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Biomedical subjects

D Sadeh

Publications and source records attributed to D Sadeh.

27 records · Page 2Linked to original sources
PubMed1983

An advanced non-invasive technique for the recording of His bundle potential in man.

A new method for external recording of the His bundle electrical activity is described. Four hundred standard ECG waveforms were recorded and digitized at 1.28 kHz (8 bit resolution) and averaged with the aid of a CDC 6600 computer to reduce the random noise. A cross correlation function, which operates in the frequency domain using the Fast Fourier Transform algorithm, was employed to extract fiducial synchronizing marks for the waveforms alignment (triggering). Waveforms were filtered with a digital bandpass filter (30 Hz and 250 Hz low and high cut off frequencies respectively). The activity of the His bundle which was thus obtained was present on an isoelectric line, with signal amplitude of 4 to 7 microV. A strong correlation (r = 0.95, n = 10) was found between the HV intervals and the HQ intervals obtained from intracardiac electrograms and the new technique. It was concluded that the new method is convenient, reliable and can be successfully applied for the management of patients with various problems in their cardiac conducting system.

Adolescent↗
PubMed1979

Novel enzyme immunoassay for 17 beta-estradiol.

A novel approach to the enzyme immunoassay of analytes is presented and illustrated by demonstration of an estradiol assay. The assay depends on the competitive binding of estradiol and estradiol-DNP conjugate to immobilized anti-estradiol. The amount of estradiol-DNP bound is inversely proportional to the amount of free estradiol, and is measured through the use of peroxidase-labeled anti-DNP antibodies. The assay gives a dose-response curve from 10 pg/tube to 450 pg/tube and shows satisfactory correlation with radioimmunoassay.

Estradiol↗
PubMed1978

Geotropism of hornet comb construction under persistent acceleration.

Social wasps (Vespinae) are insects which build in a precise geotactical orientation. The effect of persistent acceleration on comb construction by Oriental hornet (Vespa orientalis) workers was assessed experimentally within breeding boxes of various size and shape. Groups of hornets at the building phase were subjected to a centrifugal and gravitational force with a resultant ranging between 26 degrees and 45 degrees. The comb construction within such boxes was compared to that within control boxes under ordinary gravitational pull. It was found that: a) juvenile hornets (1-2 days of age) placed in quasi-rectangular boxes built in the direction of the resultant force; b) juvenile and adult hornets (3-7 days of age) placed in spherical shaped containers also built in the direction of the resultant force; c) adult hornets who had spent their first days of life in a stationary rectangular box, apparently learned the direction of the gravitational force and "tried" to build in this direction when exposed to a centrifugal force; d) adult hornets made to spin in quasi-rectangular boxes tilted in the direction of the calculated resultant force built in the direction of the resultant. These results suggest that hornets learn the direction of the gravitational force during the first days of life and that geometrical cues within the breeding box enable them to build in the direction of the force to which they have become habituated. From the standpoint of geometric cues, only the roof of the breeding box is of critical importance.

Aging↗
PubMed1977

Hornet ventilation noise: rhythm and energy content.

A new technique is used to measure the hornet's wing movement. It enables one to measure precisely the frequency of this movement, even in the presence of spurious 'noise'. This autocorrelation technique revealed that the hornet's wing stroke is divided into 3 smaller strokes when they are tired. The energy content in each stage can be measured using the autocorrelator.

Animals↗
PubMed1975

Direction finding by hornets under gravitational and centrifugal forces.

The effect of centrifugal and gravitational forces whose resultant ranged between 26 degrees and 45 degrees on comb construction by hornet workers was assessed experimentally. Comb construction by hornets exposed to centrifugation at 1 to 2 days of age differed from that of hornets similarly exposed at 3 to 7 days of age. Juvenile hornets built their cells in the direction of the resultant force, whereas adults resisted the centrifugal force and tried to build in the direction of the gravitational force. Juveniles started their comb from the side walls, whereas adults started from the roof, as did nonspinning, control hornets. The findings suggest that hornets rapidly learn the gravitational force during the first days of life, and that they are aided by geometric cues of the breeding box to build in the direction of the force to which they had become habituated.

Age Factors↗
PubMed1973

The excess radioactivity of trypsin mixtures.

The radioactivities of mixtures of trypsin and HB(3)O(3) or LiCl have been measured and compared with the radioactivity of the constituents. No evidence was found for the production of heavy particles, as had been previously reported, neither were the excess counting rates of the mixtures over that of its constituents as large. The residual excess radioactivity was about four orders of magnitude smaller than that published, yet was still statistically significant, consisting mainly of electrons having a maximum energy less than about 400 keV. The excess radioactivity of a mixture of trypsin and LiCl had a probable half-life between 5 and 46 days. Possible mechanisms for these excesses are discussed.

Absorption↗
PubMedDate not supplied

Modeling of the heart's ventricular conduction system using fractal geometry: spectral analysis of the QRS complex.

Many biological systems having one or more characteristics that remain constant over a wide range of scales may be considered self-similar or fractal. Geometrical and functional overview of the ventricular conduction system of the heart reveals that it shares structures common to a tree with repeatedly bifurcating "branches," decreasing in length with each generation. This system may further simplify by assuming that the bifurcating and decreasing process is the same at any generation, that is, the shortening factor and the angle of bifurcation are the same for each generation. Under these assumptions, the conduction system can be described as a fractal tree. A model of the heart's ventricles which consists of muscle cells and a fractal conduction system is described. The model is activated and the dipole potential generated by adjacent activated and resting cells is calculated to obtain a QRS complex. Analysis of the frequency spectrum of the QRS complex reveals that the simulated waveforms show an enhancement in the high frequency components as generations are added to the conduction system. It was also found that the QRS complex shows a form of an inverse power law, which was predicted by the fractal depolarization hypothesis, with a highly correlated straight line for a log-power versus log frequency plot with a slope of approximately -4. Similar results were obtained using real QRS data from healthy subjects.

Computer Simulation↗