Synchronization Interval Research Articles

Intermittent synchronization of resistively coupled chaotic Josephson junctions

Numerical simulations have been used to investigate the dynamics of a pair of resistively linked Josephson junctions with ac bias. For suitable choices of parameters, the chaotic states of the two junctions become intermittently synchronized. Intervals of synchronization are interleaved between bursts of desynchronized activity. The distributions of these laminar times and their dependence on the coupling strength are determined. The role of phase winding in the definition of synchronization intervals is considered.

Dual analyte flow injection fluorescence immunoassays using thiophilic gel reactors and synchronous scanning detection.

Heterogeneous fluorescence immunoassays have been automated using flow injection manifolds incorporating thiophilic gel solid phase reactors to separate antibody-bound and unbound analyte molecules. Antibody elution is achieved by changes in ionic strength, thus allowing the use of pH sensitive fluorescent labels. This facilitates the development of dual analyte systems, in which two competitive immunoassays with separate labels are monitored in parallel. Detection of the fluorophores by high speed synchronous fluorescence scanning while the flow is briefly stopped utilises either one synchronous interval which detects both fluorophores, or two separate scans at different wavelength intervals, one for each fluorophore. Simultaneous analyses of serum albumin and transferrin exemplify these novel approaches. Spectroscopic interferences are very small, analyte recoveries are close to 100%, with a relative standard deviation of 5-6% and a sampling rate of 20 h-1.

CHAOS SYNCHRONIZATION OF TWO PARAMETRICALLY EXCITED PENDULUMS

Two desynchronous parametrically excited chaos pendulums demonstrate a type of hyperchaotic behavior. This paper presents a periodic feedback scheme to synchronize the two pendulum subsystems. The synchronization principle is investigated. Feedback control parameters are discussed. The synchronous parameter intervals in which the maximum transverse Lyapunov exponent is negative guarantee the achievement of synchronization. Two originally unrelated tumbling chaos pendulums can be synchronized by this method in the intervals.

Existence Test for Asynchronous Interval Iteration

In the search for regions that contain fixed points of a real function of several variables, tests based on interval calculations can be used to establish existence or non-existence of fixed points in regions that are examined in the course of the search. The search can e.g. be performed as a synchronous (sequential) interval iteration: In each iteration step all components of the iterate are calculated based on the previous iterate. In this case it is straight forward to base simple interval existence and non-existence tests on the calculations done in each step of the iteration. The search can also be performed as an asynchronous (parallel) iteration: Only a few components are changed in each step and this calculation is in general based on components from different previous iterates. For the asynchronous iteration it turns out that simple tests of existence and non-existence can be based on the component wise calculations done in the course of the iteration. These component wise tests are useful for parallel implementation of the search, since the tests can then be performed local to each processor and only when a test is successful does a processor communicate this result to other processors.

Feasibility of atrial fibrillation detection and use of a preceding synchronization interval as a criterion for shock delivery in humans with atrial fibrillation

Objectives. This study assessed the feasibility of detecting atrial fibrillation (AF) and delivery of appropriately timed R wave shocks using an implantable atrial defibrillator.Background. For atrial defibrillation therapy to be feasible in an implantable form, AF must be detected in a specific fashion, and the risk of ventricular proarrhythmia should be minimized.Methods. Eleven patients with AF underwent testing with an implantable atrial defibrillator (METRIX 3000 Automatic Atrial Defibrillator, InControl, Inc.). Wideband electrograms (EGMs) were recorded from the right ventricular (RV) bipolar catheter and from the multipolar catheters located in the right atrium (RA) and coronary sinus (CS). Atrial fibrillation detection was performed using two serial algorithms—quiet interval analysis and baseline crossing analysis—that defect atrial activity on the RA-CS channel. Ventricular sensing using a minimal preceding synchronization interval of 500 ms as a criterion for synchronous shock delivery was performed from filtered RV and RV-CS EGMs.Results. The AF detection algorithms were applied to 53 AF data segments and 18 normal sinus rhythm data segments. Atrial fibrillation was detected appropriately in 49 instances, and the specificity for detecting AF and normal sinus rhythm was 100%. Synchronization criterion efficacy was assessed by delivering shock markers and shocks. Of the 2,025 R waves processed, 557 (27.5%) were marked as suitable for shock delivery. In addition, 69 therapeutic and 11 test shocks were delivered during AF. All shock markers and shocks were delivered synchronously with the R wave, and the synchronization criterion was never violated.Conclusions. Atrial fibrillation can be detected in a specific fashion using the RA-CS lead configuration and serial detection algorithms for atrial sensing. The delivery of properly timed shocks is feasible and should minimize the risk of ventricular proarrhythmia.

Beat-to-Beat Analysis of Left Ventricular Pressure-Volume Relation and Stroke Volume by Conductance Catheter and Aortic Modelflow in Cardiomyoplasty Patients

Since the clinical introduction of dynamic cardiomyoplasty, a discrepancy has been observed between unchanged measurements of cardiac function and improved clinical outcome. We performed a beat-to-beat analysis of cardiac performance at rest in nine cardiomyoplasty patients 6 to 24 months after operation. Conductance and micromanometer catheters were placed in left ventricle and aorta and used for measurements over a 15-second period, during which the wrapped latissimus dorsi (LD) muscle was stimulated for 10 seconds in a 1:2 synchronization mode followed by a 5-second period without LD stimulation. The synchronization delay between start of the QRS complex and the LD contraction was changed from 4 up to 125 ms at the patient's clinical stimulation strength and at an increased supramaximal amplitude. Comparing the LD assisted period to the unassisted period, at the clinical settings no significant changes in stroke volume (SV) as measured by the conductance technique and the aortic Modelflow technique were observed. A significant (P < .05) rise in left ventricular end-diastolic pressure (LVEDP) was observed directly after the assisted 10-second period. The peak ejection rate (PER) of left ventricular volume increased (P < .05), with a mean of 28 +/- 23% during the LD stimulated beats. At the patient's individual best setting, SV of the stimulated beats increased (P < .01) by a mean of 20 +/- 15%. Systolic aortic pressure increased (P < .01) by a mean of 7 mm Hg, peak negative dP/dt increased (P < .01), and PER increased, with a mean of 68 +/- 24% (P < .01). LVEDP was similar in stimulated and unstimulated beats and increased (P < .05) in the nonpaced 5-second period. The delay for the best setting ranged from 25 to 125 ms; the stimulus strength was 1.5 to 3 V higher than the clinical setting. At the patient's individual worst setting, SV remained unchanged and PER was higher, with a mean of 30 +/- 25% (P < .05). The worst setting was observed at the 1.5- to 3-V-higher stimulus strength; in six patients, it was at a short delay (4 to 25 ms) and in three patients, at the longest delay (100 to 125 ms). By the left ventricular conductance catheter and aortic Modelflow methods, improvement in cardiac function by dynamic cardiomyoplasty was demonstrated in this patient group. The synchronization interval, stimulus strength, and stimulus duration appeared to be critical for obtaining optimal improvement.

Incidence of Second Primary Cancers in Osaka Residents, Japan, with Special Reference to Cumulative and Relative Risks

This study was conducted to examine the incidence rates and cumulative risks of second primary cancers in Osaka and to compare the observed number of second primary cancers with the expected number calculated using cancer incidence rates among Osaka residents. Study subjects were all reported cases aged 0–79 who were first diagnosed as having a first primary cancer between 1966–86. Incidence of second primary cancer among the study subjects was examined through to the end of 1989. The total number of study subjects was 217,307. During the follow‐up period (mean duration: 3.7 years), second primary cancers developed in 5,071 patients (2.3%). Incidence of synchronous (interval <3 months) and metachronous (interval ≥ 3 months) second primary cancers increased in the later years. Incidence rates of second primary cancers were significantly associated with gender (male), age and calendar year at diagnosis of the first cancer. Based on the incidence rates, cumulative risk of developing metachronous second primary cancer was calculated. The ten‐year cumulative risk was estimated as 10% for those who developed their first cancer during their sixties in 1978–83. The observed number of second primary cancers (including synchronous) was compared with the expected number. The ratios of observed‐to‐expected numbers were generally lower than 1.0 among those who developed their first cancer in 1966–77, while these ratios were higher than 1.0 among those who developed their first cancer in 1978–86. The ratios were much higher than 1.0 among those who developed their first cancer in their childhood and youth. Patients who had developed cancer of the colon, larynx, lung, bladder, or breast (female) showed significantly higher risk of developing second primary cancer during the period 1–4 years after diagnosis of the first cancer.

Feedforward postural stabilization in a distal bimanual unloading task.

The aim of the present study was to investigate postural adjustments and positional stability in a bimanual unloading task, involving essentially the index finger, in order to test whether proactive adjustments are also observed in distal body segments. A second goal of the study was to evaluate the concept of a central command that would be responsible for coupling movement and posture. The positional disturbance of the right load-bearing index finger of healthy human subjects was studied under two types of manipulations: passive, i.e., imposed, unloading and active unloading, by the subject's left index finger. It was found that, in such a distal task, positional stabilization of the load-bearing finger was much better (by a factor of 6) in the active situation than the passive situation. This improvement was greater than previously reported for a proximal task. An electromyogram (EMG) analysis of the mostly implicated dorsal interosseous muscles revealed a typical unloading reflex in the passive situation (reactive mode) and a suppression of EMG before unloading onset in the active situation (proactive mode). Averaged records showed an almost perfect synchronization between the EMG suppression in the load-bearing interosseous muscle and the onset of the EMG burst of the unloading index finger. A trial-by-trial analysis, however, revealed a considerable scatter in intervals of the two EMG events, with a tendency of the activity burst in the left finger to occur slightly before the suppression of EMG in the load-bearing muscle. No positive correlation was found between the precision of synchronization (intervals near zero time) and the accuracy of performance, i.e., positional stability of the unloaded finger. Although the trial-by-trial variability was large, it is suggested that at least some of this variability is caused by a nonsteady state of motoneuronal excitability. In view of the low-pass property of the muscle, the observed variability in synchronization may be sufficiently precise to maintain the hypothesis of a central temporal coupling of the events in the two hands through a common command. However, the lack of a correlation between the degree of synchronization and the performance in stability argues rather in favor of separate commands to the two hands that select the parameters in the spatial domain. Finally, an intermanual EMG or torque analysis is proposed that might be useful in assessing the accuracy in goal achievement, i.e., the maintenance of a stable finger position in spite of the "internal" perturbation.

The Design and Development of a Codec for Two “Sound-in-Sync” Channels in a Television System

The transmission of multiple sound along with a single picture has many applications. In this work, two sound channels in addition to the one that normally accompanies a picture are time multiplexed with the television signal. The extra audio signals are coded with eight-bit PCM and placed in the horizontal synchronization interval of the video signal. At the receiver, these pulses are extracted to recover the audio signals. The prototype CODEC developed has shown satisfactory results for two extra speech channels over a normal television channel. The system can be used with a standard television receiver without any modifications by the addition of the decoding unit.

Some multivariate generalizations of results in univariate stationary point processes

Some relationships are derived between the asynchronous and partially synchronous counting and interval processes associated with a multivariate stationary point process. A few examples are given to illustrate some of these relationships.

Some multivariate generalizations of results in univariate stationary point processes

Some relationships are derived between the asynchronous and partially synchronous counting and interval processes associated with a multivariate stationary point process. A few examples are given to illustrate some of these relationships.

Synchronous and Asynchronous Distributions for Poisson Cluster Processes

Summary A simple relation between the synchronous and asynchronous distributions of a Poisson cluster process is proved. This is used in conjunction with the Palm–Khintchine equations to derive an expression for the counting distribution of such a process. It is shown that the synchronous inter-event intervals have coefficient of variation greater than or equal to one, and that the forward recurrence time has a non-increasing hazard function. An expression is derived for the joint survivor function for two consecutive synchronous intervals of a Bartlett–Lewis cluster process.

Response characteristics of neurons in the cochlear nuclei to sinusoidal and vowel-sound stimulation

The response characteristics of neurons in the dorsal (DCN) and ventral (VCN) cochlear nuclei of kangaroo rat (D. spectabilis) to sinusoids and trains of vowel segments are described. Synchronization coefficients, response areas, post-stimulus-time histograms, interval histograms, and period histograms are all used to compare functional features of neurons in the cochlear nuclei. Pauser and chopper-type neurons of DCN exhibited low discharge rates to vowel-segment sounds. Low-frequency DCN neurons which had low synchronization coefficients did not follow closely the vowel segment waveforms. The responses of VCN neurons with low best frequencies but high coefficients of synchronization occurred in temporal sequences which were closely related to the waveform within each vowel segment. This paper relates the subnuclear cytoarchitectonics of the cochlear nuclei and stimulus coding. [Supported by Air Force Office of Scientific Research.]

Selective interaction of a Poisson and renewal process: the spectrum of the intervals between responses

This paper is concerned with the spectrum of the intervals between responses in the renewal inhibited Poisson process, and continues the author's earlier work on this type of process ((1970a), (1970b), (1971)). A generating function for all the pairwise joint distributions of the synchronous intervals following an average response is obtained and leads directly to the associated serial correlations. It is shown that these correlations are equivalent to those predicted on different assumptions by the general stationary point theory. The results are then used to obtain the interval spectrum, and to exhibit a relationship between the sum of the serial correlations and the variance-time function. Explicit results for the spectrum of the renewal inhibited Poisson process are given for gamma inhibitory distributions, and the qualitative behavior is determined. Possible further developments are briefly discussed.

Selective interaction of a Poisson and renewal process: the spectrum of the intervals between responses

This paper is concerned with the spectrum of the intervals between responses in the renewal inhibited Poisson process, and continues the author's earlier work on this type of process ((1970a), (1970b), (1971)). A generating function for all the pairwise joint distributions of the synchronous intervals following an average response is obtained and leads directly to the associated serial correlations. It is shown that these correlations are equivalent to those predicted on different assumptions by the general stationary point theory. The results are then used to obtain the interval spectrum, and to exhibit a relationship between the sum of the serial correlations and the variance-time function. Explicit results for the spectrum of the renewal inhibited Poisson process are given for gamma inhibitory distributions, and the qualitative behavior is determined. Possible further developments are briefly discussed.

Development of time concepts in normal and retarded children.

36 normal and retarded children, matched for MA at three levels (6, 9, and 11, ns = 6 each), were tested for understanding of the time concepts of simultaneity, equality of synchronous intervals, and order of events. For both normals and retardates, active ordering of observed events was more difficult than understanding of simultaneity or of equality of synchronous intervals in observed demonstrations. Understanding of time concepts increased steadily with increases in MA, and a sequential order of development in rime concepts was indicated. Children at lower MAs understood simultaneity and equality of synchronous intervals better than active ordering of events, whereas at higher MAs these concepts were understood essentially equally. A slower rate of development by retardates than by normals was suggested by the results, but unequivocal acceptance of this finding was cautioned against due to confounding of IQ with MA level in the retarded Ss.

Selective interaction of a poisson and renewal process: the dependency structure of the intervals between responses

This paper studies the dependency structure of the intervals between responses in the renewal inhibited Poisson process, and continues the author's earlier work on this type of process ((1970a), (1970b)). A new approach to the intervals between events in a stationary point process, based on the idea of an average event, is introduced. Average event initial conditions (as opposed to equilibrium initial conditions previously determined) for the renewal inhibited Poisson process are obtained and event stationarity of the resulting response process is established. The joint distribution and correlation between pairs of contiguous synchronous intervals is obtained; further, the joint distribution of non-contiguous pairs of synchronous intervals is derived. Finally, the joint distributions of pairs of contiguous synchronous and asynchronous intervals are related, and a similar but more general stationary point result is conjectured.

Selective interaction of a poisson and renewal process: the dependency structure of the intervals between responses

This paper studies the dependency structure of the intervals between responses in the renewal inhibited Poisson process, and continues the author's earlier work on this type of process ((1970a), (1970b)). A new approach to the intervals between events in a stationary point process, based on the idea of an average event, is introduced. Average event initial conditions (as opposed to equilibrium initial conditions previously determined) for the renewal inhibited Poisson process are obtained and event stationarity of the resulting response process is established. The joint distribution and correlation between pairs of contiguous synchronous intervals is obtained; further, the joint distribution of non-contiguous pairs of synchronous intervals is derived. Finally, the joint distributions of pairs of contiguous synchronous and asynchronous intervals are related, and a similar but more general stationary point result is conjectured.

Adaptive Optimum Detection: Synchronous-Recurrent Transients

Adaptive optimum-detection theory is applied to the problem of detecting a recurrence phenomenon in noise. This phenomenon consists of one of a finite number of possible transient waveforms whose temporal uncertainty is synchronous Poisson. The optimum (likelihood ratio) receiver is designed from the viewpoint of obtaining a receiver implementation with a practical memory size while at the same time maintaining optimum-detection performance. The optimum detector for the synchronous-Poisson case recirculates and averages a nonlinear function of the input data in contrast to the optimum detector for the periodic case that recirculates and averages the input data itself. The detection performance is evaluated, and the receiver operating characteristics (ROC) are presented as a function of average duty factor ν, number of synchronous intervals k, transient waveform energy Ec ,and the noise power per unit bandwidth N0. At low transient signal-to-noise ratios and low average duty factors, the detectability d is given approximately by ν2k (2Ec/N0). The effect of transient uncertainty on detectability is also presented on the ROC.