Quantifying the contribution of nitrification and denitrification to the nitrous oxide flux using 15N tracers

Microbial transformations of nitrification and denitrification are the main sources of nitrous oxide (N2O) from soils. Relative contributions of both processes to N2O emissions were estimated on an agricultural soil using 15N isotope tracers (15NH4+ or 15NO3-), for a 10-day batch experiment. Under unsaturated and saturated conditions, both processes were significantly involved in N2O production. Under unsaturated conditions, 60% of N-N2O came from nitrification, while denitrification contributed around 85-90% under saturated conditions. Estimated nitrification rates were not significantly different whatever the soil moisture content, whereas the proportion of nitrified N emitted as N2O changed from 0.13 to 2.32%. In coherence with previous studies, we interpreted this high value as resulting from the decrease in O2 availability through the increase in soil moisture content. It thus appears that, under limiting aeration conditions, some values for N2O emissions through nitrification could be underestimated.     

Production of separation-nozzle systems for uranium enrichment by a combination of X-ray lithography and galvanoplastics

X-ray lithography using synchrotron radiation has been applied in a multi-step process for the production of plastic moulds to be used in the fabrication of separation nozzles by electrodeposition. For characteristic dimensions of a few microns a total height of the nozzle structure of about 400 μm has been achieved. Structural details of about 0.1 μm are being reproduced across the total thickness of the polymer layer. The surface finish of metallic separation nozzles produced by electrodeposition was equivalent to the high quality of the polymer surface. The separation-nozzle systems fabricated by the described method allow an increase by a factor three of the gas pressure in separationnozzle plants as compared to the present standard. This results in considerable savings in the enrichment of ²³⁵U for nuclear power production.     

亚甲蓝分光光度法测定水中阴离子表面活性剂的探讨

对水中阴离子表面活性剂的测定方法做了一些探讨改进，并用改进方法和目标法分别对已知样和自配样进行了测定比较，结果标准偏差〈1％，效果较好。     

Relationships between dissolved free amino acids,chemical composition and growth of the marine diatom Chaetoceros debile

The release of dissolved free amino acids in axenic batch cultures of the diatom Chaetoceros debile during different growth phases was studied during the late summer of 1982. Variations due to ASP, HIS, ALA, SER, THR, PHE+NH⁴, LEU and ORN were observed. The proportions of each amino acid differed according to growth phase. Maximum release and accumulation in the medium, corresponding to a rise ranging from 10^-8 to 10^-6 M, occurred at the transition between the exponential and stationary phases, and coincided with a shift in the intracellular protein and carbohydrate concentrations, and in the chlorophyll: phaeophytin ratio. It is suggested that zooplankton grazers can benefit from the accumulation of phytoplankton standing stock and nutritious compounds at times when the concentration of extracellular amino acids is high enough to trigger chemosensory detection of algal food; i.e., at the end of the exponential growth phase.