Highly enriched xenon124Xe /99.85%/ has been used for the experimental production of iodine123I by the /γ,n/ reaction. As the radiation source served a 30–45 MeV electron beam produced by a linear accelerator and converted by a tungsten converter to γ-radiation. The yield and radionuclidic purity of123I have been estimated, the content of isotopic impurities /124I and125I/ being for 30 MeV irradiations lower than 4×10−3%/.

Viktor Konstantinovich Voĭtovetskiĭ (Obituary), A P Aleksandrov, S T Belyaev, Yurii V Gaponov, D P Grechukhin, I I Gurevich, Yurii M Kagan, I K Kikoin, I L Korsunskiĭ, Yu F Pazhin, Nikolai A Chernoplekov

Summaries English This paper describes how the three Newtonian laws of dynamics are introduced in the higher grades of secondary schools in the Soviet Union. Particular attention is given to the treatment of the second Newtonian law. The authors reject the widely used method of introducing this law as an equation defining mass from which it is presented as a constant of proportionality between a statically measured force and acceleration. As an alternative, a method is described showing how the concept of mass can be introduced independently of the second Newtonian law. The accelerations resulting from the interaction of two bodies are considered as being a property of the bodies (inertia)‐‐quantified in the concept of mass. The second Newtonian law follows from experiments showing that for bodies of different masses submitted to the same force the products of their masses by their accelerations (ma) are equal and may serve as the measure of the force.