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Biomedical subjects

A Scharmann

Publications and source records attributed to A Scharmann.

10 recordsLinked to original sources
PubMed1996

On-line laser-photometric monitoring of aerosol deposition in ventilated rabbit lungs.

A photometric technique was developed for on-line measurement of aerosol deposition in isolated, ventilated, and perfused rabbit lungs. A jet nebulizer was used for aerosolization of saline (hygroscopic particles) and di(2-ethylhexyl) sebacate (nonhygroscopic particles). Aerosol concentration (laser photometer, constructed for measurements in rabbit lungs) and flow rate (commercial pneumotachograph) were continuously monitored at the inlet of the tracheal cannula. Computer-assisted data processing allowed the breath-by-breath calculation of inhaled and exhaled aerosol mass, thus providing the deposition fraction. With the use of hygroscopic particles, however, this approach was hampered by the humidity-induced particle growth in the airways, leading to an overestimation of the aerosol concentration in exhaled air. This effect was corrected by an algorithm using a "particle growth factor" derived breath by breath from the photometer signal. To test the reliability of this approach, saline particles carrying technetium-99m label were aerosolized into rabbit lungs with the use of various ventilator settings, and the aerosol deposition was assessed in parallel by photometry and by radioactivity detection over the lung and over a trap in the exhaled-air circuit. Superimposable curves of cumulative aerosol deposition, with changes in kinetics dependent on the ventilator mode, were obtained. For a given ventilator setting, absolute values of the deposition fraction were 0.32 +/- 0.04 (radiotracer quantification) and 0.36 +/- 0.04 (photometry; means +/- SD; n = 4). We conclude that the presented laser-photometric technique allows reliable on-line monitoring of the deposition of both nonhygroscopic and hygroscopic aerosol particles in ventilated lungs.

Aerosols↗
PubMed1985

[Introduction to thermoluminescence--simple models].

Thermoluminescence comprises two fundamental processes, one proceeding at a constant temperature during the stimulation of the solid body by electromagnetic radiation or particle radiation, the other when the specimen is heated. The light emission during the rise of temperature can show several maxima and is called thermoluminescence glow curve. In some cases a thermally stimulated conductivity and a thermally stimulated emission of exoelectrons can be observed and correlated with thermoluminescence. The observations can be phenomenologically analyzed, not considering the physical processes of thermal activation and radiative recombination as well as the atomistic structure of the centres involved. Cinetic balance equations based on the energy band model are described. Some glow curves of thermoluminescence can be calculated in simple models, where the concentration of the charge carriers in traps, in permitted energy bands and in activators during the heat input are approximately determined.

Fluorescence↗
PubMed1984

Electron dosimetry with thermally stimulated exoelectron emission (TSEE).

The dependence of exoelectron emission from BeO and Al2O3 on primary electron energy has been measured over the 200 keV to 1.2 MeV range. Two types of measurements are made, firstly with the isotopes 90Sr + 90Y, 147Pm, 204Tl, and secondly for BeO with monoenergetic electrons from an accelerator. The TSEE response of covered BeO-dosemeters (cover of 7 mg cm-2 polyethylene) is independent from electron energies in the 200 to 700 keV range for constant equivalent doses (ICRP 21). The experimental results for uncovered TSEE-dosemeters and electron fluences are in agreement with calculations performed using a Monte Carlo program developed by Seltzer and Berger. The TSEE responses for electrons and photons in equivalent dose units are very similar. A lower detection limit of 20 mu Gy (absorbed dose in air) is found for this dosemeter.

Aluminum Oxide↗
PubMed1975

Investigations into the determination of the cytotoxicity of quartz dust by physical methods.

The methods of thermally stimulated luminescence (t.s.l), thermally stimulated exoelectron emission (t.s.e.e.), electron spin resonance (e.s.r), and infrared spectroscopy (i.r.) have been used to investigate whether the specific cytotoxic activities of SiO2 dust of various origins can be attributed to physical parameters. After interaction of toxic dusts with water an increase in the intensity of the t.s.l. peaks below room temperature has been detected whereas no effect could be observed in the case of inert materials. Dusts of weak cytotoxicity have been characterized by infrared absorption bands at 3610 cm-1 and 3685 cm-1. The results of the present studies emphasize the significance of silanol groups and adsorption properties in relation to the fibrogenic activity of quartz dusts.

Dust↗