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Results for “Analog-Digital Conversion”

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At least 379 records · Page 21Linked to original sources
PubMed1989

Analogue signal representation in the medial superior olive of the cat.

Temporal sound processing is likely to depend upon a delay line at a low level in the auditory pathways. We searched for such a delay line in the medial superior olivary nucleus of anesthetized cats. A remarkably pure sinusoidal neurophonic field potential could be recorded in the center of the MSO which was localized electrophysiologically as the point of the field potential polarity reversal and histologically by microinjection WGA-HRP through the recording microelectrode. Fourier analysis of the neurophonic potentials revealed increasing degradation by distortion products with distance from the MSO center. Neurophonic tuning curves indicated a similar frequency selectivity for individual recording sites as predicted by cochlear filter functions. Cross correlation of neurophonics recorded at different positions along the medio-lateral axis demonstrated the presence of a delay line, extending to over 0.6 ms. It is concluded that delay lines required for directional hearing and complex tone identification exist in the MSO.

Acoustic Stimulation↗
PubMedDate not supplied

Semiautomatic algorithm to remove resonance artifacts from the direct radial artery pressure.

Resonance artifacts introduced by the catheter-manometer system are removed from the direct radial artery pressure using a three-step algorithm. First, the fast-flush method is used to identify the natural frequency and damping coefficient of the monitoring system by digitizing and analyzing the pressure transient created by the flush. Second, resistor, capacitor, and inductor values are found for an RLC second-order model of the catheter-manometer system in use. Third, the algorithm predicts the undistorted radial artery pressure, removing the resonance artifacts by inverse-filtering the digitized monitored pressure waveform using the RLC circuit derived previously. The algorithm was implemented using a personal computer, but it could also be used without the computer by incorporating an analog-to-digital convertor and a microprocessor in the hemodynamic monitor.

Algorithms↗
PubMed1977

[Automatic analysis of gastrographies by means of optical digital equipment (author's transl)].

The present paper is concerned with problems of automatic analysis of radiograms, specially cinegastrographies. This study is connected with the utilisation of an interactive system including optical digitizer with its units of control and visualization. This system can explore the radiologic film in its current size of 30 X 40 cm. The particular interest of this application is extracting several parameters characterizing the size and the shape of the stomach. A middle axis can be extracted by computing, from this one a spatio-temporal diagram can be obtained. From this methodology of representation, several states of gastric motility could be characterized.

Analog-Digital Conversion↗
PubMedDate not supplied

[Simulator of cardiac activity signals].

Imitators of physiological signals are in need for production of electronic medical equipment and modeling the biological systems. The known imitators are rather intricate and incapable to control the output signal within a wide range. The imitator now offered allows to reproduce any signal that reflects the activity of a cardiovascular system under normal and pathologic conditions.

Analog-Digital Conversion↗
PubMedDate not supplied

[The role of digital storage in radiological studies based on fluoroscopic technics].

In recording radiological images obtained by fluoroscopic techniques on permanent support, digital storage, when compared with other methods, shows several interesting features, especially in order to reduce the X-ray dose and to allow for using economical hard copies. In the paper a system is described, for which it is possible to predict competitive cost in the near future; such system is based on a 512 X 512 X 6 bits digital memory, continuosly refreshed and on a software package oriented to handle radiological images. Examples of images referring to typical body segments (stomach, skull, chest) are reported.

Analog-Digital Conversion↗
PubMedDate not supplied

A comparison of gel-to-gel and skin measurements of electrode impedance.

Utilizing an automated test system, measurements of the 10-Hz impedance were made with electrode pairs joined gel-to-gel and electrode quartets on the skin of the backs of human volunteers. Two skin preparation procedures were examined. As a minimum skin preparation, the electrodes were applied to clean, dry skin from which body hair had been shaved if necessary. As a maximal preparation, the electrodes were applied after mild abrasion of the skin with fine emery cloth. Although the impedances measured for electrodes applied to mildly abraded skin correlated well with measurements made with electrodes of the same brand joined gel-to-gel, virtually no correlation was found if the electrodes were affixed to clean, dry skin.

Adult↗
PubMedDate not supplied

Automated measurement and frequency analysis of the pneumocardiogram.

The flow pneumocardiogram (PnCG), ie, measurement of cardiogenic gas movement in and out of the lung during apnea, was transduced by an in-line, high-gain pneumotachograph. A portion of the differentiated PnCG, the dPn/dt IJ wave, has been shown previously to correlate closely with left ventricular function. A simple analog device was designed and tested to measure the dPn/dt IJ amplitude on a practical beat-to-beat basis. Frequency-power spectral analysis showed the PnCG to be a low frequency phenomenon with the systolic component in the 9-to-10-Hz range. Appropriate band-pass filtering of the PnCG and its applicability as an intraoperative monitoring device are presented.

Analog-Digital Conversion↗