In this study we have analysed the influence of temperature and time of storage and of repeated freezing on procalcitonin plasma concentrations ex vivo. We have also analysed the difference of procalcitonin concentrations in arterial or venous blood samples and the influence of different anticoagulation techniques on procalcitonin concentrations (serum, EDTA-, lithium-heparin-or citrate plasma). At room temperature (25 °C) a loss of procalcitonin plasma concentrations of 6.4% ± 2.6% (mean, 2 standard error of the mean) after 3 hours (4.6% ± 5.2% at 4 °C) and 12.3% ± 3.1% after 24 hours occurred (6.3% ± 5.0% at 4°C, n= 17 each). Comparing the procalcitonin concentrations of blood samples with different anticoagulants (n = 24 each), there was only a significant difference between procalcitonin concentrations in heparinized plasma and serum (+ 7.6%, difference of the mean). There was no significant influence of the blood sampling technique (arterial or venous line) and of repeated freezing/thawing cycles (up to 3 times) on the procalcitonin concentrations measured. Although the difference of sampling and storage of the blood on procalcitonin concentrations is not significant, multiple factors may act synergistically on the result of procalcitonin measurement. To keep variations of ex vivo conditions as minimal as possible, a standardized technique of anticoagulation, time and temperature of storage is recommended, e. g. the use of EDTA-plasma and storage at room temperature, when samples are measured within 4 hours after blood drawing.
Commercial strain gauges obtain a gauge factor of approximately 2 with a compensated temperature coefficient of resistivity (TCR). Therefore, material development for sputtered thin films with a high gauge factor and negligible TCR was conducted. The object for self compensated sensor materials is the combination of a semiconducting material (negative TCR) with high gauge factor and a metal (positive TCR) leading to a TCR close to zero. With nickel containing diamond-like carbon films (Ni-DLC or a-C:H:Ni) and Ag-ITO compounds zero crossing in TCR and gauge factors higher than 10 were achieved
Running-in is an important process for elastohydrodynamic lubricated contacts, which affect both service life and operating performance. However, the possibilities of monitoring running-in are still poor. Therefore, the properties of electrical contact impedance as a monitoring tool were studied by using an in-house made ball on disc apparatus. The contact impedance was monitored during run-in experiments with different initial surface roughness of the discs, different slide-to-roll ratios and with pure or additive containing paraffinic oil. The relationship between surface roughness parameters, contact resistance and contact capacitance was investigated. While the contact resistance seems to be affected by the parameter Rz, the contact capacitance seems more dependent on Rq. In addition, the experiments showed that surface active additives do not necessarily need to influence the contact impedance.
In most applied monitoring investigations using acoustic emission, measurements are carried out relatively, even though that limits the use of the extracted information. The authors believe acoustic emission monitoring can be improved by instead using absolute measurements. However, knowledge about absolute measurement in boundary restricted systems is limited. This article evaluates a method for absolute calibration of acoustic emission transducers and evaluates its performance in a boundary restricted system. Absolute measured signals of Hertzian contact excited elastic waves in boundary restricted systems were studied with respect to contact time and excitation energy. Good agreement is shown between measured and calculated signals. For contact times short enough to avoid interaction between elastic waves and initiating forces, the signals contain both resonances and zero frequencies, whereas for longer contact times the signals exclusively contained resonances. For both cases, aGreen's function model and measured signals showed good agreement.
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