Nature of the “yield tooth” under torsion in plastic-deformed whiskers

The plastic torsion of whiskers with high Peierls barriers has been studied. As the samples for the studies we chose p-type germanium whiskers with <111> growth axis. The diameter of the whisker was (5–60)·10^–6 m and the gauge length was (1–4)·10^–3 m. The whiskers were dislocation-free in the initial state. Within the framework of the continuum model developed by us for the plastic deformation of whiskers under torsion, we analyze the anomalies of the torsional stress-strain diagram under different testing conditions and with preliminary deformation. The flow tooth during the torsion of a whisker is attributable to the nonuniform distribution of dislocations over the cross section of the whisker and high barriers to the dislocation motion.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–8, July, 1987.     

Diastereoselective hydrogenation of complexes of acetyldehydrophenylalanylmethionine and its esters with PdCl2

A new method, on principle, for the diastereoselective hydrogenation of dehydrodipeptides (DHDPs) and their esters entailing the utilization of the complex of the DHDP with PdCl₂ as the substrate was proposed. The formation of a certain conformation of the DHDP chain produced by the central atom of the metal complex-former permits the asymmetric synthesis of N-acetylphenylalanylmethionine with the optical yield up to 40%. The optical yield of the product depends both on the configuration of the methionine part of the peptide and on the bulk of the ester group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2828–2832, December, 1989.