are also confirmed by using a controller model that ignores the nonlinear terms in the calm-water manoeuvring forces and the longitudinal position of the ship to waves.

P4507Left atrial conduit function modulates functional capacity in heart failure patients acting through the pulsatile component of right ventricular afterload

Abstract Background It has been suggested that left atrial (LA) characteristics modulate the functional capacity in heart failure (HF) patients through the impact that LA cavity exerts on the pulmonary circulation and the pulsatile component of right ventricular (RV) afterload, as represented by pulmonary arterial compliance (PAC). Purpose Thus, we hypothesized that, in a HF patients' population, a larger relative contribution of LA phasic conduit function (PCF) to the left ventricular (LV) stroke volume would be associated with a heavier right ventricular hemodynamic burden and a reduced functional capacity. Methods 60 sinus rhythm HF subjects (42 males, 67±11 years, ejection fraction [EF] 39±11%, range 20% - 62%) underwent 6 minute walking test (6MWT) and routine transthoracic echocardiography, plus real time 3D acquisitions analyzed with a dedicated echo software package. LV ejection fraction (EF) was obtained from 3D echo acquisitions. LV diastolic dysfunction (DD) was assessed according to current guidelines. Computation of PCF was made by simultaneous gathering real time 3D multibeats (6 cycles) LA and LV volumes, using the formula: PCF(time) = [LV(time) − LV minimum] − [LA maximum − LA(time)] as proposed by Bowman & Kovacs (2004), with PCF expressed as % of LV stroke volume. Atrioventricular compliance (Cn) was also assessed, as proposed by Flachskampf et al. (1992): 1270*(mitral valve area/E wave downslope) and expressed in ml/mmHg. Finally, PAC was obtained as the ratio between RV stroke volume (pulmonary velocity time integral*pulmonary valve annulus area measured from the RV outflow tract diameter) and pulse pressure (obtained from pulmonary and tricuspid regurgitant envelopes) and expressed in ml/mmHg. Results Maximal LA and LV volumes averaged 69±21 ml and 147±47 ml, respectively. The mean value of PCF was 33±12% (range 7% - 58%). Mean 6MWT was 397±162 m. Mean PAC was (3.1±1.1 ml/mmHg). DD grade I, II and III were detected in 38 (63%), 18 (30%) and 4 (7%) of the patients' population, respectively. PCF was independent of LA or LV volumes and EF, but showed a strong direct relation with DD (r=0.62; p<0.0001) and a relevant inverse dependence on Cn (r=−0.48; p=0.0001). For a comparable Cn, dividing patients into tertiles according to 6MWT, it was clear that highest PCF was significantly associated with lowest functional capacity (ANCOVA, figure left). Similarly, dividing patients into tertiles according to PAC, it emerges that highest PCF is significantly associated with most deranged PAC (ANCOVA, figure right), suggesting outmost RV hemodynamic burden. Conclusion PCF is an important parameter to be quantified in HF patients that is dependent on global left heart compliance, being affected by DD, but not LV EF. Furthermore, at a given Cn, PCF is increased in HF patients with lowest functional capacity, likely because RV pulsatile afterload is highest in these subjects.

Binaural interaction in the auditory brainstem response: A normative study

ObjectiveBinaural interaction can be investigated using auditory evoked potentials. A binaural interaction component can be derived from the auditory brainstem response (ABR–BIC) and is considered evidence for binaural interaction at the level of the brainstem. Although click ABR–BIC has been investigated thoroughly, data on 500Hz tone-burst (TB) ABR–BICs are scarce. In this study, characteristics of click and 500Hz TB ABR–BICs are described. Furthermore, reliability of both click and 500Hz TB ABR–BIC are investigated. MethodsEighteen normal hearing young adults (eight women, ten men) were included. ABRs were recorded in response to clicks and 500Hz TBs. ABR–BICs were derived by subtracting the binaural response from the sum of the monaural responses measured in opposite ears. ResultsGood inter-rater reliability is obtained for both click and 500Hz TB ABR–BICs. The most reliable peak in click ABR–BIC occurs at a mean latency of 6.06ms (SD 0.354ms). Reliable 500Hz TB ABR–BIC are obtained with a mean latency of 9.47ms (SD 0.678ms). Amplitudes are larger for 500Hz TB ABR–BIC than for clicks. ConclusionThe most reliable peak in click ABR–BIC occurs at the downslope of wave V. Five hundred Hertz TB ABR–BIC is characterized by a broad positivity occurring at the level of wave V. SignificanceThe ABR–BIC is a useful technique to investigate binaural interaction in certain populations. Examples are bilateral hearing aid users, bilateral cochlear implant users and bimodal listeners. The latter refers to the combination of unilateral cochlear implantation and contralateral residual hearing. The majority of these patients have residual hearing in the low frequencies. The current study suggests that 500Hz TB ABR–BIC may be a suitable technique to assess binaural interaction in this specific population of cochlear implant users.

Abstract 9855: Presence of J-waves or Slurs in Chest Pain Patients Predicts Higher Mortality in those Diagnosed as Acute Myocardial Infarction

BACKGROUND: Although early repolarization is known as a benign, J-waves or slurs on the R wave downslope have recently been associated with sudden cardiac death. We investigated the presence and prognostic significance of R wav downslope phenomena in patients presenting chest pain at the emergency department. METHODS: We performed a retrospective study of 747 chest pain patients. The presence of a J-wave or slurs in the 12-lead resting ECG recorded at the emergency department was defined as a QRS notching and or QRS slurring of more than 0.1mV relative to the PR-interval (QRSonset) as coded by a single observer using enhanced imaging (RA). Final diagnosis was adjudicated by two independent cardiologists having access to all acquired data including a 2 year follow-up period. Results: Of the participants (mean of age 61.9, 67.1% males), 16% had an acute myocardial infarction, 17% an unstable angina, 12% with cardiac symptoms other than CAD, 46% non-cardiac symptoms and 9% symptoms of unknown origin. There was a significant correlation between patients presenting J-waves/slurs and days in hospital (p=0.04), know hypertonia (p=0.003), known CAD (p=0.05), prior MI (p=0.04), and presence of T negativity (p=0.005) but no significant correlation with ST-segment elevation or depression. There was a significant lower survival rate (0.90 versus 0.94, p=0.03, HR=1.81) in presence of J-waves primarily due to the AMI subgroup (0.72 versus 0.94, p=0.002, HR=4.71). CONCLUSIONS: From this analysis we found an overall association between comorbidities and the presence of J-waves or slurs at the emergency department. A significant higher mortality rate in patients J-waves or slurs was only found in patients who evolved AMI.

Broaching prediction in the light of an enhanced mathematical model, with higher-order terms taken into account

We have attempted to develop a more consistent mathematical model for capsizing associated with surf-riding in following and quartering waves by taking most of the second-order terms of the waves into account. The wave effects on the hull maneuvring coefficients were estimated, together with the hydrodynamic lift due to wave fluid velocity, and the change in added mass due to relative wave elevations. The wave effects on the hydrodynamic derivatives with respect to rudder angles were estimated by using the Mathematical Modelling Group (MMG) model. Then captive ship model experiments were conducted, and these showed reasonably good agreements between the experiments and the calculations for the wave effects on the hull and the rudder maneuvring forces. It was also found that the wave effects on restoring moments are much smaller than the Froude–Krylov prediction, and the minimum restoring arm appears on a wave downslope but not on a wave crest amidship. Thus, an experimental formula of the lift force due to the heel angle of the ship is provided for numerical modelling. Numerical simulations were then carried out with these second-order terms of waves, and the results were compared with the results of free-running model experiments. An improved prediction accuracy for ship motions in following and quartering seas was demonstrated. Although the boundaries of the ship motion modes were also obtained with both the original model and the present one, the second-order terms for waves are not so crucial for predicting the capsizing boundaries themselves.

Calculation of atrioventricular compliance from the mitral flow profile: analytic and in vitro study

The quantitative assessment of ventricular diastolic function is an important goal of Doppler echocardiography. Hydrodynamic analysis predicts that the net compliance (Cn) or the left atrium and ventricle can be quantitatively predicted from the deceleration rate (dvdt) of the mitral velocity profile by the simple expression: Cn= − Aϱdt where A is effective mitral valve area and ϱ is blood density.This formula was validated using an in vitro model of transmitral filling where mitral valve area ranged from 0.5 to 2.5 cm2and net compliance from 0.012 to 0.023 cm3/(dynes/cm2) (15 to 30 cm3/mm Hg). In 34 experiments in which compliance was held constant throughout the filling period, net atrioventricular compliance was accurately calculated from the E wave downslope and mitral valve area (r = 0.95, p < 0.0001).In a second group of experiments, chamber compliance was allowed to vary as a function of chamber pressure. When net compliance decreased during diastole (as when the ventricle moved to a steeper portion of its pressure-volume curve), the transorifice velocity profile was concave downward, whereas when net compliance increased, the velocity profile was concave upward. Application of the preceding formula to these curved profiles allowed instantaneous compliance to be calculated throughout the filling period (r = 0.93, p < 0.001). Numeric application of a mathematic model of mitral filling demonstrated the accuracy of this approach in both restrictive and nonrestrictive orifices.It is concluded that 1) net compliance can be calculated noninvasively and quantitatively from mitral valve area and E wave downslope, and 2) the time course of net compliance determines the shape of the downslope: concave downward profiles indicate decreasing compliance whereas concave upward profiles indicate increasing compliance.