Gamma-activation analysis of selenium at the electron accelerator “Mikrotron-ST”

In this work, an activation analysis of selenium under its irradiation with bremsstrahlung gamma radiation on a cyclic electron accelerator “Microtron-sT” with an energy of 21 MeV is carried out irradiation was performed at room temperature for 1 h, the gamma-ray intensity was ~ 5·1013 γ/s. Irradiation was carried out on two types of state of the samples (Se) in the form of granules of the (osch), weight 5-10 mg, and microparticles (powder) obtained by mechanical dispersion. Samples in the state of microparticles were suspended in distilled water, in separate polyethylene capsule. On each sample, after irradiation with bremsstrahlung gamma radiation, the spectra of quantum radiation of radionuclides were measured. The measurements were carried out repeatedly in order to observe a decrease in the activity of the samples and their energy gamma spectrum. From the results obtained, it can be seen that all radionuclides are formed on selenium nuclei with different mass numbers by reactions: (γ, n), (γ, p), (γ, 2n), (γ, p + n). The half-life of (T1/2) in identified radionuclides is within 3.9 minutes — 119.8 days. The energy of emitted quanta by radionuclides is equal to from 121.1 to 657 keV. The radiation intensity of radionuclide gamma rays is in the range: 0.25-99.0%.

Measurement of renal interstitial fluid pressure with polyethylene matrix capsules

The renal interstitial fluid pressure was measured in dogs from small chronically implanted solid capsules made of porous polyethylene matrix material (pore size approximately 60 mum). Tissue does not grow into the polyethylene and the matrix creates a permanent fluid-filled space in communication with the interstitium. The fluid pressure in the capsule matrix was measured from a tube leading from the capsule with an active servo-null pressure-measuring device. Renal interstitial fluid pressure measured from 28 hydropenic dogs averaged 6.1 plus or minus 0.51 mmHg (SE). Increasing oncotic pressure inside the capsule to 90 mmHg resulted in a small but significant increase in hydrostatic pressure inside the capsule of 3.3 plus or minus 0.46 mmHg. However, the hydrostatic pressure returned to control levels within 30 min. In vitro studies indicated that the pressure measured from the capsule was highly sensitive to change in surrounding hydrostatic pressure, but insensitive to change in surrounding oncotic pressure. Histological studies showed a small layer of connective tissue surrounding the capsule less than 100 mum thick in many areas. There was no evidence of inflammation or tissue rejection. It is concluded that the small chronically implanted polyethylene capsule is a reliable method for the measurement of renal interstitial fluid pressure.