PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “COMPUTERS, ANALOG”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMed1975

A new method for automated detection of the R-on-T phenomenon.

The detection of premature ectopic beats coinciding with the T-wave of the antecedent beat is important for patient monitoring. In the method described here, the difficulties of direct measurement of QT time are avoided by evaluating the changes of QT time according to heart rate by use of a diode function generator. An analog circuit is used for comparing the computed QT time with the coupling interval of successive beats. In case of a R-on-T-phenomenon an alarm is given. The frequency of alarms is registered on a trend recorder. The methods is based on empirical equations which all contain a constant factor. Our investigations showed that the variability of this factor during longer periods of monitoring was small enough to allow sufficient exactness of the evaluation procedure.

Adult↗
PubMed1965

LIMITATIONS ON COMPLEXITY OF RANDOM LEARNING NETWORKS.

Randomly connected networks can be made adaptive, and thus able to "learn." Signal-to-noise considerations are shown to limit the maximum initial complexity which can learn. A higher order of complexity may be possible in multilayered structures which learn layer-by-layer; or if learning is possible during construction. Perception-like devices would appear not to be operative if of a high order of complexity.

Computers↗
PubMed1965

ON THE CONCENTRATION GRADIENT ACROSS A SPHERICAL SOURCE WASHED BY SLOW FLOW.

A model has been numerically analyzed to help interpret the orienting effects of flow upon cells. The model is a sphere steadily and uniformly emitting a diffusible stuff into a medium otherwise free of it and moving past with Stokes flow. Its properties depend primarily upon the Peclet number, Pe, equal to a . v(infinity)/D, i.e., the sphere's radius, a, times the free stream speed, v(infinity), over the stuff's diffusion constant, D. As Pe rises, and washing becomes more effective, the average surface concentration, C(s a) falls (Figs. 2 and 5) and the residual material becomes relatively concentrated on the sphere's lee pole (Figs. 2 and 4). Specifically, as Pe rises from 0.1 to 1, the relative concentration gradient, G, rises from 0.7 to 5.0 per cent and to the point where it is rising at about 8 per cent per decade; by Pe 1000, G = 22.1 per cent. From Pe 1 through 1000, G/(1 - C(s a)), or the gradient per concentration deficiency remains at about 26 per cent suggesting that G approaches a ceiling of about 26 per cent. Also from Pe 1 through 1000, the average mass transfer co-efficient nearly equals that previously calculated for spheres maintaining constant surface concentration instead of flux. The complete differential equation without approximations, the Gauss-Seidel method, and an approximation for the outer boundary condition were used.

Biophysical Phenomena↗
PubMed1990

Accuracy of digital Holter monitoring of extent and duration of ischemic episodes compared to analog recording.

Analog amplitude-modulated Holter devices are in widespread use for arrhythmia detection, but their reliability remains questioned for ST-segment analysis. In contrast, recently developed digital Holter devices immediately digitize and analyze the electrocardiogram (ECG) on-line and may therefore be more reliable for ST-segment analysis. To test this hypothesis, the results of digital, on-line, 2-channel ST-segment analysis were directly compared to those of analog amplitude-modulated recordings in identical leads (CM5 and CM3), using a stripchart recorder meeting the American Heart Association specifications as the standard. Thirty-five patients (25 with coronary artery disease and 10 control subjects) underwent graded treadmill exercise testing. The reference ECG mean value for ST-segment depression in CM5 was -1.4 +/- 1.2 mm and in CM3 -0.5 +/- 1.2 mm. For digital analysis, the mean values and correlation coefficients for CM5 were -1.5 +/- 1.1 mm (r = 0.97) and for CM3 -0.8 +/- 1.3 mm (r = 0.93). For analog recording, the results for CM5 were -2.1 +/- 1.7 mm (r = 0.88) and for CM3 -1.3 +/- 1.9 mm (r = 0.85). The mean duration of ST-segment depression with the reference ECG was 7.1 +/- 4.1 minutes. Digital Holter showed a significantly better agreement (7.4 +/- 4.4 min, r = 0.97) than analog Holter (9.6 +/- 5.6 min, r = 0.84). Because analog amplitude-modulated Holter recordings overestimated the degree and duration of ischemic episode, digital, on-line and full disclosure devices should be preferred to assess myocardial ischemia.

Algorithms↗
PubMed1980

An analog patient model derived from computed tomograms for three-dimensional radiotherapy planning.

An analog model of the part of a patient's body containing a tumor is constructed by drawing anatomical contours obtained from computed tomograms on a set of transparent plastic sheets. The coverage of radiotherapy fields in the patient is visualized in three dimensions using the model and the light beam from the radiotherapy machine or a simulator. A clinical example is presented.

Humans↗