Setup For Simultaneous Measurements Research Articles

A new set-up for simultaneous high-precision measurements of CO<sub>2</sub>, <i>δ</i><sup>13</sup>C-CO<sub>2</sub> and <i>δ</i><sup>18</sup>O-CO<sub>2</sub> on small ice core samples

Abstract. Palaeoatmospheric records of carbon dioxide and its stable carbon isotope composition (δ13C) obtained from polar ice cores provide important constraints on the natural variability of the carbon cycle. However, the measurements are both analytically challenging and time-consuming; thus only data exist from a limited number of sampling sites and time periods. Additional analytical resources with high analytical precision and throughput are thus desirable to extend the existing datasets. Moreover, consistent measurements derived by independent laboratories and a variety of analytical systems help to further increase confidence in the global CO2 palaeo-reconstructions. Here, we describe our new set-up for simultaneous measurements of atmospheric CO2 mixing ratios and atmospheric δ13C and δ18O-CO2 in air extracted from ice core samples. The centrepiece of the system is a newly designed needle cracker for the mechanical release of air entrapped in ice core samples of 8–13 g operated at −45 °C. The small sample size allows for high resolution and replicate sampling schemes. In our method, CO2 is cryogenically and chromatographically separated from the bulk air and its isotopic composition subsequently determined by continuous flow isotope ratio mass spectrometry (IRMS). In combination with thermal conductivity measurement of the bulk air, the CO2 mixing ratio is calculated. The analytical precision determined from standard air sample measurements over ice is ±1.9 ppm for CO2 and ±0.09 ‰ for δ13C. In a laboratory intercomparison study with CSIRO (Aspendale, Australia), good agreement between CO2 and δ13C results is found for Law Dome ice core samples. Replicate analysis of these samples resulted in a pooled standard deviation of 2.0 ppm for CO2 and 0.11 ‰ for δ13C. These numbers are good, though they are rather conservative estimates of the overall analytical precision achieved for single ice sample measurements. Facilitated by the small sample requirement, replicate measurements are feasible, allowing the method precision to be improved potentially. Further, new analytical approaches are introduced for the accurate correction of the procedural blank and for a consistent detection of measurement outliers, which is based on δ18O-CO2 and the exchange of oxygen between CO2 and the surrounding ice (H2O).

Simultaneous measurement of electrical and thermal properties: Application to margarine

An experimental set-up for simultaneous measurement of thermal and dielectric properties of pasty materials, and in particular of margarine is proposed. The objective of the study was to observe simultaneously how the above mentioned properties change when margarine undergoes temperature changes within a temperature range that also encompasses its melting point. The PVDF pyroelectric sensor in combination with the plane plate capacitor was used for simultaneous measurement avoiding thereby problems arising from differences in both, sample's quantity and specific portion taken, the illumination level, heating, etc. As result of temperature variations both, the electrical and thermal properties of margarine were shown very sensitive to the structural changes. The reversibility of the modification process was observed. The results obtained with the set-up for simultaneous measurements were compared to those acquired by the methods capable of measuring each of the two properties separately.

A magnetic resonance-compatible experimental set-up for hyperthermia studies.

This study presents the development and testing of an experimental set-up for simultaneous measurements of pH (intracellular by MR and extracellular by fibre-optic pH meter), tumour bio-energetics (by MR), and core/tumour temperatures (by thermocouples) in tumour-bearing mice. Potential sources of measurement errors when using these techniques concurrently in an MR set-up are discussed. Emphasis is placed on simple practical solutions to these problems.