Forms of occurrence of plutonium in soils

The forms of Chemobyl plutonium were determined in soils with model laboratory and field experiments.     

Turing Machines Connected to the Undecidability of the Halting Problem

The problem of finding a Turing machine with undecidable halting problem whose program contains the smallest number of instructions is well known. Obviously, such a machine must satisfy the following condition: by deleting even a single instruction from its program, we get a machine with decidable halting problem. In this paper, Turing machines with undecidable halting problem satisfying this condition are called connected. We obtain a number of general properties of such machines and deduce their simplest corollaries concerning the minimal machine with undecidable halting problem.     

Solvability of the halting problem for certain classes of Turing machines

One method of proving that some Turing machine is not universal is to prove that the halting problem is solvable for it. Therefore, to obtain a lower bound on the complexity of a universal machine, it is convenient to have a criterion of solvability of the halting problem. In the present paper, we establish some of these criteria; they are formulated in terms of properties of machine graphs and computations.Translated from Matematicheskie Zametki, Vol. 13, No. 6, pp. 899–909, June, 1973.In conclusion, the author wishes to thank S. V. Yablonskii for discussing this work, and for a number of valuable comments, as well as O. B. Lupanov for suggestions.     

Behaviour of transuranium elements in the environment

The distribution and migration of Chenobyl plutonium have been studied in the ecosystem. Its behaviour is discussed.     

Migration of Chernobyl plutonium in soils

Various geochemically linked landscapes were studied for the distribution of Chernobyl plutonium in soils.