Preliminary Results from a Shuttle Mission to Measure the Heat Capacity of Confined Helium near the Lambda Point

We describe the preliminary results from a Shuttle mission to measure the heat capacity of helium confined within a stack of evenly spaced silicon plates at temperatures very close to the superfluid transition. Recently developed high resolution thermometry has substantially improved our ability to study dimensional cross-over effects in well-defined geometries. These effects have been of interest to theorists and esperimentalists for decades. The main part of the apparatus consists of a high purity copper calorimeter containing a stack of 408 silicon plates spaced 57 microns apart, and a pair of high resolution, fast response, paramagnetic salt thermometers with a noise level of < 10^–10 K in a 1 Hz bandwidth. The resolution of the heat capacity measurements was about 5 × 10^–9 K, allowing the finite size peak to be mapped in detail. In addition, wide range data containing information on the behavior of the surface specific heat was collected. The preliminary analysis shows fair agreement with theory. The results can also be combined with supplementary ground measurements on smaller length scales to perform additional tests of scaling predictions for cross-over to lower dimensional behavior.     

Effect of temperature and dissolved oxygen on biodegradation of nitrilotriacetate

The effect of temperature and dissolved oxygen on the rate of biodegradation of nitrilotriacetate (NTA) was examined in water samples collected from the Rur River. Biodegradation of NTA was first order with respect to NTA concentration over a concentration range of 50–1000 μg l⁻¹. First order rate constants showed a typical temperature dependency (temperature coefficient, Q₁₀ = 2) and biodegradation of NTA was observed over a temperature range of 2–24°C. The effect of temperature on the rate of NTA biodegradation was described by the Arrhenius equation, with calculated activation energies in the range reported for ordinary enzyme reactions. Biodegradation of NTA was also observed at low dissolved oxygen concentrations (0.3 mg l⁻¹), although at reduced rates compared to high oxygen concentrations (13 mg l⁻¹). Biodegradation of NTA was oxygen-dependent, suggesting an obligate oxygen requirement for the initial steps in NTA metabolism by natural microbial communities in surface waters. In general, our results indicate that NTA biodegradation will occur in natural waters under conditions of low temperature and low dissolved oxygen and also at low NTA concentrations.     

Mechanisms and products of ozonolysis of aniline in aqueous solution containing nitrite ion

The presence of nitrite ions (1 × 10⁻⁴ M) in the reaction medium affected the aqueous reaction of aniline (1 × 10⁻⁴ M) and ozone (2.07–2.15 × 10⁻⁴ M) at pH 6.25–10.65; o-, m- and p-nitroaniline were formed in addition to reaction products reported earlier. The combined yield of o- and p-nitroaniline was as high as 8%. Their yields were significantly higher at pH 6.25 and 7.25 than at pH 10.65 and carbonate species-inhibited their formation. The reaction mechanisms for the formation of the nitroanilines involves pernitrous acid, hydroxyl radical and nitrogen dioxide radical as the important intermediates.