Five-electrode field plethysmography technique for separation of respiration and cardiac signals.

Respiration monitoring by means of electric field plethysmography is influenced by cardiac activity, which represents an artefact although of physiological relevance itself. For a separation of respiration and cardiac signals, a portable plethysmograph was developed, which uses a fifth electrode in addition to the conventional tetrapolar electrode arrangement. The separation is attained by weighted software subtraction of two detected signals.

Rapid Detection of Salmonellae by Means of a New Impedance-Splitting Method.

An Impedance-Splitting method is proposed for the rapid detection of salmonellae in foods. The measuring System, BacTrac 4100, permits the registration of changes, caused by bacterial metabolism, not only of the impedance of the culture medium but also of changes in the ionic layers at the measuring electrodes, which has advantages in case of high salt concentrations. These changes are expressed as percentage decreases of the initial values, M-value and E-value, respectively.

Determination of ionic species formed during growth of Escherichia coli by capillary isotachophoresis.

The ionic species that are formed during the microbial growth of Escherichia coli were determined by capillary isotachophoresis as a function of the time of cultivation. This formation was indicated by the change in a sum parameter, the impedance of the nutrient broth, measured by a special electrode system. Based on the determination of the individual ions formed under the given conditions (identified as acetate, lactate, alpha-ketoglutarate, fumarate, ammonium and probably a simple amine), the change in conductivity was calculated and compared with that obtained by the impedance measurement of the bulk medium.

A method for the elimination of artefacts in electric field plethysmography of the lung.

The reliability of electric plethysmography for respiration monitoring is reduced by artefacts caused by the cardiac activity, by motions, electromagnetic cross-talk and others. For artefact suppression, a constant-current field-plethysmography technique is discussed which uses the voltage of an auxiliary electrode in addition to the conventional four-electrode arrangement. By means of a differential amplifier, a respiration signal is produced which is almost entirely free from heart artefacts, while the intensity of additional artefacts is suppressed.

[The effects of cold and deep freezing of the liver on its dielectric loss factor].

The dielectric loss factor d was measured on 130 porcine liver samples which were subjected to different cooling conditions. Immediately after slaughtering, all livers showed d less than or equal to 3. Subsequent cool storage caused continuous increases of d, which however does not provide reliable information about the storage time, since similar increases may result from mechanical treatment.