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Aoyagi, Naoko, Kyoko Ohashi, Shinji Tomono, and Yoshiharu Yamamoto. Temporal contribution of body movement to very long-term heart rate variability in humans. Am J Physiol Heart Circ Physiol 278: H1035-H1041, 2000.--A newly developed, very long-term (~7 days) ambulatory monitoring system for assessing beat-to-beat heart rate variability (HRV) and body movements (BM) was used to study the mechanism(s) responsible for the long-period oscillation in human HRV. Data continuously collected from five healthy subjects were analyzed by 1) standard auto- and cross-spectral techniques, 2) a cross-Wigner distribution (WD; a time-frequency analysis) between BM and HRV for 10-s averaged data, and 3) coarse-graining spectral analysis for 600 successive cardiac cycles. The results showed 1) a clear circadian rhythm in HRV and BM, 2) a 1/[f.sup.[Beta]]-type spectrum in HRV and BM at ultradian frequencies, and 3) coherent relationships between BM and HRV only at specific ultradian as well as circadian frequencies, indicated by significant (P [is less than] 0.05) levels of the squared coherence and temporal localizations of the covariance between BM and HRV in the cross-WD. In a single subject, an instance in which the behavioral (mean BM) and autonomic [HRV power [is greater than] 0.15 Hz and mean heart rate (HR)] rhythmicities were dissociated occurred when the individual had an irregular daily life. It was concluded that the long-term HRV in normal humans contained persistent oscillations synchronized with those of BM at ultradian frequencies but could not be explained exclusively by activity levels of the subjects. ambulatory monitor; circadian rhythm; behavior; autonomic; human

Juhl, Claus B., Niels Porksen, Jeppe Sturis, Age Prange Hansen, Johannes D. Veldhuis, Steven Pincus, Mark Fineman, and Ole Schmitz. High-frequency oscillations in circulating amylin concentrations in healthy humans. Am. J. Physiol. Endocrinol. Metab. 278: E484-E490, 2000.--Amylin is stored in the pancreatic [Beta]-cell granules and cosecreted with insulin in response to nutrient stimuli. To gain further insight into control of hormonal release in [Beta]-cell physiology, we examined whether amylin, like insulin, circulates in a high-frequency oscillatory pattern, and if it does, to compare the secretory patterns of the two hormones. Eight overnight-fasted healthy individuals were studied during intravenous glucose infusion (2.0 mg [multiplied by] [kg.sup.-1] [multiplied by] [min.sup.-1]). Blood was collected every minute for 90 min and analyzed in triplicate for amylin, total amylin immunoreactivity (TAI), and insulin. Mean plasma concentrations of amylin (nonglycosylated), TAI (nonglycosylated plus glycosylated), insulin, and glucose were 2.77 [+ or -] 1.21 pmol/l, 7.60 [+ or -] 1.73 pmol/l, 50.4 [+ or -] 17.5 pmol/l, and 5.9 [+ or -] 0.3 mmol/l, respectively. The 90-min time series of amylin, TAI, and insulin were analyzed for periodicity (by spectral analysis, autocorrelation analysis, and deconvolution analysis) and regularity [by approximate entropy (ApEn)]. Significant spectral density peaks were demonstrated by a random shuffling technique in 7 (out of 7), 8 (out of 8), and 8 (out of 8) time series, respectively, whereas autocorrelation analysis revealed significant pulsatility in 5 (out of 7), 7 (out of 8), and 5 (out of 8), respectively. The dominant periodicity of oscillations determined by spectral analysis was 4.6 [+ or -] 0.3, 4.6 [+ or -] 0.4, and 6.5 [+ or -] 1.1 min/pulse, respectively (amylin vs. insulin, P = 0.017, TAI vs. insulin, P = 0.018). By deconvolution analysis, amylin and insulin periodicities were, respectively, 6.3 [+ or -] 1.0 and 5.5 [+ or -] 0.6 min. By application of the regularity statistic, ApEn, 6 (out of 7), 7 (out of 8), and 6 (out of 8), respectively, were found to be significantly different from random. In conclusion, like several other hormones, circulating amylin concentrations exhibit oscillations in the secretory patterns for nonglycosylated as well as glycosylated forms. Whether the high-frequency pulsatile release of amylin is disturbed in diabetes is not known. amylin secretion; insulin secretion; amylin pulsatility

We present a direct method for the steady-state and stability analysis of autonomous circuits with transmission lines and generic nonlinear elements. With the discretization of the equations that describe the circuit in the time domain, we obtain a nonlinear algebraic formulation where the unknowns to determine are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is described. Without any modification in the analysis method, the stability of the solution can be computed a posteriori constructing an implicit map, where the last sample is viewed as a function of the previous samples. The application of this technique to the time-delayed Chua's circuit (TDCC) allows us to investigate the stability of the periodic solutions and to locate the period-doubling bifurcations. Index Terms--Autonomous circuits, bifurcation points, distributed, nonlinear, steady-state response, stability analysis, time-domain discretization.

In this paper, an analytical method of an orthogonal-core type parametric induction motor is proposed, based on a reluctance network model of the stator. The model is derived by a similar technique applied to an orthogonal-core transformer. Using this model the parametric oscillation characteristic of the motor, without a rotor, is computed. Tile simulation results agree well with the experiments. It is obvious that the analytical model of tile stator presented here is proper for analysis of tile motor and that, by use of this model and suitable analytical model of the rotor, the motor characteristics can be analyzed. Index Terms -- Nonlinear magnetics, orthogonal-core, parametric motor, reluctance network analysis.

Over the recent past, efforts have been made to overcome fabrication issues with superconducting nanoscale wires in order to enable faster and more powerful electronic devices. However, these efforts have [...]

A study reports that a rhodium(III) porphyrin cyclic dimer forms a supramolecular oscillator with carbon nanocluster. An inclusion complex of a cyclic dimer of rhodium(III) porphyrin with C120 serves as a novel supramolecular oscillator, which can visualize the salvation desolvation dynamics of carbon nanoclusters.

The steady-state response of the classic mass-spring-dashpot model when the spring stiffness decays exponentially with time (an aging spring) and the system is excited by a forcing function whose frequency is equal to the natural frequency of the system with the constant initial stiffness is investigated. The steady-state response is obtained in terms of the damping and decay constants of the system and exhibits an oscillation about a nonzero value. [DOI: 10.1115/1.1458559]

This paper deals with nonlinear oscillation of a general single-degree-of-freedom system. By combining the linearization of the governing equation with the method of harmonic balance, we establish two analytical approximate formulas for the period. These two formulas are valid for small as well as large amplitudes of oscillation. [DOI: 10.1115/1.1406960]

A laboratory apparatus which can be utilized to illustrate the normal modes of mechanical oscillations in the linear string and air column of a circular loop is presented. The stationary states with an integral number of wavelengths, representing the quantization in loops at very low frequencies in the range 0.2 to 2.0 Hz can easily be set up with the apparatus. The device is composed of 20 simple pendula. These pendula are mounted on a bicycle rim. The masses are interconnected with a thin metallic strip in a loop to couple all the pendulums.

An inverted pendulum can be balanced using an oscillating system which provides stability. One such system involves a magnet supported by an ac magnetic field. More recent designs of this oscillating system uses both ac and dc magnetic fields to support the magnet. The floating magnet can be regarded as a short dipole, with the ac coil providing a vertical oscillating field. The geometry and symmetrical filamentry of the turns in an optimum ac coil are presented.

Machines with high accuracy are widely used in industries. In such machines, the degree of accuracy depends upon the environmental factors, among others. For example, a shop floor containing various [...]

Researchers from Spain report theoretical phase diagrams of II-VI dilute magnetic semiconductors for use as spin injectors. They investigate an n-doped dc-voltage-biased ZnSe/(Zn, Cd)Se multi-quantum-well nanostructure doped with manganese as [...]

06-1782 Muller, I., J. Schmidt, and P. Vielsack. Parametric updating of non-smooth FE-models for nonlinear vibration-based damage identification. Proceedings of the Twelfth International Congress on Sound and Vibration, Lisbon, Portugal: [...]

06-1450 Dimitriadis, G., G.A. Vio, and J.E. Cooper. Stability and limit cycle oscillation amplitude prediction for multi-DOF aeroelastic systems with piecewise linear non-linearities. Proceedings of the 2004 International Conference on [...]

A dynamic artificial neural network in the form of a multilayer perceptron with a delayed recurrent feedback connection is investigated to determine its ability to predict linear and nonlinear flutter response characteristics. Flight-test results show that limit cycle oscillation (LCO) response characteristics are strongly dependent on Mach number in the transonic flight regime. This effect is also evident in the classical transonic small-disturbance theory governing equations. A dynamic network is considered in order to examine the effects of sequential Mach-number dependence on the network's predictive capability. The architecture of a dynamic network allows for modeling data dependent on a sequentially or linearly increasing parameter (usually time, but in this case Mach number). The predictive capabilities are compared to those of a static artificial neural network. The network is developed and trained using linear flutter analysis and flight-test results from a fighter test. Eleven external store carriage configurations are used as training data, and three configurations are used as test cases. The dynamic network was successful in predicting the aeroelastic oscillation frequency and amplitude responses over a range of Mach numbers for two of the test cases. The dynamic network showed slightly better correlation to flight-test results for the typical LCO test case but slightly worse correlation for the flutter case. Predictions for the nontypical LCO test case were not good for either network.

This paper investigates the effect of element value deviation on the degenerate mode in rings of three and four coupled van der Pol oscillators. By using the averaging method, we elucidate that the element value deviation has different effects on the rings of three and four coupled oscillators. Namely, for the ring of three coupled oscillators, two single modes which bifurcate from the twofold degenerate mode in the symmetric system can be synchronized when they are close, but they lose synchronization and a quasiperiodic oscillation appears when they are separated to some extent. In contrast, for the ring of four coupled oscillators, the two single modes cannot be synchronized, even if they are close. However, in some rare cases they can be synchronized when they are separated to some extent. We confirm these results of the averaging method by both computer simulation and experiments. Index Terms - Asymmetric system, averaging method, degenerate modes, element value deviation, rings of coupled oscillators.

A simple trigonometry approximation introduced in 1950 is used to examine the large amplitude torsional oscillation observed in the Tacoma Narrows Bridge. This study regenerates a mechanical model for a beam or plate that is oscillating torsionally about equilibrium and hanging at both sides or ends by cables. Analysis demonstrates that the geometry of the situation are enough to account for the large amplitude oscillations witnessed before the collapse of the bridge.

Synchronization of neural activity in oscillatory neural networks is a general principle of information processing in the brain at both preattentional and attentional levels. This is confirmed by a model of attention based on an oscillatory neural network with a central element and models of feature binding and working memory based on multi-frequency oscillations.

A theoretical method that accounts for diffraction and backcoupling of surface plasmon (SP) oscillations excited at the metallized edge of a planar waveguide is described in this paper. The model explains previously reported experimental studies related to the development of SP-based optical-fiber sensors. The method is based on a Fourier transform approach and predicts the appearance of a spatial SP resonance within the light diffracted from the waveguide edge. The approach also allows one to obtain the spectral dependence of light guided back from the remote waveguide edge and can be used to determine design parameters for optimum sensor operation. Index Terms-- Aluminum, diffraction, gold, optical fiber, optical waveguide, slab waveguide, surface plasmon oscillations, surface plasmon resonance, thin film.

The inner-core of the earth regulates magnetic reversals, and oscillations in the geomagnetic dipole may be good indicators of these magnetic changes. Full reversals arise from large oscillations. The expulsion of magnetic flux beneath the South Atlantic may be responsible for the oscillations. The external section of the inner-core cylinders with expulsion of flux inhibits the dynamo action and renders stability to the inner-core.