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Results for “Analog-Digital Conversion”

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PubMedDate not supplied

Confocal microscopy of the living eye.

Confocal microscopy is an imaging paradigm that allows optical sectioning of almost any material with increased axial and lateral spatial resolution and better image contrast. We have applied this technology to the study of the living eye of cats, albino rabbits, and humans. The technique allows in vivo, noninvasive, real time images of the eye at magnifications (630x) which allow resolution of anatomical detail at the cellular level. In this paper we report details of our current instrument techniques and some of our results. The past development, present state-of-the-art, and projected future advances and applications of this novel microscopy are discussed. Preliminary observations are reported for all layers of the cornea, the limbus, and wound-healing responses in single animals.

Analog-Digital Conversion↗
PubMed1989

Potassium channels in chick lens epithelium change with maturation.

Before hatching, chick embryos show a high incidence of inwardly rectifying potassium channels and calcium-activated potassium channels in the apical membrane of their lens epithelium. Subsequent to hatching, these channel types disappear while, at about the same time, a new calcium insensitive maxi potassium channel appears. This new channel shows several properties in common with the calcium-activated maxi potassium channels but is different in its conductive and gating properties.

Analog-Digital Conversion↗
PubMed1989

[Use of digital technics in the display of electromyography signals].

The use of digital techniques for the display of electromyographic signals often introduces grave errors in the visualization of the high frequency signal components. The causes for this can be quantitatively deduced from the technical principles of the systems. In the digital storage oscilloscope, the accuracy of reproduction is determined by the sampling rate and the memory capacity. In addition, there may be a considerable loss of quality in the visual display of systems using computer graphics despite accurate signal acquisition. Based on the quantitative analysis recommendations as to the technical equipment and use of digital neurophysiological systems are given.

Analog-Digital Conversion↗
PubMed1989

Frequency analysis of accommodation: single sinusoids.

We present an experimental frequency analysis of a neurological control system, the accommodation system, using single sinusoids. Also, by means of continual experimental calibration full coverage of one subject's dynamic range, we demonstrate an AC nonlinearity saturation, which probably lies in the motor-response portion of the system; in contrast to the switching-mode nonlinearity, which probably lies in the sensory-processing portion. We offer our findings as a basis for further models. In addition, our results can be compared with studies using multiple sinusoids and transients to document how the different aspects of the accommodation system are realized given their different input conditions.

Accommodation, Ocular↗
PubMed1989

A method of recording condylar movements and joint sounds.

A commercial tracking system has been adapted within the University of Melbourne, which is designed to track the movement of infra-red light emitting diodes (LEDs). The movement of the diodes was recorded by photosensimetric recording devices, and sent to a data recorder, then to a differential amplifier, and the signal stored on magnetic tape, or viewed on a cathode ray oscilloscope, or plotted on a chart plotter or an X-Y plotter. The equipment was used to track the movement of LEDs, which were secured to a lower arch face bow, which was in turn secured to the teeth via a universal joint, and an acrylic clutch. A method was established in a preliminary study, enabling recording of condylar movements in the sagittal plane, and results were presented for four subjects. Subsequently, condylar movements and joint sounds were recorded concurrently for two of these four subjects.

Analog-Digital Conversion↗
PubMed1989

Potential mapping in septal tachycardia. Evaluation of a new intraoperative mapping technique.

A recently developed computer program is capable of rapidly (less than 5 minutes) constructing a series of potential-distribution maps (PDMs) for every msec of a 4-second window of ventricular tachycardia (VT). This study was performed to assess the ability of a series of PDMs to localize the site of earliest activation of VT originating in the interventricular septum. In 12 dogs, 13 morphologies of VT were initiated with programmed electrical stimulation 3-6 days after anterior septal coronary artery infarction. VT was mapped with endocardial and epicardial unipolar electrodes with a multipoint, computer-assisted mapping system. PDMs were compared with activation-time maps, and the former correctly identified the site of earliest activation of all 13 VT morphologies. When PDMs were viewed in sequence on a computer monitor, the site of earliest activation was signaled by abrupt development of a negative potential of less than -3.0 mV. The initial negative point subsequently expanded, and the spread of this negative-potential field correlated with activation sequence. PDMs provide an accurate, unambiguous, rapid means of analyzing large numbers of electrograms acquired with multipoint, computer-assisted mapping systems.

Action Potentials↗
PubMed1978

Computerization of three-channel thrombelastograph.

A small-size and low-cost microcomputer using an Intel 8080 micro-processer is employed to provide real-time data collection and reduction of a three-channel electronic-readout thrombelastograph (TEG). Computed values of significant clotting parameters are obtained instantly allowing for rapid analysis and monitoring of many patients. Computer hardware was designed to optimize signal sampling rates, processing time and storage.

Analog-Digital Conversion↗
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↗