Inherent Frequencies Research Articles

Instability of a strong pulse current in a tungsten plate

The instability of a strong pulse current is observed in a plate of pure tungsten. The instability appears at low temperatures if the plate is placed in a high magnetic field parallel to the current direction. The magnetic field of the alternating current in the sample is detected by making use of a Hall probe. The inherent frequencies of the instability currents are some tens of hertz. Their amplitude ranges up to about hundreds of milliamperes. The primary directions of the instability fields are along the steady magnetic fields, so that the instability currents have a component at right angles to the initial current direction. There is a threshold value of the amplitude of the pulse current at the beginning of instability. It has been found that the threshold value depends on the steady magnetic induction and is reduced significantly when the induction increases. The amplitude of the instability currents under study exhibits features of the dynamical chaos regime. The conversion into the chaos regime is effected by the formation of turbulent time intervals intermittent with laminar time intervals. It was found experimentally that the occurrence of the current instability is accompanied by ultrasonic oscillations. The observed instability is attributable to the fact that the magnetic field of the current pulses changes the trajectories of electrons. A set of equations has been proposed in order to explain the oscillatory behaviour of the fields of instability. This set contains two differential equations of parabolic type like the distributed parameter system with diffusion.

Conditional dendritic oscillators in a lobster mechanoreceptor neurone.

1. Intra- and extracellular recordings were made from in vitro preparations of the lobster (Homarus gammarus) stomatogastric nervous system to study the nature and origin of pacemaker-like activity in a primary mechanoreceptor neurone, the anterior gastric receptor (AGR), whose two bilateral stretch-sensitive dendrites ramify in the tendon of powerstroke muscle GM1 of the gastric mill system. 2. Although the AGR is known to be autoactive, we report here that in 20% of our preparations, rather than autogenic tonic discharge, the receptor fired spontaneously in discrete bursts comprising three to ten action potentials and repeating at cycle frequencies of 0.5-2.5 Hz in the absence of mechanical stimulation. Intrasomatic recordings revealed that such rhythmic bursting was driven by slow oscillations in membrane potential, the frequency of which was voltage sensitive and dependent upon the level of stretch applied to the receptor terminals of the AGR. 3. Autoactive bursting of the AGR originated from an endogenous oscillatory mechanism in the sensory dendrites themselves, since (i) during both steady, repetitive firing and bursting, somatic and axonal impulses were always preceded 1:1 by dendritic action potentials, (ii) hyperpolarizing the AGR cell body to block triggering of axonal impulses revealed attenuated somatic spikes that continued to originate from the two peripheral dendrites, (iii) the timing of burst firing could be phase reset by brief electrical stimulation of either dendrite, and (iv) spontaneous bursting continued to be expressed by an AGR dendrite after physical isolation from the GM1 muscle and the stomatogastric nervous system. 4. Although a given AGR in vitro could switch spontaneously from dendritic bursting to tonic firing and vice versa, exogenous application of micromolar (or less) concentrations of the neuropeptide F1 (TNRNFLRFamide) to the dendritic membrane could rapidly and reversibly switch the receptor firing pattern from repetitive firing to the bursting mode. Exposure of the somatic and axonal membrane of the AGR to F1 was without effect, as were applications of other neuroactive substances such as serotonin, octopamine and proctolin. 5. We conclude that, as for many oscillatory neurones of the central nervous system, the intrinsic activity pattern of this peripheral sensory neurone may be dynamically conferred by extrinsic modulatory influences, presumably according to computational demands. Moreover, the ability of the AGR to behave as an endogenous burster imparts considerable integrative complexity since, in this activity mode, sensory coding not only occurs through the frequency modulation of on-going dendritic bursts but also via changes in the duration of individual bursts and their inherent spike frequencies.

Vibration analysis of a glass harp by a finite-element method: Minor pitch change due to localized shaving of the bottom part

The finite-element method (FEM) was applied to analyze the vibration (inherent and the harmonic frequencies) of wine glasses (glass harp) as a musical instrument. FEM analysis for this problem was proven appropriate by confirming the coincidence between the experimental and analyzed inherent frequencies for several glass cups with different shapes. When using wine glasses as musical instruments, minute arrangement of the pitch is necessary. Even today, this is done by filling a certain quantity of water in the wine glasses. This method, however, is very troublesome because each time, just before a performance, a check has to be made to confirm that the correct water quantity had been filled in every vessel. Compounding the problem, the pitch sometimes changes during the performance because of water evaporation. In place of this water-filling method, minute pitch changes have been achieved by locally shaving a bottom part of each vessel. The pitch is found to decrease in proportion to the shaved glass quantity. The relationship between the shaved glass quantity and the changed pitch has been clarified experimentally and analytically through FEM analysis. With this procedure, the desired pitch can be obtained.

Intersegmental coordination in the lamprey central pattern generator for locomotion

Two theories have been formulated to explain how intersegmental coordination in the lamprey is produced. Both view the spinal locomotor CPG as a chain of coupled oscillators. One involves the development of a general mathematical framework that allows one to examine how differences in the inherent frequencies and differences in the kinds of coupling affect the phase lags along the chain. The other theory suggests a simple way in which constant phase lags along the chain can be produced from a chain in which the first oscillator has an inherently higher frequency and the coupling between oscillators is symmetrical. The goal of this review is to compare the two theories and to evaluate the available experimental data as it relates to both theories.

Co-ordination of pumping in isolated bovine lymphatic vessels.

1. Segments of bovine mesenteric lymphatic of varying diameter taken from different parts of the lymphatic tree were cut to 20 mm in length and set up so that measurements could be made of spontaneous isometric contractions. 2. There was considerable variability in frequency of spontaneous contractions but this was independent of resting tension. There was no significant correlation between lymphatic diameter and inherent frequency of contraction. 3. Isolated segments of bovine mesenteric lymphatic 70-80 mm in length were cannulated and set up in a three-compartment organ bath which allowed independent temperature control in each compartment. Pressure was recorded at inflow and outflow ends and experiments were video recorded. 4. Contractile activity was normally initiated at the end of the lymphatic maintained at the higher temperature and the contractile wave was propagated along the length of the vessel. 5. Propagation could occur either in the direction of valve orientation (orthograde) or retrogradely. The volume of fluid pumped was not significantly affected by the direction of propagation. 6. Perfusion of the central compartment with Krebs solution at 0-2 degrees C disrupted normal propagation and allowed the two parts of the lymphatic to contract at different frequencies although the two parts maintained an approximately 2:1 ratio. 7. Perfusion of the central compartment with 10 mM-heptanol also disrupted normal propagation but the rates on either side of the partition bore no harmonic relationship to one another. 8. These results suggest that relatively short segments of lymph duct have the ability to contract spontaneously and that their inherent frequencies are not determined by their position in the lymphatic tree. The results are consistent with the existence of electrical coupling along the lymphatic's length and they suggest that over distances of at least 80 mm independent pacemakers are capable of mutual entrainment at a frequency representing a compromise between the fastest and slowest components.

The free bending vibration of cylindrical tank partially filled with liquid and submerged in water

This paper studies the free bending vibration of cylindrical tank partially filled with liquid and submerged in water. The depths of liquid and water may be completely arbitrary. The exact calculating formulae of mode shape functions and inherent frequencies are deduced. The results can be gained by means of computer. The analysis shows that the effect of liquid and water on vibration of cylindrical tank is respectively equivalent to a generalized distributive mass attached to the tank.

Vibration of arbitrarily shaped membranes with elastical supports at points

This paper presents a new method for solving the vibration of arbitrarily shaped membranes with elastical supports at points. The reaction forces of elastical supports at points are regarded as unknown external forces acting on the membranes. The exact solution of the equation of motion is given which includes terms representing the unknown reaction forces. The frequency equation is derived by the use of the linear relationship of the displacements with the reaction forces of elastical supports at points. Finally the calculating formulae of the frequency equation of circular membranes are analytically performed as examples and the inherent frequencies of circular membranes with symmetric elastical supports at two points are numerically calculated.

Transverse vibration of rectangular plates elastically supported at points on edges

This paper studies transverse vibration of rectangular plates with two opposite edges simply supported, other two edges arbitrarily supported and free edges elastically supported at points. A highly accurate solution is presented for calculating inherent frequencies and mode shape of rectangular plates elastically supported at points. The number and location of these points on free edges may be completely arbitrary. This paper uses impulse function to represent reaction and moment at points. Fourier series is used to expand the impulse function along the edges. Characteristic equations satisfying all boundary conditions are given. Inherent frequencies and mode shape with any accuracy can be gained.

Couplings between normal modes studied by the correlation function. Duschinsky effect and fermi resonance

The dynamical information contained in a correlation function obtained by the Fourier transform of an electronic spectrum can be used to study strong intermode couplings, such as the Duschinsky effect (DE) and the Fermi resonance (FR). Both of them complicate the calculation of the correlation function by destroying its factorizability. In some particular cases, the DE can greatly simplify the form of the correlation function by concealing one of its inherent frequencies. The DE never leads to a beat or to a systematic decrease of the correlation function. A simple classical approximation for the correlation function which takes into account the Lissajous motion of the center of the wave packet, but does not allow for its deformation or spreading is found to be useful in a harmonic model. The FR leads to a beat in the correlation function which results from a periodic energy transfer from the active to the inactive mode. A practical method is given to extract the perturbed and unperturbed energies as well as the coupling matrix element of a FR from a low-resolution spectrum by Fourier transformation of just that part of the spectrum which corresponds to the quasidegenerate interacting states. The case of the B 2Σ u + state of CS 2 + is treated as an example.

DC Side Filtering Studies for the Pacific HVDC Intertie Voltage Upgrading

This paper describes studies conducted by the Los Angeles Department of Water and Power to evaluate the dc filter and smoothing reactor performance requirements necessitated by upgrading the Pacific HVDC Intertie system from ±400 kV to ±500 kV.1 The study objectives were to limit induced harmonic noise and ripple current to present levels and identify inherent resonant frequencies and the likelihood of their being excited. The performance of various filter configurations were analyzed under normal and contingency conditions. The study resulted in the definition of a filter configuration which would meet the stated objectives.

Computer analysis of mechanical activity of gastroduodenal junction in unanaesthetized dogs.

In four conscious dogs mechanical activity of the gastroduodenal junction was recorded with chronically implanted strain gauge transducers and induction coils. The data were evaluated by a computer. Analog circuits were used in order to reduce the data which were transferred to the computer. In the digestive state the contractions of the pyloric sphincter and duodenal bulb were correlated in such a way that the contractions of the duodenal bulb were inhibited when the gastric waves travelled across the antrum and that the bulb contracted once or twice when the peristaltic waves arrived at the gastroduodenal junction. However, the timing between pyloric and duodenal contractions was imperfect. Contraction maxima of the duodenal bulb often occurred before the pylorus was closed. This was due to the different inherent frequencies of the pyloric and duodenal contractions. In the interdigestive state the timing between the pyloric and duodenal contractions was as imperfect as during the digestive state. In phase III of the interdigestive activity, however, the strong antral contractions were regularly associated with inhibition of the duodenal bulb. This phenomenon can be interpreted as co-ordination between gastric and duodenal activity.

Design of Circuits for Coupling Power Amplifiers to Resonators

Four resonators and one buncher, each driven by a power amplifier through a coupling circuit, are being planned. The method by which the parameters of various coupling circuits have been calculated is discussed. Expressions for the parameters and inherent resonant frequencies are derived for some well-known coupling circuits.

STABILIZATION OF FLUTE INSTABILITY BY MEANS OF HIGH FREQUENCY FIELD

Flute instability is studied theoretically from the point of view of non-linear particle interaction under inhomogeneous high frequency field whose electric field component is parallel to confining magnetic. field. At first, kinetic equations with nonlinear term are solved by neglecting the non-linear term, i.e. by linear approximation. Using the linear solution, a first order non-linear solution is obtained and similarly a second order non-linear equation is solved. These solutions of the kinetic equations are utilized for induction of the dispersion relation of Flute instability. The interaction of the high frequency field with the instability are supposed to scour as a result of the additional induced particle motions paraller to the wave number Vector of the instability. Effects of the field on the instability are considered from the two points of view; one is attributed to the electron drifts and the other is owing to the periodic displacement of ions or electrons oscillating with the various inherent frequencies. The instability can be stabilized by the electron drifts whose velocities are larger than those of the ions drifted by the driving force of the instability and moreover may be easily stabilized by the additional periodic displacements of ions or electrons, superimposed on the above electron drifts. These displacement are owing to the high frequency field whose frequency is more resonant to half the ion or electron cyclotron frequency.