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Cosmic ray produced ^P(t_=14.3days;E_=1.71MeV) is a powerful tracer of physical and biological processes and the short time scales of atmospheric and upper ocean P cycling. In spite of their tremendous potential for tracing processes involving phosphorus in the environment, the very low activities in nature have impeded their use in biogeochemistry. In order to determine the low-level beta activities of ^P in nature, sample concentration and/or extraction from large volumes of samples are required with a low-level β counting in the field. Preconcentration of the activity in aerosol is achieved here by various concentrating methods. Low-level β counting is achieved by liquid scintillation counting and low background counting. The result of measurement of the activity in aerosol by liquid scintillation counting at Shizuoka University (34°58'N, 138°24'E) ranged from 0.0010±0.0002 to 0.003l±0.0002dpm / m^3 (dpm : disintegrations per minute). Decay-curve in low background counting confirms the existence of ^P(t_ = 25.3days;E_ = 0.25MeV).

The author attempted to establish a new method of measuring water content in the brain tissue using tritiated water and a liquid scintillation counter. Approximately 50 mg of brain tissue was taken, put into a 1 ml disposable syringe and squeezed out in a centrifuge tube containing 2.5 ml of methylalcohol. This was then subjected to supersonication (by a supersonication bacterial homogenizer T-A-4201) for 3 minutes to prepare brain tissue homogenate. The homogenate was mixed in a glass vial with 20 ml of previously prepared scintillator for liquid scintillation counting. The author prepared six kinds of scintillators and investigated which scintillator was the best one in efficiency, and reproducibility for counting. The six kinds of scintillators were as follows: 1) Simple scintillator which was composed of one liter of toluene, 5 g of PPO and 300 mg of DM-POPOP. 2) Simple scintillator with 4 % Cab-o-sil. 3) Simple scintillator with 500 ml of Triton X 100. 4), 5) and 6) were the same composition as scintillators 1) to 3), but also had 50 ml of Soluene 100 added. The author concluded that the most suitable scintillator was No. 5 which was composed of simple scintillator, Cab-o-sil and Soluene 100. Next, the author examined the accuracy of this method in measuring the water content of brain tissue. Cold induced edema was produced in the right parietal region of rats. Half of the animals were untreated. The others were treated with 0.8 mg/Kg of dexamethasone after cold injury. The water content was calculated as follows: Ratio of increased water cpm/g of tritiated water in content in the injured = the injured hemisphere / cpm/g of tritiated water in ×100 hemisphere the non-injured hemisphere In the untreated animals, the water content in the injured side increased significantly from the control of 100.7±0.5 to 105.5±0.8 at 24 hours after cold injury. (Values are mean±S.D.) In the dexamethasone treated group, the water content in the injured side decreased significantly to 101.0±0.7 at 24 hours after injury. From these results, the author concluded that this new method might be an accurate, reproducible, unique and useful one for measuring the water content of brain tissue.