Ground-based intercomparison of two isoprene measurement techniques

International audienceAn informal intercomparison of two isoprene (C5H8) measurement techniques was carried out during Fall of 1998 at a field site located approximately 3 km west of Boulder, Colorado, USA. A new chemical ionization mass spectrometric technique (CIMS) was compared to a well-established gas chromatographic technique (GC). The CIMS technique utilized benzene cation chemistry to ionize isoprene. The isoprene levels measured by the CIMS were often larger than those obtained with the GC. The results indicate that the CIMS technique suffered from an anthropogenic interference associated with air masses from the Denver, CO metropolitan area as well as an additional interference occurring in clean conditions. However, the CIMS technique is also demonstrated to be sensitive and fast. Especially after introduction of a tandem mass spectrometric technique, it is therefore a candidate for isoprene measurements in remote environments near isoprene sources

High Pressure Effects on Superconductivity

The review is devoted to a discussion of the effects of high pressure imposed on superconducting materials. Low-temperature superconductors, high-temperature superconducting cuprates, and some unconventional superconducting compounds are investigated. Experimental as well as theoretical results regarding the pressure effects on Tc and other interesting properties are summarized.Comment: To be published in: "Frontiers in Superconducting Materials", Edt. A. Narlikar, Springer Verla

Arachnoid clearance of red blood cells

Labelled red blood cells were instilled intraventricularly in groups of dogs and monkeys for evaluation of transfer to the vascular compartment. Blood levels were minimal (5% of the original material) with low-pressure infusions. A large movement (above 25%) of the type originally described by Simmonds occurred with high-pressure intraventricular infusions, cisternal injections, or after the induction of intracranial hypertension. Large amounts of the label were released after cell lysis and accumulated in various tissues. Five to ten per cent of the instilled material was absorbed by the nasal lymphatic route in the dog and a significant local loss of red cells occured after posterior cisternal punctures. Simulated whole blood was useful in demonstrating arachnoid retention. Ventriculospinal washouts aided in the elimination of tagged cells only in the first 24 hours. Thereafter, the yield was small and the fluid requirement was unusually high

Ground-based intercomparison of two isoprene measurement techniques

An informal intercomparison of two isoprene (C₅H₈) measurement techniques was carried out during Fall of 1998 at a field site located approximately 3 km west of Boulder, Colorado, USA. A new chemical ionization mass spectrometric technique (CIMS) was compared to a well-established gas chromatographic technique (GC). The CIMS technique utilized benzene cation chemistry to ionize isoprene. The isoprene levels measured by the CIMS were often larger than those obtained with the GC. The results indicate that the CIMS technique suffered from an anthropogenic interference associated with air masses from the Denver, CO metropolitan area as well as an additional interference occurring in clean conditions. However, the CIMS technique is also demonstrated to be sensitive and fast. Especially after introduction of a tandem mass spectrometric technique, it is therefore a candidate for isoprene measurements in remote environments near isoprene sources