Mode Switching Events Research Articles

Ex-post correction of pacemaker mode switch episodes in undersensed atrial fibrillation

BackgroundInformation about short Atrial Fibrillation (AF) episodes can be gathered from the diagnostic records of cardiac implantable electronic devices (CIEDs). CIEDs are not accurate when detecting short arrhythmia episodes. The correlation between mode switching events and AF episodes is significant for long events but prone to errors for short episodes. MethodsExpectation-maximization algorithms are used to estimate the parameters of a mathematical model from a list of AF episodes produced by the CIED. The durations of some of the episodes may be missing. Abnormal mode changes are detected and short episodes are joined into longer events when appropriate. The proposed method does not require that the sensitivity parameters of the device are altered. Post-processing of the data is limited to the detection of false negatives, thus paroxysmal arrhythmia diagnostic evaluations are safer. ResultsA three year-long study was carried out with patients with dual-chamber pacemakers (PM) at the Hospital Universitario Central de Asturias (Spain) between 2012 and 2015. The number of patients in which the proposed algorithm altered the final histogram was 40 out of 76. On average, the algorithm removes 2.79% of episodes shorter than 1 min in length and finds that 1% of the previously unaccounted episodes are longer than 30 min, of which 16% are longer than 24 h. ConclusionThe method is stable and guarantees that long arrhythmia episodes are never eliminated, and at the same time it is the most similar to the human expert in finding new long episodes.

Детекция событий разного типа в гибридных динамических системах

Hybrid dynamical or simply hybrid systems (HS) are a modern apparatus for modeling discrete-continuous processes in different applications such as power engineering, aeronautics, manufacturing, economics, transport dispatching, etc. The key difference of HSs from classical dynamic systems is the presence of continuous mode switching events. Event times are defined by the zeroes of continuous event functions. If it is impossible to symbolically compute an event time. To do it one uses an event detection algorithm working together with a differential equation integration algorithm. Events in HSs are traditionally divided into state events and time events. Only explicit time events with event functions in the form of linear polynomials in time are usually considered in the literature. This paper addresses the class of implicit time events and lists their possible sources. Moreover, the traditional classification of events into unilateral, bilateral and accuracy critical events is expanded by adding difficult-to-detect events. These events are characterized by event functions crossing zero several times within one integration step. Not all algorithms can guarantee detecting events of this type. Heterogeneous HSs including processes of different physical nature are in general characterized by significantly stiff and high-dimensional modes usually defined in a form of differential-algebraic systems of equations with events of different types. The last feature limits the application of classical event detection algorithms oriented to a single event type. That is why the paper proposes the methodology of complex event detection consisting in using separate event detection algorithm for each event type. The joint work of several algorithms can ensure correct detection of events of different types and also may improve the efficiency. A complex event detection algorithm guaranteeing detection of all events is constructed for a particular HS. The complex algorithm demonstrates an average speed up of 17%.

Response modes of erythrocytes in high-frequency oscillatory shear flows

Due to its capability of duplicating the deformation scenario of erythrocytes (red blood cells), in in vivo time scales, passing through interendothelial slits in the spleen, the understanding of the dynamic response of erythrocytes in oscillatory shear flows is of critical importance to the development of an effective in vitro methodology to study the mechanics, metabolism, and aging procedure in vivo [R. Asaro et al., “Erythrocyte aging, protection via vesiculation: An analysis methodology via oscillatory flow,” Front. Physiol. 9, 1607 (2018)]. Accordingly, we conducted a systematic computational investigation of the dynamics of erythrocytes in high-frequency oscillatory shear flows by using a fluid-cell interaction model based on the Stokes-flow framework and a multiscale structural depiction of the cell. Within the range of parameters we consider, we identify five different response modes (wheeling, tilted wheeling, tank treading mode 1, tank treading mode 2, and irregular). The occurrence and stability of these response modes depend on the frequency of the flow, the peak capillary number, the viscosity ratio, the initial orientation of the cell, and the stress-free state of the protein skeleton. Through long-term simulations [O(102) periods], mode switching events have been discovered, during which the cell transfers from one mode to another, often via an intermediate transient mode. The deformation of the skeleton and the contact stress between the skeleton and the lipid bilayer are computed since these are of direct importance to describing vital cell phenomena such as vesiculation by which the cell protects itself from premature elimination.

The mode switching of PSR B2020+28

This paper reports on polarimetric radiation properties based on the switching modes of normal PSR B2020+28 by analysing the data acquired from the Nanshan 25-m radio telescope at 1556 MHz. With nearly 8 hours quasi-continuous observation, the data presented some striking and updated phenomena. The change of relative intensity between the leading and trailing components is the predominant feature of mode switching. The intensity ratio between the leading and trailing components are measured for the individual profiles averaged over 30 seconds. It is found that there is an excess of high ratios over the normal distribution, which indicates that two modes exist in the pulsar. The distribution of abnormal mode has a narrower width indicating that the abnormal mode is more stable than the normal mode. A total of 76 mode switching events are detected in our data. It spends 89\% in the normal mode and 11\% in the abnormal mode. The intrinsic distributions of mode timescales are constrained with power-law distributions. The significant difference in the index of the duration distribution between normal and abnormal modes possibly indicates that the timescale for the abnormal mode to get stable is shorter than that for the normal mode. The frequent switching between both modes may indicate that the oscillations between different magnetospheric states are rapid.

Effect of equivalence ratio on the modal dynamics of azimuthal combustion instabilities

The present paper investigates the effect of equivalence ratio on the modal dynamics of self-excited azimuthal combustion instabilities in a laboratory-scale annular combustor. It is shown that operating at different equivalence ratios not only affects the mode of oscillation (whether the instabilities are mixed, or predominantly spinning or standing modes), but also the way in which mode switching between these states occurs. Using pressure time-series data obtained at multiple locations around the annulus the phenomenon of mode switching is investigated through the spin ratio, the orientation of the nodal lines and the envelope of the pressure oscillations. These three parameters all suggest that mode switching events occur almost periodically, and over azimuthal convective time scales. Moreover, analysis of the spin ratio and orientation of the nodal lines show that these parameters are correlated, and that their mean rates of change or trajectories also have a preferred direction. Therefore, these quantities were found to oscillate backwards and forwards in-phase with each other, as opposed to the mode simply rotating in one direction, providing new insight into the nature of modal dynamics of self-excited azimuthal modes.

Mode-switching induced super-thermal bunching in quantum-dot microlasers

The super-thermal photon bunching in quantum-dot (QD) micropillar lasers is investigated both experimentally and theoretically via simulations driven by dynamic considerations. Using stochastic multi-mode rate equations we obtain very good agreement between experiment and theory in terms of intensity profiles and intensity-correlation properties of the examined QD micro-laser’s emission. Further investigations of the time-dependent emission show that super-thermal photon bunching occurs due to irregular mode-switching events in the bimodal lasers. Our bifurcation analysis reveals that these switchings find their origin in an underlying bistability, such that spontaneous emission noise is able to effectively perturb the two competing modes in a small parameter region. We thus ascribe the observed high photon correlation to dynamical multistabilities rather than quantum mechanical correlations.

RECENT PROGRESS ON PULSAR OBSERVATIONS AT NANSHAN

Recent results of pulsar observations at Nanshan are present in this paper. In total 47 glitches were detected in the young pulsars, including a giant glitch in PSR B2334+61. We also investigated the scintillation parameters with the quasi-continuous observations of PSR B0329+54 spanning twenty days. Mainly using the same dataset, consecutive mode-switching events were analyzed in pulse profiles of PSR B0329+54.

Simultaneous fault and mode switching identification for hybrid systems based on particle swarm optimization

This paper describes a methodology for simultaneous identification of fault parameters and mode switching events for hybrid systems. The method is developed based on the notion of Global Analytical Redundancy Relations (GARRs) from the bond graph model of the hybrid system. A unified formula with mode change time sequence and initial mode coefficients (IMC) is derived to represent the mode switching. Due to the discontinuous characteristic of the mode switching, an adaptive hybrid particle swarm optimization (AHPSO) employing the combination of real valued PSO (RPSO) and binary valued PSO (BPSO) is proposed to optimize different parts of solution simultaneously, a novel individual level adaptive method using fuzzy system is developed to dynamically adjust the algorithm parameters. GARRs are used as a fitness index of the AHPSO. Case studies of different energy domains are carried out to illustrate the efficiency of the proposed algorithm.

Follow-up of pacemaker after radiofrequency atrioventricular junction ablation

Purpose of study Follow-up dynamic of dual chamber pacing with auto switch mode (ASM) function after atrioventricular (AV) junction ablation in patients with paroxysmal atrial fibrillation (AF) was evaluated. Methods In 65 patients (42 male, 23 female), mean age 66±7,9 years with paroxysmal AF radiofrequency (RF) ablation of AV junction with implantation of DDDR pacemaker with ASM function were performed. Each patient was evaluated every 3 months during a 15,3±2,3 month period. We analysed the quantity of mode switching events and their duration, maximal atrial rate during paroxysm and proportion of atrial sensing-ventricular pacing (As-Vp), atrial-ventricular pacing (Ap-Vp) and VVI pacing (Vp). The atrial statistic of pacemaker was the point of special assessment. Results According the results of atrial statistic sensing of AF paroxysms was adequate. In the first 3 months of after operation pacemaker detection of high atrial rate was checked by external Holter monitor. The number of paroxysmal AF episodes recorded during first 3 months were 59±17,2 and during the last – 41,2±11,2 (p=0,01); the decrease of duration in mode switching was from 192,5±51,1 min to 98,5±41,2 min (p<0.05); the duration of each AMS event shortened significantly – from 7,8±3,1 min to 1,9±1,3 min (p=0,02). The proportion of As-Vp was similar (p=NS) in both pacing modes. Symptomatic improvement was reported by all patients, while hospital visits were for ordinary pacemaker follow-up. No patient experienced pacemaker dysfunction in terms of sensing and pacing threshold. Conclusion AV junction ablation with permanent DDDR pacing with ASM is a reliable method of arrhythmia control and improvement of quality of life. It seems that atrial pacing may be a stabilising factor in patients with paroxysmal AF even if they have intact sinus node function. Results of atrial statistic of pacemaker should be implemented for analysis and correction of pacemaker program in patients with AF.