CORRIGENDUM: Phase transition in the two-dimensional frustrated x-y model: scaling equations
The author establishes scaling equations for the two-dimensional x-y model with weak frustration using the electrostatic analogy of Kosterlitz and Thouless. In the limit of small disorder he finds a shift in the critical temperature Tc(x)-Tc(0)=-(Jx/kB)(2 pi 2- pi /2 ln 2x) and the exponents are unchanged from the pure values.
Bond disorder enhances the information transfer in the polar flock
Collections of self-propelled particles (SPPs) exhibit coherent motion and show true long-range order in two-dimensions. Inhomogeneity, in general, destroys the usual long-range order of the polar SPPs. We model a system of polar SPPs with inhomogeneous interaction strength or bond disorder. The system is studied near the order-to-disorder transition for different strengths of the disorder. Our numerical simulation indicates that the nature of the phase transition changes from discontinuous to continuous type by tuning the strength of the disorder. The bond disorder also enhances the ordering near the transition due to the formation of a homogeneous flock state for the large disorder. It leads to faster information transfer in the system and enhances the systems’ information entropy. Our study gives a new understanding of the effect of intrinsic inhomogeneity in the self-propelled particle system.
One hundred percent tumor induction in mouse skin after repeated beta irradiation in a limited dose range.
Repeated beta irradiation of the backs of mice three times a week with radiation doses of 250 to 1180 cGy per exposure induced 100% incidence of tumors. The incidence of skin tumors appeared to be determined by the total number of repeated exposures in this dose range. An abrupt delay in tumor emergence was observed when the radiation dose was reduced from 250 to 150 cGy per exposure, indicating the existence of a critical threshold. Mouse skin resembles human skin rather than rat skin in its response to radiation.