PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Amplifiers, Electronic”

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 19 recordsLinked to original sources
PubMed1978

Simultaneous blank correction in a turbidimetric continuous flow system for immunochemical quantitation of plasma proteins.

By shortening the reaction time by polymer enhancement, it was possible to introduce a line for automatic blank correction in a turbidimetric continuous flow system. The turbidity resulting from the reaction was measured by a simply constructed photometer, the serum turbidity being subtracted by the reference photoelectric cell and the resulting net signal amplified by means of the recorder's stepwise electronic amplifier. Serum transferrin values obtained by this method correlated well with values obtained by estimating blank in separate runs, and with values given be electroimmune assays.

Autoanalysis↗
PubMed1978

The deaf doctor.

Cardiopulmonary auscultation and considerable difficulty in hearing lecturers are major problems which face prospective deaf medical students. As a result, their opportunities for obtaining a medical degree have been, until recently, severely limited. However, rapid advance in electronics research have now made available to them a suitably amplified electronic stethoscope and a free-field radio transmission system.

Clinical Competence↗
PubMedDate not supplied

[Hysterosalpingography in sterility].

From 1967 to 1975 the authors performed 500 hysterosalpingographies in 851 women examined for sterility. Hysterosalpingography was carried out under the diascopic control of an electronic amplifier and a tele-monitor. As a contrast medium only the water-soluble Joduron U-S (Cilag) was used. In 286 women (57%) primary sterility and 214 (43%) secondary sterility were established. Radiographic analysis revealed 209 anomalies of the uterus, 114 of which related to hypoplastic uterus. In 286 women with primary sterility there was occlusion of one or both tubes in 62 cases (21.67%) and the sactosalpinx of one or both tubes in 48 cases (16.78%). In 214 women with secondary sterility, there was occlusion of one or both tubes in 66 cases (31.30%) and the sactosalpinx of one or both tubes in 48 cases (22.42%). In 500 hysterosalpingographies the intravasation of the contrast medium into the venous system occurred in 23 cases (4.60%) but there was not a single case of unatoward side-effects. Sixty-six women became gravid 1--6 months after hysterosalpingography, without the use any other kind of therapy.

Adult↗
PubMed1992

Speech recognition in noise when wearing amplitude-sensitive ear-muffs.

Speech recognition in background noise when wearing amplitude sensitive (non-linear) ear muffs was studied in the laboratory in 15 young normal-hearing test subjects. Low-redundancy sentences were presented from a loudspeaker in a background noise level of 70 dB (A) and the speech-to-noise (S/N) ratio yielding 50% correctly recognized words was determined. Three background noise spectra were tested: white noise, low-pass filtered noise (-12 dB/octave) and high-pass filtered noise (12 dB/octave). Five listening conditions were used: no protectors, a pair of normal ear-muffs, a passive amplitude-sensitive ear-muff and two types of electronic amplitude-sensitive ear-muffs. An ANOVA shows that speech recognition is significantly influenced by type of hearing protector and by noise spectrum. The interaction between these factors was not statistically significant. In general, the test subjects obtained somewhat better speech recognition thresholds in noise when wearing electronic amplitude-sensitive ear muffs than without muffs, whereas the opposite was true for the passive amplitude-sensitive and the normal ear muffs.

Acoustic Stimulation↗
PubMed1975

Combined device for measurement of the duration of the cardiac cycle and stimulation synchronized with the cardiac cycle.

A simple device for measuring the momentary cardiac frequency (i.e. a value proportional t-r the length of the time interval between two cardiac contractions) is worked out using a capacitoo transducer consisting of two capacitors and an electron control circuit. The sequence of the charging, indication of the voltage and the discharge of the capacitors is effected by a relay circuit. A random signal characterizing the cardiac cycle can be used as input signal, such as: ECG, pulse signal, signal of the blood pressure transducer, etc. At a definite moment of the cardiac cycle the device produces a synchroimpulse. This makes it possible, by regulating the delay between the triggering and the stimulating impulses of an external stimulator, to realize a regime of synchronized stimulation, i.e., the stimulating impulses to coincide with a preliminarily given moment after the beginning of the cardiac cycle. The output of the device is connected with a standard recording device with sufficiently large input resistance. The transistor electronic circuit is connected to the supply or to an autonomous source. The dimensions of the device are 20 X 12 X 10 cm, its weight is about 2 kg.

Amplifiers, Electronic↗
PubMed1992

A piezoelectric respiratory monitor for in vivo NMR.

This report describes a simple electronic device employing a piezoelectric element which serves as a sensitive detector of motion. The device is useful as a monitor of respiratory motion for nuclear magnetic resonance animal experiments in vivo. It can also provide a trigger pulse for respiratory gating experiments.

Amplifiers, Electronic↗
PubMed1991

Attenuation of hearing protectors at 85 dB SPL investigated by commercial "insertion gain" method.

Attenuation of hearing protectors is conventionally measured as the difference between the subject's pure-tone hearing threshold with, and without, hearing protection under free field conditions (loudspeaker) in a sound attenuated (an-echoic) room. This REAT procedure is not objective as it involves the response of a subject. The attenuation can not be measured at noise hazard levels: > 85 dB SPL. Commercial computerized "insertion gain" equipment has recently been developed to improve the individual fitting of hearing aids. By "insertion gain" method a slender silicone probe-tube connected to an outside microphone, is inserted in the ear canal, registering the sound pressure level in front of the tympanic membrane. Thus one can objectively register the sound pressure level difference (gain) obtained close to the tympanic membrane with a given hearing aid in a non-attenuated room. We wanted to study whether the same procedure could be used to assess the attenuation of hearing protectors at noise hazard levels with acceptable measurement variability. With a commercial computerized "insertion gain" equipment (IGO-HAT 1000. Madsen Electronics) we registered the "insertion loss", the difference in sound pressure level measured < 5 mm in front of the tympanic membrane for 20 consecutive sessions (fittings) in the same subject with versus without the same hearing protector. Below 6000 Hz standard deviations were remarkably low--around 2 dB--for the two protectors tested.

Acoustics↗
PubMed1991

Computer-controlled attenuator.

Various possibilities for applying electronic computer-controlled attenuators for the automation of physiological experiments are considered. A detailed description is given of the design of a 4-channel computer-controlled attenuator, in two of the channels of which the output signal can change by a linear step, in the other two channels--by a logarithmic step. This, together with the existence of additional programmable timers, allows to automate a wide range of studies in different spheres of physiology and psychophysics, including vision and hearing.

Amplifiers, Electronic↗
PubMedDate not supplied

Electronic cell volume (coulter volume) distribution of vaginal-cervical cytology samples.

Peripheral blood and buccal cells were used as "model" cell populations to indicate where in the electronic cell volume (ECV) spectrum the individual cell populations of vaginal and cervical irrigations would appear. Four clinical samples each representing a different stage of abnormality were evaluated and compared with the "model" cell populations. The pattern was the same for all of the clinical samples and correlated with the blood and buccal cell populations. Only two distinct ECV populations were observed, the inflammatory cells and the epithelial cells. There was no difference in pattern of any of the volume distributions to indicate abnormality to any degree.

Amplifiers, Electronic↗
PubMed1975

Directional microphone in hearing aids. Effects on speech discrimination in noise.

This study was designed to investigate the amount of directionality among three directional aids of different brands and to compare speech discrimination ability of hearing-impaired persons using directional and nondirectional hearing aids in competing background noise. For each hearing aid under study, the full-on gain curves were obtained at 45, 135, 225,, and 315 degree azimuths in an anechoic chamber. Thirty-two hearing aid users were included. Discrimination ability was assessed, using commercially available W-22 disc recordings. Findings indicate directionality varies among directioalaids. The hearing aid that shows the greatest directional effect was found to provide the listeners with best speech discrimination ability under relatively difficult listening conditions. However, it is inadvisable to recommend just any directional aid without careful evaluation of its directional capability under competing noise.

Acoustic Stimulation↗
PubMed1978

Clinical rationale for using an overhead speaker in evaluation of hearing aids.

A variable that has received little attention in the psychoacoustic evaluation of the hearing aid is the position of loudspeakers with respect to the listener, particularly the azimuth of the loudspeaker, which is used for presenting the competing message. In the past, a variety of locations have been used, some of which can bias the outcome of the evaluation. For this reason, this article suggests the use of an overhead speaker to deliver the competing signal. The overhead placement provides a neutral location that is highly desirable for making reliable repeated speech performance comparisons. In addition, the overhead speaker can be easily adapted to the testing environment while it produces the effect of surrounding the listener with the competing signal.

Amplifiers, Electronic↗