Mesomechanics of plastic deformation and fracture of partially crystalline polyethylene

From the standpoint of physical mesomechanics, we have investigated plastic deformation mechanisms and the mechanical properties of partially crystalline polyethylene. We show that from the very beginning, plastic deformation occurs at the mesoscopic level. Fracture is preceded by fragmentation of the material. The observed stages of the process of plastic deformation of polyethylene are qualitatively similar to the stages of this process for metallic materials. The effect of electron bombardment on the mechanical properties of polyethylene is explained by the size reduction in the mesoscopic substructure formed on plastic deformation. Tomsk Polytechnical University. Zhilin University, People’s Republic of China. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 48–53, January, 1997.     

Superconductivity in the BaPb1−x Bi x O3 system

Superconductivity properties of the BaPb_1−x Bi _x O₃ system have been investigated by precise measurements of electrical resistivity and Hall coefficient in specimens prepared by the hot press technique. Sharp superconducting transitions have been observed in those specimens, indicating the homogeneities of the specimens thus prepared. superconductivity has been observed for 0.05<x≦0.35 and a maximum critical temperature of 11.7 K has been observed atx=0.25. The carrier concentration deduced from the Hall coefficient has been found to show nearly the samex dependence as does the critical temperature. The upper critical field has been determined from the magnetic field dependence of the lowcurrent-density resistivity. Discussions are given about the superconductivity in the BaPb_1−x Bi _x O₃ system on the basis of the experiment results.     

On the quantum density of states and partitioning an integer

This paper exploits the connection between the quantum many-particle density of states and the partitioning of an integer in number theory. For N bosons in a one-dimensional harmonic oscillator potential, it is well known that the asymptotic (N→∞) density of states is identical to the Hardy-Ramanujan formula for the partitions p(n), of a number n into a sum of integers. We show that the same statistical mechanics technique for the density of states of bosons in a power-law spectrum yields the partitioning formula for p^s(n), the latter being the number of partitions of n into a sum of sth powers of a set of integers. By making an appropriate modification of the statistical technique, we are also able to obtain d^s(n) for distinct partitions. We find that the distinct square partitions d²(n) show pronounced oscillations as a function of n about the smooth curve derived by us. The origin of these oscillations from the quantum point of view is discussed. After deriving the Erdos-Lehner formula for restricted partitions for the s=1 case, we use the modified technique to obtain a new formula for distinct restricted partitions.     

Strangeness production in the Dual Parton model

Production of strange mesons and baryons is studied in a Monte Carlo Dual Parton model for hadron-hadron, hadron-nucleus and nucleus-nucleus collisions with standard strangeness suppression in the chain fragmentation and enhanced strangeness (up to a SU(3) symmetric sea) at the sea chain ends. Additionally, production from the sea has been introduced into the chain formation process with the same probability as for the q→qq branching within the chain fragmentation. Rapidity distributions and multiplicity ratios are in reasonable agreement with recent experimental data.     

Addition von phosphanen an chelat-biscarben-liganden- ein weg zu carben-ylid-komplexen

A biscarbenetungsten complex, cis-(CO)₄W[C(OEt)CHPhCHPhC(OEt)], is modified to its carbene-ylid derivative via addition of one equivalent of trimethylphosphane.